ebaker

Evidently the turbo motor is prone to excessive wear on the crankshaft thrust bearing, resulting in excessive crank end play. I assume the is due to the heavy clutch pressure plate pressures. Does much of this wear occur at engine startup, when the clutch is depressed and the oil pressure is zero? I don't think you have to press the clutch on Canadian or Euro cars to start them(?) Would deactivating the USA clutch starter lockout significantly reduce the thrust bearing wear? Is there an easy bypass, such as pulling or jumpering a relay?

t urbo

Dont know about the thrust bearing but i do know that on my UK car you dont have to depress the clutch pedal to start it! Which is lucky because my pedal losses pressure overnight and is a ba****d to push down when the engine is off.

Oak

ebaker, never heard of any issues of premature thrust bearing wear? I would think this would be more of an quality control issue during assembly (double chekcing end-play during assbly) and or bearing material failure, than having to depress the clutch during start-up unless the TO bearing has seized. where did you hear that this has been a problem?

ebaker

I think I've seen it mentioned more than once. I'm not sure it is an issue. The (power assisted) force on the throw out bearing is applied to the crankshaft thrust bearing.

Oak

that's not really an issue. I thought it was something of signifigance.

PorschePhD

Uh, it most certainly is an issue. When you find 6K mile motors with a worn thrust you certainly will have premature wear issues in other areas. The thrust rides the shoulder of #1 journal. To say that a main bearing prematurely wearing is not a significant issue is irresponsible. It has shown up in about every motor torn down. In fact if you look you will not find an end thrust play spec. You will have to look else where.

ebaker

PorschePhD, do you think bypassing the USA clutch starter lockout will reduce wear?

cjv

Yes it will reduce the wear. We have proved it on KA. The last motor was set up to start without depressing the clutch.

ebaker

Do you know how to do the bypass? I tried comparing Canadian and US wiring diagrams but I couldn't find the difference.

Oak

wow I have never heard of anyone with a worn out thrust bearing at 6k. Seems as if this were that common it would be much more static and complaints. (996 rms) This is the first I have heard of this. But at 135k miles I would hardly consider it a problem.

PorschePhD

The ECU program is a tad different. You can jumper the switch. Maybe Chad will chime in with how they do it. That however is only half of the issue. The drag on the single serpentine belt is the other issue as well as the valve train drag. The force it takes to turn that motor over compared to the older motors is more than double the force.

Oak,
Unless you have been in a TT motor I wouldn't expect that you would be privy to the issue. The guys that have motors replaced from rattling on startup is caused by what?? Oh, the thrust issue. Porsche gives no reason as to why, only that they will replace it. It is not something that has been said publicly. It is well documented though. It is a problem if you know what the true thrust measurement is on this motor and motors of the past. As I said, unless you are in the Porsche circle and build motors I highly doubt you would have any idea this is an issue. I have the set of 6K mile bearings from an 02’ Gt2 we just did if you would like pictures of them. This is just the recent set. I have many more. Just let me know and I will get them right over.

Black Sea RD

Stephen,

Has the trust bearing wear issue been found in the Tiptronic 996 TTs as well?

Constantine

vyper340

PPHD - what other info can I find about the rattling at start-up and if there are any TSB's so I can have the issue addressed if mine demonstrates it?

I would like to see the pics of the 6k bearings and learn more about this issue...

I am hearing some rattle in the engine at start-up and would like to have the issue addressed before my warranty is out in a couple of years. Thanks!

PorschePhD

The original rattle issue came up as a TSB for a oil check valve which did nothing. Then there was one on the cam adjusters. None of it changed the issue. You will find nothing on the thrust according to the dealer, but I know PCNA knows that there is an issue. Most of the time they do a resistance test on the crank. Which I find comical.

The tip does show the same issue. I have done them with 30K +/- Miles and the issue is still present.

I will post pictures on Mon. I don't have them at the house.

cjv

We deactivated it through the ECU.