Thrust Plate problem w M96 motor

[BoxsterGT]

I wonder if anyone else has experienced this problem...........

When draining the oil in preparation for doing a IMS bearing upgrade, we noticed a small metal piece stuck to the magnetic drain plug we always fit to the M96 motors as a precaution.

It is a piece from one of (2) thrust plates or thrust washers used at bearing journal #3 to limit the crankshaft end play. The PN is 996-101-129-51 which supercedes to 996-101-129-52.



We have dropped the oil pan and found the remaining piece of the half-moon or crescent shape thrust washer or thrust plate laying in the pan.

The vehicle is a 2001 Boxster S 3.2 with about 45k miles. It has been fitted with a belt driven supercharger and is driven on the track on a regular basis.

It runs & drives as if there are no issues at all. No strange noises or clunks. The crankshaft moves back & forth with about 1/4in end play. We believe the 2nd thrust plate is still somewhere up inside the motor waiting to drop down onto the pan.

Again, the motor ran as normal. However, its likely it won't for much longer.

Anyone with lots of track miles experience anything like this?

Len at Autosportengineering dot com

[JFP in PA]

This is not good. We have seen the locking ears break off before, and the resulting crank end play was way out of spec (0.0045). Problem now is that replacing this $12 part is an absolute ***** as it sits inside the crank carrier.....

[EBS_Don]

Everyone one of the engines I have been into shows serious wear on just one of the thrust bearings. Every time you disengage the clutch it forces the crank against this one small bearing while the shell on the other side likely still looks like it's brand new! This is a chronic issue with all of these engines and it may be time for a solution.

[JFP in PA]

Perhaps one of the dumbest things we have ever seen is to find the part installed backwards (the side in my left photo facing the crank rather than the one in the right photo with the obvious oil grooves in its surface).............

[BoxsterGT]

Thank you JFP!

Is there any chance that there is no damage internally save for replacing these thrust plates?

Is it possible that a teardown & reassembly is all that is needed?

Is this another example of a design snafu?

What would cause this to happen? The car was extensively track driven, may have even been oil starved in certain corners of certain tracks.

Len

[EBS_Don]

Here's a pic of two bearings that came from the same engine:

[EBS_Don]

A lot of stop and go traffic or a high clamp load pressure plate would not help this situation!

[JFP in PA]

Originally Posted by BoxsterGT

Thank you JFP!

Is there any chance that there is no damage internally save for replacing these thrust plates?

Is it possible that a teardown & reassembly is all that is needed?

Is this another example of a design snafu?

What would cause this to happen? The car was extensively track driven, may have even been oil starved in certain corners of certain tracks.

Len

If the thrust washer is out of place, the steel crank is resting on or striking an alloy crank carrier, which ain't good. This part is a "wear item", particularly if you are running a clutch with higher than stock clamping pressures. Personally, I would not run an engine that has one out of place. A rebuild is the way to go, but carefully check the crank endplay, you may need a new carrier as I do not believe these are available in larger thicknesses.

As for why it happens, the answers are all over the map; we have seen them fail on gingerly driven streetcars, and live long lives on cars that regularly get the crap beaten out of them. My pet opinion is that the quality and temperatures of the oil come into play and that once they begin to wear; crank movement increases and finishes the job. And, as I have noted, every once in a while we have seen one installed backwards, which leads to a short and inglorious life........

[BYprodriver]

Originally Posted by EBS_Don

Everyone one of the engines I have been into shows serious wear on just one of the thrust bearings. Every time you disengage the clutch it forces the crank against this one small bearing while the shell on the other side likely still looks like it's brand new! This is a chronic issue with all of these engines and it may be time for a solution.

This has been my experience also, I just replace the worn side.

[KNS]

Is this a problem with all M96 engines?

[BoxsterGT]

Yes. Its just another design snafu w/ this motor!

Len

[EBS_Don]

Interestingly enough, the current generation uses the same exact setup. In fact it's the same part number used since the introduction of the 996 3.6 liter engine...