dporto

I'm not sure I'm understanding how disengaging the clutch is creating a thrust load on the crankshaft??? Wouldn't engaging the clutch release the load on the flywheel/crank?

Flat6 Innovations

The pressure plate in the clutch system is over 3,000 pounds of force. When the clutch pedal is depressed the release bearing contacts the pressure plate to release the clutch. To do this, it must fight the load of the pressure plate.

So, since the pressure plate is attached to the flywheel, and the flywheel is attached to the crankshaft, this force is placed longitudinally on the crankshaft. Its the job of the crankshaft thrust shims to carry this load.

But at start up there's little lubrication on these shims, so the forward facing shim is solely responsible for carrying these forces made by the pressure plate. If the clutch is depressed to start the car, then this makes for the worst possible scenario for the crankshaft thrust shims, as they start dry, and with all that load.

This makes them wear thin, and fall out of the crankshaft carrier... Then the crankshaft starts banging around, and when you pull off the oil sump to help diagnose the issue you are faced with whats left of the shim laying on the sump plate.

I documented this as mode of failure #17.

Chris(MA)

is it possible to slip a new thrust bearing from underneath by removing the sump plate?

dporto

Got it! Makes so much sense... Looks like I'll be jumping my clutch lockout switch. Thanks for the explanation Jake

Flat6 Innovations

Hell NO!

These thrust shims (2) are the VERY FIRST part thats installed when reassembling an M96 engine. Once the crank carrier is assembled, it holds the shims captive, and they can't even be seen.

This one is a 100% teardown to remedy.

That clutch switch is a really stupid addition to these cars, mechanically speaking. Any car I won has any switch like this bypassed, and I start the engine with my foot off the clutch, transmission in neutral.

Of course, I am the type that rips every safety switch off every piece of equipment, or car that I own. If I hurt myself, its my own damn fault, but I'll be damed if some safety switch is going to fail and leave me on the side of the road, or in the middle of a field!

Mark Henry

In fail mode it's done damage even if it doesn't fall out.
I have a very expensive paperweight on the bench.

Flat6 Innovations

Yes, this takes out the crankshaft, and carrier quickly. It will also shed a massive amount of material to contaminate the rest of the engine.

Volkert

Thanks for sharing that insight!!

Volkert

Mark Henry

At least it was caught in time, just the crank.

Just in time....

dan_189

Interesting to hear about the clutch thanks. MY Aus '04 can be started without depressing the clutch so ill have to get used to doing that.

sfv_rider

If you bypass the "clutch depressed" switch, does it affect the cruise control operation?

JohnCA58

No, it does not.

dporto

I would think that the cruise will not work with the switch "jumpered" - under normal operation the cruise drops if the clutch is depressed... perhaps a way around this is to wire a switch (one of the open dash positions?) that will jump the switch without pushing the clutch pedal. Once the car has started, you can turn the pedal switch back "on" which will allow the cruise control to operate as it normally would - i.e. Drop off if/when clutch is depressed.

islaTurbine

Mine starts without the clutch and cruise operates normally. I do need to look underneath to see if it was jumpered by the last owner or if it has a RoW ECU flash. I've heard that the flash disables the clutch requirement for start as well.

Eury

It's not an issue, the cruise uses a different switch. I bypassed this switch this weekend after reading Jake Raby's post. Took less than a minute and my cruise operates exactly the same as it did before.