Frank996

Quick question, I have started to get a quite loud 'ticking' sound from the engine - no OBC messages and/or loss of power or change of 'feel' if it makes sense...

I thought at first it came from the back right wheel as I only heard it if the window was opened and close to a wall when driving (kind of an echo). I parked the car after 90 mins of driving or so, went out and heard it came from the right side of the enginr (or so I think)

The engine bay fan also came on but I did push the car a little as we did some mountain driving today and the above 'ticking' came afterwards...

I'll check and see if it has now stopped after "cooling" down the engine over night.

I have a 4-5 hour drive back home so any pointers are highly appreciated indeed.

Any ideas?

z3mcoupe

The DFI engines are quite noisy and they 'tick'. Is this a new noise you haven't heard before from the engine?

Frank996

Thanks for your reply z3mcoupe,

Tbh, I'm not 100% sure if it's been there before or not, but I'm now so focused on it so I (or at least on my head) think it's "new".

My partner had not notised anyhing different but she is not even sure where the engine is placed. Kidding aside, we don't hear the ticking inside the car though, and all sounds like "normal".

I will bring the car to Porsche in Bern when we return on Wednesday just to be sure. Still have 9 months Porsche warranty left...

Maybe I can try and record the sound/video and put it up here for reference.

TheBruce

Do you have an exhaust bypass by chance? After I installed a Fister exhaust on mine I would hear a faint ticking in a parking lot with the driver window open and the sound bouncing off a wall or car. I brought it back to FD Motorsports to check out and they said it was normal with a bypass. Its just some back gas in the exhaust.

semicycler

Get yourself a mechanics stethoscope, they're pretty cheap. Then poke around with it until you find the loudest spot. My tandem oil pump on the lower rear passengers side was going and started to make a ticking noise. The replacement was easy. Not saying that's your problem, just that the stethoscope helped located the problem.

Frank996

I have PSE fitted, but seldom use it (only throuh tunnels with windows open ;-)). My partner is telling me nothing is wrong and that I'm just being paranoid.

Thanks for the pointer semicycler as the sound seems to be coming from that side of the car. I notised that the oil temp goes much faster towards the more or less steady 90C (200F) than it did before... Before it didn't reach 90 before 30-45min of normal driving now it took maybe 10 min (level road with no engine pushing). This said, driving through a mountain pass up-hill this morning (Flüelapass - very very recommendable btw) the temp went up to around 110C and I have never seen it that high before. He temperature ent down when we drove down again and stays steady around he 90 or so...

Does this have anything to with the oil pump I wonder? How long would I have "left" on the pump after the first ticking appears (I know this is very loose question), I just want to get home without any breakdowns on the way (about 300km I'd say) ;-)

Oh, the engine temp is fixed at 80C as it should be btw

Macster

Is the oil level good?

Engine noises are hard enough to qualify/diagnose even if one is at the car and can hear the noise.

A "quite loud" ticking noise can be a sign of something serious or the over active imagination of a Porsche owner far from the security of his home and garage.

Not too many months ago my Boxster out of the blue started making a ticking noise. Just prior to the noise appearing the engine was quiet and I pulled into a parking spot and shut off the engine to run a brief errand. Just minutes later when I started the engine I heard the ticking noise. The noise didn't appear to be directly related to a valve lifter, piston, injector but something related to the serpentine belt/accessory drive. I drove the car the couple of blocks to the office, then after an hour or so went back to the car and upon starting the engine heard the noise.

Decided to err on the side of caution and called for a tow truck and then had the car hauled 30 miles to my local dealer. There with the car off the truck and the SM and senior tech present I started the engine and the noise was gone. Long story short after the tech thoroughly checked out the car, the accessory drive and found nothing amiss, after I spent 30 minutes -- this a day or so later -- driving the car around and failing to reproduce the noise -- the diagnosis was something -- piece of paper? -- got in the accessory drive system. The SM/tech told me they "see" this maybe 5 or 6 times a year.

And I was only 30 miles from home.

My advice is try to find some shop where you are that has someone who can listen to the car and offer his/her opinion. In another instance this time in my 996 Turbo I enlisted the help of an owner of an older air-cooled 911 when my 996 Turbo was generating an unfamiliar noise. He didn't think the noise sounded that bad. I was grateful for his opinion but wanted a 2nd one and found a shop in town that had a tech with some Porsche experience. He lifted the car and with the engine running we checked the car out from underneath. No leaks. No signs of any issues but the noise was present. Best way to describe it was a "dry bearing" sound and as best we could tell was coming from somewhere at the back of the car from higher up than lower down. I decided to turn around and head home and several hundred miles later and the next day at the dealer the noise was found to be from a bad idler roller bearing.

Bruce In Philly

My 2009 C2S makes all kinds of scary ticking noises..... I purchased the car with 26K and now it is at 117K... and still ticking. I have noticed that some of the ticks will "turn on" and at times are not there or are less.... it is a bit freaky.

I do believe the engine was quieter when I purchased the car.... but it hasn't blown up and I use about 1 quart of oil per 5K miles. I remember after I acquired the car, my indy started seeing these new 9A1 engines as they were just coming off warranty... he gave me a ring and asked me if my engine ticked ... one of his customers was worried.

Someone here posted they had and '09, and then an '11 (?) and noted the '11 was noticeably quieter than the '09... so maybe Porsche changed a few things.

Like Macster said, take it to a dealer or indy who understands these cars and let them listen. If you are worried, you absolutely should do something about it, but don't be surprised if the dealer tells you it is charm.

Peace
Bruce in Philly

Petza914

Ticking in the .2 cars can be the high pressure fuel pump and it's a normal sound. My DFI Cayenne Turbo S makes this sound.

Ticking in a .1 isn't normal. Could be a bad timing chain tensioner, allowing the chain to slap against the paddle, could be an exhaust leak, could be the skirt of the piston starting to contact the inside of the cylinder wall - could be lots of things. If you think it's a new noise, have it checked out.

With the comment about the Fisters making a tick audible, your PSE system, when in sport mode, is essentially the same as the Fisters. If one of your vacuum valves has gone bad and isn't closing to normal mode when you start the car, maybe you're hearing the ticking that's audible in sport mode. When the car is off, the valves are open (Sport mode). When you start the car, the electrically actuated vacuum solenoid pulls them closed (Normal mode) and this is why the initial bark right when you start the car is louder. If one or both valves aren't being pulled closed that might be why you can better hear a ticking. You can physically see the valves move from under the car.

Wayne Smith

My 2010 C4S 997.2 gets a louder ticking sound each Spring. This is when the sunroof is left tilted open to keep the cabin heat down. It is especially noticeable when I back up against the office building to park.

The .2 cars tick. That being said, there is no way to know if your tick is benign or not. If you aren't sure, have a pro listen to it. Then train your ear for the next time.

Frank996

Thank you all for your replies.

I know its not easy to give advise on sounds, a very subjective sense, but the general consensus seem Its nothing to lay sleepless over.

I discussed this with my non tech spose and she said she could also hear it and we both agreed it didn't have a damaging sound like metal against metal or parts rattling which is a different ballgame alltogether...

Still, I'll drive it nice and easy home on Tuesday and have Porsche Bern to look at it later in the week.

Thanks once again for all of your feedback.

Bruce In Philly

Report back..... I am always interested in what a dealer tells customers especially now these cars are growing in mileage.

Peace
Bruce in Philly

Frank996

Will do good Sir... I'll try and get a time next week with Porsche and revert back in due time.

bazhart

Ticking Noises.

Please note the following refers to the Boxster, 996, Cayman and 997 engines manufactured up to 2009 and not the 9A1 Gen 2 engines manufactured afterwards.

You have asked a question about ticking noises – if you read all this you may well wish you hadn’t bothered because it is a tedious and complex subject that only affects a very small number of engines and may emanate from "something serious" or be a "perfectly normal" feature of the original engine design more noticeable in some examples than others - the potential from which often invites owners to delve into it deeper when in reality it probably isn't worth the time it takes to consider all the possibilities.

There is a ticking noise that can be heard at hot tickover that exists in M96/7 cars with engines that have never been touched from new (are just getting up on mileage) that has puzzled engineers and specialists Worldwide. Many respected specialists have tried numerous solutions only to end up tearing their hair out in frustration that the source of the noises cannot be found or eliminated.
Because it can afflict cars whose engines have never been touched since new, engines that have been rebuilt perfectly and those with nothing wrong with them - but may also be a sign of serious problems – customers can get worked up about a noise when there is actually nothing wrong with their car and to try and eliminate the typical noises - we have tried exhaustively to identify the cause and in the process spent thousands on changing components, road testing and stripping and rebuilding engines for inspection and even designing and manufacturing special parts - and these are our combined conclusions that cover a whole host of potential causes and influences.

The engines are made to tickover at the lowest possible revs from new (even lowering the tickover speed as the oil warms up despite a steady rev counter reading). Anything that is not quite as tight as it was when the car was brand new – can result in the engine slightly hunting between firing strokes and this can cause the timings chains to flap and as a result several completely different components can make a ticking noise. This is a feature of the design and layout of the engine and several of its auxiliary components including the oil pump, chain-tensioner and idle speed control system design and minute wear on parts that are perfectly OK to continue using (like the oil pump, tappets and housings) that all combined together unsettle the tickover and don’t provide enough oil pressure on hot tickover – to damp out.

When an engine ignites the fuel it expands while it pushes down on the piston but as the crankshaft rotates the piston eventually descends down the bore as fast (or eventually faster) than the burning fuel expands – so the actual pressure on the piston varies and is concentrated over a relatively small number of degrees of crankshaft rotation. In addition that force on the piston operates through different angles between the rod and the crankshaft.

As a result of this the crankshafts on all engines speed up and slow down between each firing stroke. This change in speed allows any gears or chains in the system to first drive the camshafts or pumps and then (as the speed slows down) to allow some slack to appear. So if the tickover is slowed down and down far enough - eventually it can be felt as a rock or shake in the engine mountings (or for engines with chain or gear camshaft drives - often in backlash through that drive system) and this makes the chains flap.

As the revs increase there is insufficient time between firing strokes for the speeding up and slowing down of the crankshaft to move as far (or be of as great an amplitude) before the next firing stroke arrives - smoothing the result. You might imagine this rather like a single cylinder or multi cylinder engine because as the tickover revs reduce the engine becomes more like a single than a multi. If you could record the speed that the crankshaft is rotating at – not in revs/minute but taking several readings during each crankshaft rotation – you would find that the speed is not actually constant but is continually speeding up and slowing down a little bit during each crankshaft rotation.

Those used to rebuilding or tuning older engines designs will be used to adjusting the tickover screw to find a smooth tickover speed and will know that it takes very few revs to change a bad ****** or tick into a perfectly smooth and quiet engine - but modern ECU systems rarely provide this type of adjustment. Instead they measure the tickover speed and compare it to a pre-set target speed programmed into the ECU and make frequent adjustments to try and keep the revs where the programmer originally intended them to be.

This can create a difficult scenario because instead of allowing the engine to find a natural tickover speed (by adjusting the throttle tickover screw) it can continually be making adjustments to try and make the engine return to the speed the ECU was programmed at – even if other settings are in an unsuitable position – and this can result in hunting in which throttle or ignition changes go up and down continually each time the ECU reads a tickover speed at variance to the pre-set speed - to try and find a steady tickover speed and this in turn makes any flap in the chains worse (and often cyclic).

If that change was too much or too little the ECU can only find out when the next speed measurement is taken after another full revolution and three firing strokes - and is then forced to adjust it if it is still not right. Although the systems are damped electronically it is a more difficult situation to find a nice smooth tickover compared to the older tickover screw method. You could perhaps imagine the affect being rather like a traditional engine in which the tickover is controlled by a bye-pass screw that you are controlling with a screw driver and every time the engine makes a revolution a red light comes on to inform you it is a little too slow (so you turn the tickover screw to open the byepass hole) but the next time the engine makes the next revolution a green light comes on to inform you it is now too fast and you turn the bye-pass screw in the other direction. Each time you do this the engine speeds up or slows down more than you want and you end up turning the screw one way and the other in jerks trying to find the right setting that smoothes the tickover at the right speed. It is easy to see how this could result in ****** in the chain camshaft drive system that would have been avoided if the bye-pass screw had been left in one position.

As a result those rebuilding completely different manufacturers engines often experience tickover instability because some of the engine is now like new (or even modified and potentially better than new) while other parts may be worn with age so while the rebuilt engine has strong tickover power pulses again – some of the other older components are not working exactly as they used to (of which the throttle penny that opens and closes the throttle is typical as it wears as a result of air simply passing across it and after some years doesn’t seal in the same way or open at the same rate as a new one so the tickover byepass adjuster has to work with a different bleed rate past the throttle penny).

Standard Lokasil bore engines distort the cylinders oval with time and this results in a less strong tickover pulse (that helps reduce the magnitude of fluctuations) but a rebuilt engine with tighter piston clearances may well result in a stronger tickover pulse than the engine was programmed to deal with. So sometimes after a rebuild an even stronger tickover firing impulse results (because the engine has been rebuilt well) but have older, slightly worn and less balanced auxiliaries.

This can push the original tickover control feedback parameters beyond what the designers originally expected or tested for - resulting in a slight tickover noise that they cannot get rid of because they don't have the means to raise the tickover slightly (which Internet research will confirm).

A whole new Porsche engine may well not exhibit these noises (as everything is brand new and tight
With emphasis on low emissions - manufacturers try to set the slowest tickover speed and least fuel delivery they can possibly get away with for their particular engine on tickover - and with modern ECU digital controls often arrange the tickover control revs to fall lower and lower in steps as the engine heats up – and the oil temperature and viscosity changes – and make adjustments for the air conditioning being switched on etc (adjustments that M96 and M97 engines incorporate with 10 different programmes inside the ECU that react to different conditions and temperatures all pre-set to run at the lowest tickover that will avoid shakes and noises when the engine was new).

Engines where the layout creates poor balance issues need heavier flywheels to damp out cyclic vibrations but a flat 6 cylinder engine has good natural dynamic balance and can as a result get away with lighter flywheels and engines with cylinders not all in a straight line can also result in lighter crankshafts.

Sports camshafts make it necessary to increase the revs for a smooth tickover but Camshafts systems that provide variable timing and/or lift help run both sports cams and better breathing at low revs and can enable manufacturers to lower tickover revs further (as in the M96/7 range). However engines with variable camshaft timing and lift produce better torque at low revs (as a result) and this means ironically that the strength of the individual power pulses can be stronger than they used to be on tickover and therefore the adjustments made during each crankshaft rotation need to be very small indeed to avoid creating this over-compensation and add an additional feature making it more difficult for the pre-programmed tickover systems to try and react to.

A flat 6 layout like the 911 also provides one of the best natural dynamic balances enabling it to be run with very light crankshafts and flywheels (contributing to acceleration) and as it also features chain camshaft drives and variable camshaft timing and/or lift - is probably more prone to this problem than almost any other design layout (and the effect of chains in particular - flapping under dynamic loads can be seen by viewing the Roll-Ring Chain Tensioner videos on You Tube). www.youtube.com/watch?v=-qhVOW--QSs. You will probably not appreciate the forces involved without viewing that very useful video clip.

With almost everything against it - this engine range are set for such a low tickover within the ECU when hot that anything that alters the balance of the performance from one cylinder to another – (even if it is improved) can introduce a "******" in that smooth running between firing positions that the system simply cannot smooth out. It has been noted that whenever this “tick” appears (whatever the actual cause and with different causes) it is almost always on bank 2 near the rear (cylinder 4) in the camshaft drive chain housing (and this is significant).

The ECU reads the tickover speed round about when cylinder 2 or 5 has fired. If either is too fast or too slow it tries to do something about it by adjusting the throttle or bye-pass opening.
With a firing sequence of 1 6 2 4 3 5, the next cylinder to fire after cylinder 2 is cylinder 4 – so if the crankshaft speed at cylinder 2 is read as too slow the ECU will open the air flow for firing cylinder 4 – speeding it up and this will result in a ****** because the camshaft drive to bank 2 (and cylinder 4) is at the end of the intermediate shaft and additional chain on the RHS rear of the engine (unlike bank 1 in which the camshaft sprocket driving bank 1 camshafts is adjacent to the IMS drive chain driving it).

Even used engines that are rebuilt with new parts usually rotate more freely (with less resistance) than a new engine and often this means that the pre-programmed tickover system simply tries to run the engine too slow to remove a ticking noise from the chain ****** at tickover at the bank 2 camshaft chain drive position.

The IMS and camshaft chain hydraulic tensioners are at best a poor design. They do not feature a spring loaded ball valve (to prevent the oil from returning into the system at low revs when the oil pressure is lower and the chain is trying to flap) but instead rely on the movement of the hydraulic piston and oil to try and push the ball valve closed. In bank 1 this ball sits on the seat and gravity helps close it unless there is sufficient oil pressure to move it away from the seat (and as a result whenever the bank 1 tensioner is removed from an engine it is still difficult to squeeze closed due to the retained oil inside).

However - bank 2 tensioner fits the other way up and the ball in this side therefore sits away from its closing seat and can only close if the oil can physically move it vertically to close. It doesn’t work well (especially when the oil is hot and thin) and whenever a bank 2 tensioner is stripped there is no oil inside it and it is easy to squeeze shut. As a result it is not as efficient as the same design of tensioner in bank1 (because it is upside down) and this is also a contributory factor in why the noises tend to emanate from bank 2.

So the typical scenario is when the ECU tries to speed up the engine after reading speed at cylinder 2 firing and the speeding up works from the IMS twisting it faster as the acceleration is transferred to the other end of the shaft and camshaft chain at the side of the engine where the tensioner is inefficient and allows a larger ****** to occur than in the same scenario after the tickover speed is read around cylinder 5 has fired (as the next cylinder to fire is cylinder 1 on bank 1 where the hydraulic tensioner works best).

It all basically means that if you continually slowed down the tickover the first place you would expect to create a problem would be heard as a tick on the bank 2 rear of the engine.

Modern engines (like these) suffer more because as the oil pressure and flow reduce at hot tickover it is also supplying variable camshaft timing solenoids, hydraulic tappets (twice as many with 4 valve heads) etc increasing demand and resulting in localised pressure drops at tickover where a lot of oil feeds deliver to various other components (as they do in the cylinder heads where the oil gallery to the bank 2 hydraluic tensioner comes after it feeds all the tappets, camshaft solenoids and finally feeds the bank 2 chain tensioner). It is notable that the Gen 2 engines have a much improved oil pump with better control delivery to critical components.

Because this potential to ticking is exacerbated in these engines we redesigned the hydraulic chain tensioners creating several modified versions to fit a spring loaded ball valve – to try and maintain better pressure (which sometimes worked and sometimes didn’t) the problem being the lack of space to include a hydraulic buffer reservoir filled with oil when the engine was running at higher oil pressures - to maintain that high oil pressure on the tensioner piston as revs fall (as used successfully in air cooled Porsches for many years) and the tensioner leaking too much oil from low pressure at tickover as a result of “cheaper” design. The tensioner blade is so long that we think that when the chain is snatching it manages to push the oil back into the feed gallery ay tickover sometimes faster than it can refill to damp out the next fluctuation.

If the noise is caused by this upset balance then it is not mechanically serious, is just irritating and usually goes away if the revs are raised a little - or the inertia/load on the engine is increased (but not usually if it is caused by something that needs serious attention).
Increasing the load on the engine at tickover is a way to test the seriousness of the cause. Because the ECU alters the parameters to keep the tickover the right revs for the temperature pre-set - any extra load has to be matched by an increase in air flow to the engine and consequently the fuelling - and it also increases the effective weight or inertia of the rotating mass that also reduces the range and size of impulses between firing stokes. As a result, loading the drive (tiptronic gear engagement increases drive train inertia) or switching on the air-con (increases loads through the air-con pump and alternator discharge feeding the additional fans that come on AND switches to a different map in the ECU – raising the tickover speed slightly) can force the ECU to open the throttle or bye pass more and in turn deliver more fuel - so if the imbalance was derived from any of those systems - an increase can smooth it out due to the error becoming less proportionally to the increased airflow.

Increasing the revs slightly also raises the oil pressure feeding the hydraulic chain tensioners improving the efficiency of the poorer bank 2 hydraulic tensioner.

Because the above results from basic design issues and parameters – even a perfectly normal standard engine can start to “tick” if left to tickover long enough because the coolant flow is minimal and the oil temperature that signals the ECU to alter the tickover revs – fluctuates (and as they age often immediately tickover speeds are reached) more often coming and going as the ECU varies the desired tickover revs with different feedback readings for temperatures, pressures and delta speed) and these are not always noticed on the revs counter.

Any other mechanical problem can also contribute to a greater tickover speed variation between cylinders and induce the same noise.

POTENTIALLY SERIOUS CAUSES, that can upset this balance include, scored bores, cracked cylinders, worn or damaged tappets, worn chains, reduced oil pressure (through worn crankshaft shells etc), lose valve seats, air leaks, air mass sensor faults, etc. So anything that unbalances the firing impulses between individual cylinders at tickover will make the engine more likely to tickover with a ticking noise.

Symptoms for most causes are the same - a ticking noise like a tappet with too much clearance - although a scored bore can also result in the piston tapping harder at the cylinder head and crankshaft shell wear can be heard as a knocking that continues as revs rise.

INNOCENT CAUSES include, carbon deposits, lose exhaust connections,, non standard exhausts, worn hydraulic chain tensioners, worn throttle pennies, blocked tickover byepass valves, worn fuel injectors, worn or loose spark plugs, etc - in other words - things that just happen to be slightly less perfect than when the car was new and just requiring a slight increase in tickover revs to eliminate (which is not normally adjustable).

Innocent ticking noises on tickover have no implications for long term reliability but are frankly just irritating!

Because there can be a lot of different minor variations in a wide range of components and settings that each destabilise tickover - these special parts can help if that was the only cause - but if not it makes no difference and sometimes it can be a combination of several other unconnected things that results in the ticking noises and chain slap.

For example - when a piston badly scores it can often result in a tapping noise - heard mainly when the customer is out of the car to investigate and it is running at tickover. So once the engine has been properly rebuilt the customer does not expect to hear a similar noise (that he is convinced is the same one) but may not be caused by anything serious - just a slight imbalance somewhere in the tickover, fuel, compression, ignition, induction or exhaust system due to old age.

Often the nose was present before the engine was rebuilt and yet if it comes in as a non-runner the repairer cannot determine this and sometimes the consequence leads to the customer questioning the amount and/or quality of work carried out (which may be faultless).

OTHER SERIOUS CAUSES OF NOISES ARE

(1) Crankshaft bearing failure – big ends or main bearings (or both) – usually caused by wear on the rear main bearings lowering the oil pressure just there and consequently therefore lowering it to the number 6 or 3 big-end (because the oil flow path travels to the main bearing first and from that up into the crank pin/big end area).

The noise from this sounds quite heavy and increases with revs and is present as the revs rise or fall – usually louder if the engine is hot.

This failure of the main bearing white metal in the shell is caused by crankshaft bending or flexing increasing the wear loads on the shell due to the large overhang at the rear of the engine to accommodate the two chains being driven there for the camshaft system. If the engine is being used for aggressive braking or is over revved - this can bend the flywheel end of the crankshaft so much the starter ring can touch the bell housing inside. The dual mass flywheel is a contributory factor as it is so heavy and relatively poorly balanced as it wears. For most racing applications in other cars with similar dual mass flywheels – they are removed to reduce the weight and improve balance and replaced with lighter solid flywheels but these have less of a natural damping affect and can make things sound worse.

(2) A fuel injector can also make a tapping sound that varies with throttle opening (and consequently with revs) but usually if you rev the engine and then shut the throttle – it would not make the sound as the revs fall because there is no fuel passing into the engine (the injector pulse is switched off).

(3) A hydraulic tappet is the usual diagnosis for a slower noise than at crankshaft speed – more of a ticking noise. It often goes away after the engine has warmed up (as the hydraulics pump up the tappet) but can also be caused by the top of the tappet actually wearing away (or even creating a hole through the top) in which case it is permanent. Wear in the tappet housing can also reduce the pumping efficiency of the oil transfer from the oil delivery system into the tappet.

(4) The Cayman S 3.4, 996 3.6 & 997 3.6 &3.8 engines can have damaged pistons and scored bores – usually after about 50 to 70K miles. The damage is like seize marks on one side of the piston (the reasons and causes of which we understand and can remedy during a rebuild) but the extra piston clearance that results allows the piston to tilt as it goes over top dead centre and the edge of the piston just touches the cylinder head making a tapping noise. This can be checked for by putting a camera (often called a bore scope or boroscope) to look inside each cylinder. The damage usually seen on bank 2 (cylinders 4, 5 & 6) on one, two or all three bores (because on this side of the engine the thrust load of the piston is on the hotter part of the bore whereas on bank 1 the thrust side is the coolest) . The damage seems to take some time to gradually get worse and initially can be present with no symptoms at all – gradually increasing oil consumption and slightly less sharp performance (that many owners do not notice until they receive a rebuilt engine back and remember how crisp it used to be).

(5) Valve seats. It is not unknown for a valve seat to become lose in the cylinder head and bend or break a valve – early signs would probably be an intermittent tapping noise.

(6) A worn IMS bearing (or a worn or damaged chain) or swarf trapped in the scavenge recirculation pumps, or damage to the chain sprockets, or wear on the chain slippers, or worn hydraulic tensioners – can all throw up a ****** in the engine system as it revolves which can emanate as a tick.

(7) You will probably be sceptical when I tell you that the exhaust manifold leak can also make a noise exactly like a metallic tick (but believe me it can and I won the bet to prove it!).

The bolts that hold the manifold to the cylinder head rust and the manifold becomes slack. The gasket is a thin metallic one with small ridges to seal against the surfaces, but it doesn’t fit too well leaving a very thin sealing face between the exhaust port and the exhaust gas recirculation (EGR) ports. All heads have the grooves for these ports cast in and some are drilled through to inside the exhaust ports while others are not – and some have an EGR system on the car while others do not.

The ports connect all three cylinders on one bank together. When the slack bolts and thin contact result in a gap appearing between the exhaust port and the EGR ports, at tickover – the cycling of the pulses makes a very metallic sounding noise that goes away as the engine falls in revs but is there as it increases from low to medium revs (very like a tappet getting quieter as the revs and oil pressure rise – but tappets would still be noisy as the revs fell – but not the exhaust system as the throttle will be closed and the exhaust pulse of little or no intensity).

(8) We have even come across spark plugs in which the centre core has become loose from the outer threaded housing allowing a leak path introducing a tick.

(9) Early engines have 5 chains and later ones have 3 – and as the chains wear and the sprockets wear (together with the rest of the engine) eventually there is enough slack to allow the ****** to sound like a tapping noise (as the reversal of the crankshaft speed pulls the chains tighter on one side and then the other against the tensioner which at tickover has relatively low oil pressure and tension).

But it is not always simple to analyse the noises.
The sound always seems to come from cylinder 4 area (but this is where the chain driving bank two camshaft sits).

The firing sequence is 1 6 2 4 3 5 and looking from the top from the rear towards the front (of a 911) on the LHS are cylinders 1, 2 and 3 and on the RHS 4, 5, and 6.

This means that usually a cylinder fires one close to it in the next sequence. Cylinder 6 next fires cylinder 2 (next opposite), 2 to 4 is the same, 4 to 3 is at opposite ends of the crankshaft but 3 to 5 is again next door to one another opposite as is 5 to 1, but then 1 to 6 is at opposite ends of the crankshaft again.

This means there are two phases in which the loads are transferred from one end of the crankshaft to the other – one transferring drive from bank 2 (cyl 4) to bank 1 (cyl 3) and one transferring it from bank 1 (cyl 1) to bank 2 (cyl 6).

When this first reverse happens (firing from cyl 4 to 3) the cylinder 3 is at the end of the engine where the crankshaft drives 2 chains (and the intermediate shaft is not required to do anything) as it drives bank 1 camshaft directly and so there is plenty of oil splash from the chains onto the bank 1 camshaft chain drive and no IMS shaft twist to consider. But in comparison when the drive changes from cyl 1 to cyl 6 (at the other extreme end of the crankshaft) the intermediate shaft also has to transfer the bank 2 camshaft drive to the other end of the engine and then up through only one chain (less lubricated than the two bank 1 chains). This means that specifically – the cylinder firing order from bank 1 to 6 would potentially create the greatest theoretical twist/****** of all the other cylinders onto the least lubricated chain that is running right next to cylinder 4 (bank 2) where the noise usually comes from.

It seems possible then that as all the engine components gradually wear and all the parts that contribute towards the mass of the system get looser – that this ****** creates a noise – only at the lowest of engine revs and that this goes away when the torque converter is engaged by selecting “D” or “R” - or engaging the air-con (because this alters and increases the mass and damping effect of the crankshaft – just as if it had suddenly become heavier and selects a different tickover map).

We have also heard similar noises from a slightly worn dual mass flywheel.

In fact similar noises have been heard for years in 3.2 911’s from the gearbox at low revs (although those with the hydraulic air cooled 911 tensioner system - that is far more sophisticated than the M96.97 one do not usually exhibit chain ****** noises) and from racing 944’s and 968’s (with lighter flywheels - although their ribbed belt camshaft drive minimises it) and from many other racing cars with lighter crankshafts.

It is also a very common phenomenon with other higher performance sports car engines with light flywheels after an engine rebuild. A cure is often just to turn up the tickover revs slightly and the noise usually goes away (giving credence to the conclusions it is simply caused by a slightly uneven tickover and chain ****** which is slowly creeping up on older engines at tickover) – it has no detrimental effect and it is pointless wasting huge amounts of money trying to get rid of it and you would have to replace lots of parts that are working perfectly OK with new ones for no reason other than a slightly stiffer fit or movement to quieten a noise only present on tickover that is otherwise doing no harm.

But unfortunately you do not have an adjusting screw to change the tickover revs on these cars. It can be done from within the ECU where there is a range different maps of tickover revs that reduce tickover speed as the engine temperature gets hotter (which also fits in with our experiences). Unfortunately the lower the tickover the lower the oil pressure that feeds the poorly designed hydraulic tensioners and the less resistance there is to the engine inertia loads.

It does not seem to cause too many problems with "untouched engines from new " (as people get used to it and assume it is general wear and tear) but concerns about bore scoring and the different noise that are not only at tickover caused by bore scoring has made many owners need the problem to be properly investigated. But although some noises are caused by serious issues and need investigating - there are an increasing number of owners hearing this type of noise that I am describing (and others are confirming) that seem to have no connection with an actual mechanical fault (except gradual wear of components that still work OK) and it is worrying them unnecessarily. Various recordings have been posted on the internet to try and identify the causes (which is impossible in most cases)

We know from past experience (and developing our 3 litre 944 turbo) that light flywheels and different flywheel weights and damping can create some noises at low revs and also that many racing engines - the 996/997 turbo - GT3's etc all have similar noises and some of them may well not indicate a serious problem – so stop automatically worrying unnecessarily if you hear a similar noise - at least until it is investigated or there are other contributory factors (like increased oil consumption etc).

There was (for example) a thread on Boxa.net where a main agent has tried and failed to stop the noise (like we similarly tried) and is got a lot of criticism - whereas - they deserve some credit for trying the obvious things (like we did) and will probably come to the same conclusion.

Many believe it is Piston slap (which is usually more evident from cold) and it is a fact that when an engine is hot and ticking over the coolant flow to the cylinder block is so slow it remains hot while the pistons shrink back a little as they are hardly burning any fuel and this can increase the piston to cylinder bore clearances. But the noise is usually still only be heard near the bank 2 cam chain area – so we think this is unlikely to be the cause.

Our conclusion to all this expensive research and work is that the engines are prone to unsettled tickover impulses and have relatively light flywheels and crankshafts and are set to tick over so slowly when hot that this can set up a cyclic chain ****** caused by larger than normal variations in tickover firing impulses and the layout of the engine that creates a metallic tapping sound.

Anything that increases the inertia or load on the engine (even at the same revs) can eliminate it.

Sometimes fitting a plastic tensioner end cap on a tensioner piston or a Hartech development hydraulic tensioner (with sprung ball valve) can eliminate it, sometimes speeding up the tickover will remove it - all pointing to the tickover speed variations being the route cause – but the cost of trying these different solutions compared to the infrequency that it makes any difference makes such a prospect uneconomic.

The next question would be what would cause such an uneven tickover between firing impulses?
It can also be caused by a really good rebuild - especially if only one or two cylinders have been replaced with Hartech Nikasil Alloy cylinders and the others have been left as Lokasil - as the Nikasil cylinders will produce better compression and are often fitted to bank 2 (where there is a bigger variation in drive train flex than many of the other cylinders.

A contributory factor relates to the way chains work and wear - as well.

A roller chain approaches the sprocket and the roller slides into position as it connects with the sprocket – but as the sprocket wears the diameter of the root of the tooth profile reduces and with it the chordal distance between the teeth reduces – while at the same time the distance between the chain rollers does the opposite and increases (as a result of chain wear and stretch) and this allows the next roller coming into contact with the sprocket to touch on the tip of the tooth and slide down into the bedded contact area – exacerbating wear and creating noises.

In Porsche history this was the main cause of the 944 S. S2 and 968 camshaft chain failures as the hard but brittle chill cast camshaft sprockets metal fatigued due to the forces on the tips of the sprockets (as they and the chain were wearing) eventually snapping off a tooth.

Towards the end of production Porsche cleverly altered the shape of the tooth from standard - so it was more pointed and thinner at the tip and this resulted in the incoming roller from the stretched chain not impinging directly on the tip as it slid down into position and as a result reduced the tip loading and prolonged the life of the camshaft sprockets.

The M96 engines initially were built with roller chain drives from the crankshaft to the intermediate shaft and then from there to the camshafts. Inevitably as they wear – this phenomenon of the worn chain and sprocket existed.

Later cars were fitted with HiVo chains between the crankshaft and the intermediate shaft (regarded as the “silent chain”) but few explanations account for why.

Close inspection reveals that as the HIVO link approaches the sprocket the curve of the chain as it rolls around the sprocket actually changes the shape of the incoming tooth contact angle – so that it gradually sits against the tooth rather than slides down into it (as it does with a roller chain) and furthermore as the sprocket wears (and the HiVo chain runs around a smaller diameter) the smaller diameter that the chain rolls round rotates the chain teeth more and actually closes up the contact gap – becoming almost a self adjusting tooth fit automatically adjusting for chain and sprocket wear – and hence they tend to run quieter for longer.

It is interesting that in our experience the most likely engines to run with this annoying ticking noise on tickover are the older roller chain type and not the newer HiVo type and as crankshafts are very expensive to replace – it seems that in some cases it is the classic roller chain sprocket wear problem that may contribute to the ticking noises.

HiVo chains are also much less prone to flapping than roller chains (having a reported self damping affect) and so it seems that among many contributory factors the actual chain design of the earlier engines could also be yet another contributory factor.

Piston Pin (or gudgeon pin) off-set.

We have purposely left this last technical issue until the end as it must be considered along with all the other issues raised before as yet another one that doesn’t help matters – because - finally there is one more very odd contributory factor. It has been know for many years that piston slap can be reduced by positioning the gudgeon pin slightly offset to the centre of the piston towards the thrust side – as this allows the con-rod to pass slightly over the straight in line position more quickly after TDC and avoids the piston slapping under the combustion pressure as the crankshaft and piston go over TDC.

The pistons fitted to these engines all have a piston pin offset so it would be reasonable to assume that this was designed in to achieve this long standing technical and proven benefit of more quietness.

However – by some slightly odd design anomaly – the pistons on some engines are fitted the “right way around for quietness” on one side of the engine but entirely the opposite way around on the other side.

If the piston crown is symmetrical around the gudgeon pin axis then it can be fitted either way around and the valve cut-outs in the crown will still miss hitting the valves. But conversely – if the piston crown is asymmetrical then it can only be fitted one way or the smaller relief to miss the smaller exhaust valves would be where the larger inlet valves protrude and would interfere with them.

The Boxster models and the 996 3.4 all have asymmetrical piston crowns and when they are transferred from bank 1 to bank 2 they must be rotated around a vertical axis so the smaller exhaust valve pockets in the piston crown remain at the bottom of the engine (as the exhaust valves are always facing downwards). They also have a relatively large pin offset around 0.9mm.

The Cayman S, 3.6 and 3.8 engines have symmetrical piston crowns so they have been marked with an arrow to enable assembly to place the off-set the right way round for both bank 1 and bank 2 and have smaller offsets as well around 0.5mm.

This means that IF this offset is a contributory factor it should be more of a problem in the Boxster and 996 3.4 engines than the Cayman S, 3.6 and 3.8 engines.

In our experience this is in fact the case with Boxster S engines very rarely making the ticking noise on tickover (we assume because the smaller bore results in a less strong tickover pulse) – 996 3.4’s being the most likely (although still rare) and the other models almost never making the noise – so in that way this explanation does fit.

When the Gen 2 engines were designed Porsche returned more to the design for the piston crown of the air cooled 911’s which is asymmetrical and therefore once again built engines with one bank correct (for this theory) and the other incorrect (and quite a large offset around 0.75mm) – but then these engines have a far more sophisticated oil pump able to manage the chain tensioner pressures much better on hot tickover and have different bore to stroke ratios and tighter piston fits (that always help reduce piston slap noises) due to the change to Alusil cylinder bores.

The only odd issue though is that – at first glance - the noises emanate from the bank 2 side in which the offset is the right way round and not from bank 1 where they are theoretically incorrect – that is until you research the whole issue further and discover that the piston slap noises designers are trying to reduce are not at tickover but at low speed powered running speeds (as there are no thrust pressures or loads to speak of on tickover) and this is a rev range in which these engine produce exceptional torque and therefore thrust pressures.

You also discover that setting the gudgeon pin offset towards the thrust face reduces the acceleration over TDC that reduces the slap of the piston from one side being compressed as it rises to the other side of the stroke where it is pushing down with thrust – (and this is the basis on which these off set pistons were introduced). However the down side is that at BDC the acceleration is actually increased and therefore this could make the bank 2 side cause the noises but at BDC instead of TDC.

Now as the stroke of the engine range has been increased from the original 2.5 Boxster to the 2.7 to 3.4 engines and finally to the 3.6 and 3.8 engines the height of the cylinder block has remained the same and this means that the pistons move further down the cylinder bores than the first 2.5 Boxster engines. However the length of the cylinders has remained the same – which means that the later the engine the more of the piston sticks out of the bottom of the cylinders at BDC. As pistons are tapered towards the top – this means that as the piston falls out of the bottom of the cylinder – the diameter of the piston that remains inside is smaller and the piston clearances are momentarily increased and therefore likely to promote piston slap.

Because the flywheel sensor that informs the ECU if it should pick up the revs or slow them down – is just before the cylinder fires that is in the position that we always hear the noises emanate from – it seems possible that a sudden acceleration at this point in the crankshaft rotation, on that side of the engine where the piston acceleration at BDC is highest and the cam-chain tensioner we know to be less effective – when the oil pressure is low (on hot tickover) can all contribute to the noises we sometimes hear.

Unfortunately after already spending hundreds of hours and thousands of pounds a variety of potential solutions for solving this occasional problem and with no detrimental consequences (apart from a slightly irritating noise that anyway is also often present in original engines as they age) and with some many potential influencing possibilities that are part of the basic original design that we can do nothing about - we have to accept that some engines (mainly 3.4 996’s) may – after a rebuild – exhibit this slight tick on hot tickover – that neither we (nor the many talented and highly regarded specialists around the World who have also tried to identify and find a solution to and failed) can eliminate.

Ironically – after all the work that we put into understanding this problem I concluded that maybe we call it “TICKOVER” precisely because it is the speed at which the engine will stop ticking – and that I wish I had just accepted this before embarking on a whole lot of time and money trying to solve a problem that simply has too many potential causes emanating from the original design parameters – to solve.

Baz (technical director Hartech Automotive)

19VFB19

^^^
True dat!