ninerguru

I have been chasing this engine noise for the last month or so but has been taking place since last fall... Things I've done: new water pump as it shaft had some play, replaced bearings in alternator, replaced belt adjuster idler as it sounded funny while holding a screwdriver to my ear to listen in. The other two idler rollers sounded fine. Changed the belt as a precaution...

Here's the video:

The noise can be heard at around 7 seconds into the video, at about 13 secs, the air pump shuts off. The sounds is from something that turns with the engine as can be heard to stop abruptly when the engine shuts off (2:18)

The only thing left is the power steering pump. Has anyone have one of those fail? Car is a 2004 with 46K miles...

Any help would be appreciated... Thanks!

v12man

Noisy timing chain? I have had a tensioner go soft (but not fail completely) and we replaced both tensioners - motor quietened down a lot after replacement.

Permafrost

I can't tell if this is the same sound my old 996 GT3 had, but my car had a variocam actuator go bad. To diagnose that, we got the car up on a lift, and then used a stethoscope on the timing chain covers. There was a perceptible difference between the two sides. There is a seal on the actuator (which is the gear at the top of the timing chain) that is held in place by a small plastic retaining clip. That clip broke, allowing the seal to blow out, which in turn made the actuator "pop" every second or so.

Macster

The power steering pump is not the only thing left. But a problem with the power steering pump at least in some models -- I do not know if the 996 GT2/GT3 can manifest this problem -- is a pressure relief valve in the power steering line fails and high (too high) power steering fluid pressure is directed to the steering rack. This forces fluid past the seals but this fluid can be held for a while by the rack's dust covers.

In the meantime the power steering fluid level drops and the pump gets noisy and if not caught in time not only does the power steering lines have to be replaced, along with the rack, but the power steering pump having run low on fluid is shot too.

Generally the power steering pump noise prompts the owner to bring the car in but this it is often too late to save the power steering pump.

With the above out of the way, my initial impression is the noise is an exhaust leak.

But it may arise from an accessory drive or even a roller idler bearing.

Since the noise appears shortly after engine start and a cold engine start you can remove the serpentine belt -- note the routing and direction for rotation for putting the belt back on again -- and start the engine and thus at least know if the noise was coming from the accessory drive system or of course if the noise is still present then it is coming from 'inside' the engine.

With the belt back on again you need to pinpoint where the noise is coming from. Where it is coming from helps identify the source/cause of the noise.

(You can even start a hot engine without a belt but you can't run it long. Just a moment or two -- to be safe -- but if the noise is sure to be present upon startup all it takes is enough to run time to confirm the noise is present or not.)

I take it there is no CEL, no pending error codes?

Have you had the engine hooked up to a PIWIS2 diagnostic computer to ensure all vital signs -- mainly I'm thinking of camshaft timing -- are ok, stable?

The problem can be the engine is not run long enough for the DME to flag an error but the error exists nonetheless and a trained tech viewing realtime data from teh engine and its various sensors can make a diagnosis without there being an error code.

The oil filter housing oil and the filter element do not show any scary bits of material (metal) or an excess of non-metallic debris?

Really you need to get the car in the air and the engine running and the noise present and using a mechanic's stethescope pinpoint as close as possible from where the noise is coming from.

Once you know this you or a professional can make a better guess as to what is going on.

Sincerely,

Macster.

ninerguru

Macster, thanks for your reply.

Don't know about an exhaust leak... If you listen to the last 2 sec of video, sounds like something rotational stops suddenly...

There is a TSB for cars affected with the PS issue, Turbos I believe and noise should go away when pressing clutch. GT3s are not affected... PS fluid is withing range.

No CEL, car has been running with a noise since last Fall, originally told by trusted tech it sounded like a belt roller. Car has seen about a dozen track days since beginning of year. Runs strong and has no other issues...

Oil was changed at beginning of season, nothing extraordinary showing in filter...

Might have to have it connected to diag system...

I will try removing the belt with cold/hot engine once temps come down here in NJ as it is like 100 Deg today...

Thanks again for your feedback! Lou

Macster

I didn't listen all the way through the clip. I'll give it a full listen after I post this.

The power steering issue I mentioned is not related to the boosted clutch of the Turbo.

The power steering issue is based on what I was told -- or at least understood -- is common across the model lines. The symptom is not a high pitched whine/squeal that comes from a vibrating valve but from a power steering pump that is low on fluid because a high pressure relief valve that fails and allows too high of pressure fluid to be routed to the rack. The rack's seals can't hold this fluid inside and it leaks out past the seals. The seals are themselves 'sealed' against dust by rubber boots which can for a while hold this fluid. They get soft like weird breast implants.

In the meantime though the pump is low on fluid and this leads to damage and noise, or noise and damage.

However, you report the fluid levels are ok and that eliminates the power steering pressure relief valve.

Can't imagine a belt idler roller bearing holding up for this long making that racket and given the amount and type of driving you have done.

In fact I can't imagine anything emitting that level of racket holding up that long, that is anything critical.

You sure something's not rubbing against an accessory drive pulley or the crank pulley?

Sincerely,

Macster.

Macster

Well, I listened all the way through and the last 2 seconds or so sounds like I would expect an engine being shut off to sound. Since the engine is off the fuel and spark aren't being triggered and in this case if the noise was arising from pressure of combustion or exhaust I would expect the noise to cease a moment before the engine stopped rotating.

Let me listen again but tomorrow when I'm fresh.

Sincerely,

Macster.

maximtaylor

Check you dont have a loose spark plug on the left bank, this can make a similar woo woo woo woo noise.

ninerguru

OK, had an opportunity to remove the belt and run the engine without any accessories. Noise still there... It seems to come from the timing chain cover area. If I put my hand on it, I seem to feel it.

Now, looking at some build pictures of the 4.0l engine posted in the past, it seems that the chain tensioners are oil feed as there seems to be a duct on the chain body coming from the block and the tensioner cover seems to have some oil ducting. Can anyone confirm?

Finally, it seems that the driver side tensioner might be accessible by removing a couple of water hoses after the system is drained. Looks like the alternator would have to come out also. Just two bolts hod it together.

Any concerns regarding upsetting the timing once the tensioner is removed? Looking at engine manual, looks like tensioner pushes on chain guide.

Comments? V12man, Do you recall if work was done with engine in place? Thanks!

v12man

Work was done with the engine out, but I think you could change them without removing the engine, (if the timing slips you are in trouble and the motor would have to come out) but this is not advisable, as you should check the condition of the chain ramps as well - these apparently do crack and break as they are made of plastic.

Put a stethoscope on the cam chain covers - you will clearly hear it if it is a cam chain making a noise - alternately ask someone who works on air cooled porsche motors to listen - they know what they sound like when they fail.

christallon

Did this ever get resolved? Unfortunately the video is unavailable. Curious about what you experienced and what the sound ended up being.

Thanks
Chris

Macster

Why do you ask?

Unfortunately I was unable to come back to this thread due to family medical problems and dealing with my elderly parents. I tried to listen to the clip again but it is no longer available as you corrected noted.

christallon

I am asking because I have a pronounced knocking noise coming from the right front area of the motor that does not start making the noise for 4-5 minutes from dead cold. I took the car to a local Indie shop nearby. The mechanic put it up on a lift and started the car. The noise appears 4-5 mins after cold start up as the temp rises toward 180 deg then stops after the car is super warm, maybe 5 minutes after noise appears. The noise is evident at idle to about 1400 RPM's then goes away, and also goes away completely when the car is hot, even at idle. It does not cause any running problems, and does not cause any CEL events. The mechanic thinks we should change out the right side tensioner first to see if that does the trick. The mechanic used a stethoscope and felt the noise was coming from the right side cam chain box. Any thoughts or guidance would be very much appreciated.

Macster

Well, I think you ought to listen to your mechanic's advise. I like the fact a stethoscope was used to pinpoint the source of the noise. Not many things that can make noise in that chain box.

christallon

I just had the right side chain tensioner replaced and it sure looks like the knocking sound is gone Very happy. I will check progress over the next week or so to be certain, but I think this repair did the trick. The motor actually sounds quieter overall.

The cool thing about the 6-3 is that there is an access cover under each tensioner so you can get to the tensioners without having to drop the motor. Easy Peasy. I probably could have handled the repair myself, now that I understand the design. Will report back in a week or so with further observations.

It's a 964 part number and is made by INA in Germany, OEM stuff.