apw964

Ok, so it's been a bad week with my C4, last week on Thursday I put my car in for it's 75k service and a dist belt change (mine had broken and I was looking for the power gain :-). I also asked my garage to run a compression test as I had some concerns that some damage may of been done by the dist.

As Wednesday rolled around I was looking forward to getting my car back and driving it firing on all 12. On Tuesday I got the call - Mr Williams, we have some bad news - we are getting virtually no compression on cylinder 1 and 6 is half of what it should be........

To say I was disappointed is an over statement, not to mention the potential costs I am going to incure here. I' ve asked the garage to take the engine out to at least investigate the problem further. I'm hoping that at least the pistons are in good shape ?? If that is the case I am planning on having the piston rings, bearings, valve guides and clutch replaced as a minimum. I have also asked the garage to confirm that I have the Flywheel replacement.

Does anyone have any silver linnings on this one ?? or any other recommendations on things to replace whilst the engine is out ?? I'm gonna need to try and keep this down to $6000 which might be tough if the pistons are dead.......

Thom Fitzpatrick

It's a great opportunity to upgrade to a 3.8!

apw964

I wish I could afford the new pistons :-)

Kevin

Hello
I might have ask the shop to run a leak down test. From that you would have been able to narrow your scope of engine problems. If air is coming out of the intake plenum you have a bad intake valve, or guide problem, if air is leaking out your exhaust you have a exhaust valve problem or guide, if it is your ring, whether broken or worn, the air noise will be forced through the breather, because the air is being compressed passes the rings and into your crankcase. Regardless, you are looking at a topend rebuild, one important issue is replacing the rod bearings, the rods can be removed without cracking your engine case. You can have ARP, or Raceware rod bolts installed. Good Luck.

JBH

APW964 (insert your name here):

A few things I don't understand - you drove the car in for 75K service and distributor belt change and all of a sudden there is zero compression in one cylinder and only 50% in another? I looked at you previous thread on loss of hp when the belt breaks, but you never mentioned having problems that would indicate cylinder failure.

The other thing that bothers me is that you lost two cylinders - maybe it's my lack of understanding of the ignition system, but I can't see that happening with a broken distributor belt.

I would not have the service guys take your engine out just yet. Get the leakdown information suggested in the previous post - try to witness the test to see the results for yourself. I would also recommend shopping around - are you sure the shop you selected is the best for overhauling your engine?

Finally, would you mind providing a little more information about what happened leading up to the 75K service.

Jeff

Kevin

I have read the post regarding the broken distributor belts over the last few days. One of the important reasons to replace the belt is that you will have one cylinder always firing. Please picture that as the belt breaks the left rotor stops on a cylinder. The coil will continue to fire at all the time, the injector will be supplying fuel to that cylinder, but it will be igniting the fuel to early and to often because an adjacent cylinder caused it to fire, remember that the rotor is stuck on that cylinder, it should cycle to the next one and fire the next cylinder but it doesn't. Here the point, the disturbance caused by the constant ignition, with fuel or without it, with the valves open or closed on that cylinder add considerable amounts of stress to the components in that hole. Temperatures increase and oil that is used for piston lubrication is burnt off, stress on the rings are increased. Temperature caused detonation, the cooling effects from the normal 4 cycle process is cancelled due to the constant firing of the stuck rotor. Detonation kills the rings, and destroys pistons, the rings will break. It would be interesting to find the result from APW964, I would think that the damage done would be from detonation. And yes, Adrian has mentioned that the Brain will retard the ignition timing. It does, but it will not cancel the signal to the coil. The plugs will fire at 40,000 volts and ignite or try to ignite the premature mixture. Bruce Andereson has also written about these facts in previous articles.

JBH

I have read the same and I think the results from the work done on this engine should provide some insight. If a hole was burned in the piston, a leakdown test should reveal that.

I was really puzzled by the fact that one piston had no compression (presumably the one where the coil fired continuously), but the six piston had only 50% compression. Perhaps that was bad before the belt broke.

It is still my advice to do more diagnostics before pulling the engine and starting an overhaul. I think it always advisable to witness these tests - you protect yourself and learn something about your car.

Bill Wagner

apw964:

I HATE to sound like a complete cynic, but are these guys trying to take advantage of you? Having a hole blown in a piston due to a distributor belt breaking and forcing the a wiper to stop directly over a contact can happen but it IS a rarity. Prior to taking the car in, did you have any of the following symptoms:

1. VERY rough idle?
2. Noticeable knocking and/or pinging?
3. Backfiring?

If you had no compression on one cylinder and another one marginal as well, I would think that your idle would be VERY rough...so rough in fact that you wouldn't want to drive the car.

There has been an ongoing debate between myself and Adrian (in case you haven't noticed) regarding the distributor belt. My stance is that if a possibility of a bad distributor belt STANDS EVEN THE SLIGHTEST CHANCE of ruining an engine, then it needs to be taken seriously, regardless of how remote. He seems to me to differ in his opinions, but I can't speak on his behalf.

In any case, regardless of who is right or wrong, BEWARE of less than honest mechanics. I just got through dealing with a shop that was a PCA sponser that did one of the worst "repair" jobs I've ever seen in my life....I had to have it re-done at another shop!

For the distributor belt to actually damage the engine, the rotor must stop on top of, or very near to one of the contacts. Can this happen: YES! Is it probable: NO! If the rotor contact on the wiper is not close enough to one of the contacts on the distributor itself to generate a spark between the two, all you will receive is a slight loss of power and NOTHING MORE. I hate to sound like a cynic once again, but if you took the car in to these guys and informed them that you were worried about about engine damage, they MAY have decided that this was a golden opportunity to milk you for an engine overhaul. If, on the other hand, there were SERIOUS and OBVIOUS signs of engine malfunction as I stated above, then maybe I your engine really is shot. Engine knock, if allowed to go on for any period of time WILL put holes in pistons, but even as such, it doesn't neccesarilly mean the distributor belt itself is to blame....there are 1000s of other malfunctions that can cause engine knock.

The reason I'm so concerned about this is because I've never heard you complain about engine performance, rough idling, or engine knocking before.

If I were you, unless you REALLY DO have a rough idle and are experiencing knock/pinging, I would just show up at the shop (without warning) and say you want to take the car home (this will prevent them from "introducing" problems...have it put on a flatbed and moved home...anything beats $8000). Make up an excuse. Blame it on the economy...tell them your stocks are down and you can't afford the repair right now. THEN take the car to another shop and DON'T TELL THEM ABOUT THE DISTRIBUTOR BELT!! Ask for a compression check and see how it goes. If it comes out OK, ask them to check the distributor belt. If on the other hand it fails the test, then you obviously have a problem and at least you'll have two shops to compete against for repair prices.

I hate to sound this negative, but your talking big bucks, and I hope this helps,

Bill Wagner

apw964

Kevin / JBH / Bill,

Thankyou v much for the advice. I went into the garage on Friday to discuss the potential costs involved, and also what makes sense to overhaul. I essentially have the w/e to consider their estimates and also the intergraty of the garage.

The garage itself is PAR Cars in New Rochelle just outside of NY. Has anyone in the new york area had any expereince with these guys ? I don't want to point the finger at them as they have been a reliable and helpful garage to date, in fact I believe that they are all PCA members, and obviuos enthusiasts.

Bill - You mention that the car would probably run with a rough idle if it was runing on 4.5 cylinders - this wasn't the case. The car was definately low on performance, and suffered from pinging (signs of a broken dist belt for sure), but rough idle - no, knocking - no, and backfire - no

My problem is I do not know enough to accuse them of telling me anything but the truth, and to date I have been impresed with their work. I am however feeling cynical myself.

P.S : APW964 = Andy

Michael Delaney

apw964, I've read these post several times and one thing I don't understand is that if when you took in it at that time had zero compression on 1 cyl. and half on another the car should have been running terribly. A six cylinder engine basically running on four cylinders would not have made me think I needed a 75K service. I would have been looking for phone numbers for a tow truck. Was it running that bad when you took it in? I mean bad. Roy Eames '91 C2 Cab

JBH

Andy:

The best thing to do is get a leakdown test - this should answer all questions. It is not expensive and you can witness the test to ensure what they are saying is the truth.

I would not hesitate for a moment to take the car to another shop - this is no reflection on PAR, it is just a smart thing to do. You have every right to get two opinions and shop around for the best repairs, should they be needed.

Please let us know what you are doing and the outcome

Bill Wagner

Andy:

I was kind of hoping you would say "the car was running great when I took it in". Unfortunately, since it had signs of having problems my suspicious about the shop are probably unfounded, or somewhat exaggerated (it's amazing how a few bad experiences with shops can make me completely paranoid).

Regardless of whether or not you decide to take the car to another shop, I would still not assume that the distributor did this. If they do a test on the distributor and it shows it constantly firing on pistons 1 or 6, then the distributor is most likely the culprit and you may really be one of the very, very few people that run into this problem (4th that I know of out of probably thousands of cars). A lot of things can cause the pinging, and needless to say the cause needs to be identified. I still think I might want to get a second opinion on the status of the car. When I listed backfiring and rough idle I was not implying that these were the symptoms of a distributor belt problem but of someone running on essentially 4 cylinders out of 6.

A local PCA member had his distributor belt break and lock right over one of the spark plug contacts. In his case, he had severe pinging, knocking, and a noticeable lack of power (sounds similar to your description). He took it into a shop and they replaced the distributor with a rebuilt one and did a precautionary compression and leak down test, and found the engine to be in good shape.

What year is your car, and how long did it have the symptoms before you took it in?

Best Wishes,

Bill Wagner

Kevin

Andy;

As mentioned earlier, a leakdown like others have suggested will shed alot of light to your engine condition. You might make it known up front that you want to get another opinion from another shop. PAR should understand your concerns. You also might want to call Ollie's Automotive Machining Inc in CA, they do alot great work. They can give you prices for machine work, heads, rods, and P & L blueprinting. (714) 558-7334.

Adrian

Okay Guys,
I have to answer Bills posting first. I happen to agree with most things you say. I just disagree with the language used and statements without the all the facts tabled as well.
Since this thread blew onto the board I have done a lot of research and sought answers to my questions from many respected quarters. I have learned a lot on this subject.
I must change my blanket comment ( I am also guilty of making blanket comments) of breaking the belt will not cause damage to, "a broken belt will not cause damage in the short term" but if left unrepaired may well cause terminal damage if you ARE REALLY UNLUCKY. I mean by this, that if you detect a broken belt, you do not need to get towed to the nearest repair facility. However you cannot drive across America to get home first either. Let common sense prevail.
Now some basic questions and answers.
Can a broken secondary distributor belt burn a hole in the top of a piston?. Answer: Yes it can.
How?. If the distributor rotor stops inline with a cap contact and stays there and keeps the spark plug firing all the time and the spark plug survives this etc etc.
Is there protection built in for this?: What protection is installed is not adequate for the job if the spark plug keeps firing non stop forever.
Is there a fix for this?. Yes there is, the vent kit and a regular 12,000 mile inspection.
Is this fix adequate?. In the data I have received back, yes it is but a belt replacement is recommended by USA based people at 50,000miles and here in Europe at 60,000miles or every 5 years REGARDLESS. Absolutely no different to the overhead cam belt recommendations that are often ignored as well, especially on 944s and 968s.
How Many Holes in Pistons have been found?. Again from the data I have received back, very few. All reported to myself have been on the race track..
Can the average 964 driver identify the problem quickly?. The answer is no!!!. They feel something may not be right but do nothing about it. THIS IS THE SINGLE BIGGEST MAJOR PROBLEM. IF YOU THINK SOMETHING IS WRONG WITH YOUR 964 GET IT LOOKED AT.
How long can a 964 be driven in the worst case scenario of the rotor and cap contact aligned before terminal damage occurs?. For the average 964 driver who drives on the road estimates vary but the mean average seems to be around 5000 miles. On the race track, maybe the next race. For the rest, somewhere inbetween.
Which 964s are most likely to be affected?.
(1) USA versions.
Why?. Technical Service Bulletins to rectify problems were rarely incorporated. Only people in the know had this work carried out. However any 964 anywhere in the world without the vent kit installed runs a higher risk of having a broken belt and no knowing it and Possibly damaging their engine over time.
(2) 964s which have been modified to improve performance, including installation of hot plugs but do not have the basic TSB improvements carried out. No vent kit "Very high risk" of damage if belt breaks.
(3) Racing versions that retain the secondary belt drive system.
Conclusions:
Porsche made a failure when they designed this system. It took time to show itself. Porsche came up with a solution which works. (They should have done more but this is only my opinion) Vent kit and regular scheduled inspections.
The experts around the world agree that the vent kit does solve the problem for reliability purposes and to manufacturing standards.
So what are we left with.
964s without Vent kits installed.
964s which do not get the full service done properly every time.
964s with a problem but not looked at.
Bascially it is a care and maintenance issue in 2001.
Is it a serious problem?. To me this problem is no more serious than running out of oil, or leaving the cam belt (not on a 964) until it breaks. Purely from a statistical point of view of course. The destruction of any individuals engine is a major serious problem for that person but not necessarily for the whole series.
It really is "very rare" for normal average 964 owners to trash an engine because of this problem.
This is an easily avoidable and preventable problem, not a 964 "nasty Porsche hidden design failure" problem.
Recommendations:
1/. Install Vent Kit and New Belt Right Now, today, make this go away right now. Call Steve Weiner and spend your 150 bucks or install the belt and kit yourself.
2/. If you have the vent kit installed already but have no receipt for a distributor belt, and you have more than 50,000 miles on the clock, call Steve Weiner and spend your 150 bucks or install the belt yourself.
3/. If you have more than 50,000 miles on your secondary distributor belt, REPLACE IT.
4/. Ensure when you have the normal service (and please remember in the USA you guys go 3000 miles more than we do here in Europe)
that the #1 and #2 ignition functional check is carried out correctly.
5/. If you notice or feel something is wrong. CHECK THE BELT FIRST. Pop off the distributor cap and check it.
6/. If you install performance enhancing mods and regularily use the race track for any reason, CHECK THE BELT every 3000 miles and change it every 15,000miles.
7/. If you race a 964 full blown, you are on your own. If the belt breaks you are going to more often than not blow a hole in your piston. This is called BAD LUCK.
Summary:
Care and Maintenance is the key. Look after the 964 and it will look after you. If something is wrong, please fix it. This is not a hidden problem unless you hide it.
Ciao,
Adrian
911C4

PS: If you post a problem like apw964 then may I ask that we get the whole story and not in parts. I find it strange that somebody is driving around with no compression on one cylinder and only half on another and didn´t notice anything wrong. However I have been told this is quite normal. I have attempted to move forward with an auto which had a hole in the piston. I did not know what the problem was at the time but the Escort RS2000 certainly told me I had a terminal problem. It did not want to move forward quitely.

Adrian

Just to let you know that no funny business is going on. I decided to close off the other two threads running on this subject to concentrate everyone back onto this one. The summaries of research are here.
I also have a small problem as well, highlighted by Jeff. Who is apw964???. I sincerely hope we do not have story teller here. I have emailed apw964 personally for some details.
This is a serious story of woe but I hope it is a true story and not some attempt to create problems that do not exist. I am always concerned when people do not identify themselves, especially with such a problem.
Ciao,
Adrian
911C4