greenbe

It would be nice if someone could post some M96 warranty prices from the last few months and the various starting mileage levels avaialbe and maximums. I agree you are going to want some combination of warranty and preventative maintenance, and the mix is probably going to vary with age and warranty availability/pricing.

I never intended to scare anyone into thinking these engines are timebombs. This just happened to me, and I was looking for some help (which I got). As it happened to some others. Nobody seems to know the actual numbers and age distribution of the failures, it could turn out to be still a relatively low %. Whatever happens just drive the car and enjoy it and don't worry so much. It is still the best car I ever owned. Get out there and put some cross-country miles on it. At least I enjoyed 38K miles worry free.

jrgordonsenior

greeenbe:

Did you contact Auto Strasse and if so, did you ask about their IMS bearing?

greenbe

Yes I did talk to Auto Strasse, I thought they were using LNE for the IMS but I will check again next week.

greenbe

It's time to stir the pot on this thread again :-)

An interesting thing happened while I was talking to various people trying to find a solution. Two people I spoke to live independently said that the problem is more likely a snapped cam chain than a blown IMS bearing. In neither case did I get the full detail, but something about a tensioner and the tendency to go "on one side first" seemed to be in common. Everyone else blamed the IMS. What is interesting is these two people seemed to have their hands in watercool engines fixing them regularly, with a focus on street cars. Everyone else was either racing focused or was relaying information 2nd hand. One of them went so far as to say the IMS issues were "urban legend" and the only IMS failures he saw was due to poor-care, specifically oil that was completely black and could not flow to the bearing.

I don't know what to make of this, but time will tell. As I speak the car is heading to Southern California. If things go according to plan by the end of this week it will be broken down and I will have a root cause. Pictures will probably take another week or two until I get there and claim the bad pieces, which should make good paperweights.

soverystout

Well put +1

Brucechas

Good luck sir, with this situation.

greenbe

Well, the verdict is in. The engine is completely in pieces. I don't have the full writeup and pictures yet, should get those in 1-2 weeks.

Based on first verbal information, it looks like the cam chain tensioner to bank 1 (drivers side) siezed up. It was not audible or noticeable. After some time the chain skipped a tooth on the large gear from the IMS damaging that gear (that probably caused the CEL) Then the chain snapped. The "clackity clack" or "marbles" sound was likely the flapping chain. I got a few bent valves but luckily no damage to the cylinders.

The IMS bearing is just fine. I need a new IMS (the shaft itself) only because the gears that drive the chain are damaged beyond repair.

What is interesting is this is exactly what experienced rebuilder #1 told me right at the beginning of this voyage. I ended up going with rebuilder #2, for other reason, who also guessed it was unlikely to be IMS bearing unless the car was in an abused state. I will have pictures to prove all this, including of course a picture of my pristine IMS bearing.

Does anyone know anything about the lineage of chain tensioners? He says at some point P changed the design of the tensioners, but this car has the newer tensioner design (P original). Rebuilder #1 also said it tends to go on one side first ... I never captured enough of the details. But I can see that logically since the direction of drive force on the chain will be with and against gravity depending on which side. It also plays into what rebuilder #3 said which is that the strain on the cam chain is highest at idle since there is the least backpressure on the valves, and yes this is my daily driver and favorite car with a fair amount of stop and go (although at least half my miles have been on long trips).

Any information here would be helpful.

Ahmet

So will you get out of this with just a head job +shaft? That's sort of what it's sounding like. Shouldn't be too bad, $3k maybe?

rb101

When I pulled the tensioners for the IMS bearing upgrade, 2 of the 3 were badly scored. The crank to IMS (see picture) was the worst one followed by 1-3. 4-6 was in perfect shape, but I replaced all three. I originally put the newest IMS tensioner in, but later put in the old style after reading the tech bulletin about not mixing new and old styles. The tensioners had 105K miles when I replaced them.

Rick
99 996C4
87 944S

Brucechas

Great info, Thank you sir.

greenbe

That was not offered by anyone. Most seem to want to take it completely apart, thoroughly clean it with an ultrasonic wash in case any bits of metal get in there, and then rebuild it replacing and upgrading various components as necessary. Current estimate is $8K-9K including 1 yr 12K mi warranty. I'd be willing to take the risk given the price detla, but they weren't. I spoke to about 5 people across the country with direct experience in the matter.

Only one of them held out a glimmer of hope in the <$3K range, but was not available. So that is theoretical. In this situation, you also have the practical consideration of getting it fixed vs having it sit in a shop while you talk about it forever.

greenbe

Can you please provide me a reference to this tech bulletin so I can read it and learn?

Excellent information, I second that comment. And again, you are the 3rd person with direct knowledge to mention the tendency of bank 1 (cyl 1-3) tensioner to go, while 4-6 often is fine. I don't know my crank-to-IMS situation at the moment, I will learn all this when I recover the damaged parts and take pictures next weekend.

Do you know if you had the "old/original" tensioners or the redesigned ones?

greenbe

To clarify my last comment, I see you talk about new and old tensioner, but I am not clear how many redesigns there have been on this, 2 or 3, and what you mean by new. Needless to say I am greatly interested in information on this.

rb101

the TSP is:
10/00 #1551 New Drive Chain and Seal for Inter. Shaft

you can get it if you are a member on RennTech.

http://www.renntech.org/forums/index...ownload&id=148

Rick
99 996C4
87 944S

Geeforce

Subscribed to see the outcome.....