What causes thrust bearing failure?

[20ls01]

I was reading on this topic and it got me concerned since i have a 6speed manual.

I was thinking..I did the clutch delay valve delete(reduces drivetrain shock) and was wondering if this can contribute to thrust bearing failure.

1. What causes this on our mk7/mk7.5 platform? Bad engine design?
2. Any 2018 GTI's with engine failures because of this?

 

[mr wrong]

This is purely my opinion, and I'm not suggesting anyone bypass an important safety feature, but I don't think depressing the clutch pedal which applies force to the thrust bearing on startup helps since there's no oil pressure. On my earlier manual VW's I always started the car in neutral and never pressed the clutch pedal.


Again this is purely anecdotal.

 

[MSchott]

This is purely my opinion, and I'm not suggesting anyone bypass an important safety feature, but I don't think depressing the clutch pedal which applies force to the thrust bearing on startup helps since there's no oil pressure. On my earlier manual VW's I always started the car in neutral and never pressed the clutch pedal.


Again this is purely anecdotal.

Are you saying because it’s not being lubricated due to the cold engine? If so, does the clutch see engine oil at all?

 

[Finglonga]

Keeping or resting your foot on the clutch pedal seriously will shorten it's life because it ads a small bit of load on it constantly.

 

[mr wrong]

I'm talking about the un lubricated lateral force applied to the crankshaft and thrust bearing when the clutch pedal is depressed on startup

 

[eXult]

This is purely my opinion, and I'm not suggesting anyone bypass an important safety feature, but I don't think depressing the clutch pedal which applies force to the thrust bearing on startup helps since there's no oil pressure. On my earlier manual VW's I always started the car in neutral and never pressed the clutch pedal.


Again this is purely anecdotal.

We can't do that on MK7s can we? First manual so I apologize for the newbie questions, but I can't turn the car on without pressing the clutch.

 

[MSchott]

I'm talking about the un lubricated lateral force applied to the crankshaft and thrust bearing when the clutch pedal is depressed on startup

Sorry still not understanding but I can tell you my 64,000 mile 2017 which has been subject to well over 1500 cold starts has shown no signs of clutch issues. My guess is these issues are more due to poor technique, at least in unmodded cars.

 

[JerseyDrew77]

We can't do that on MK7s can we? First manual so I apologize for the newbie questions, but I can't turn the car on without pressing the clutch.

On the MK7's you can't. You have to press in the clutch pedal in order to start the car.

 

[dietcokefiend]

The thrust bearing is sandwhiched between the crank and bearing caps inside the engine block. Its the bearing that keeps the crankshaft centered when pressed on (pressing your clutch pedal works against this bearing).


The clutch is outside the engine, the thrust bearing is inside the engine.

 

[oddspyke]

I know there are lots of different clutch designs, but I keep hearing this logic repeated, and it sounds totally backwards to me. The flywheel is fixed to the crankshaft, the far end of which has the thrust bearing. When the clutch is released (foot off pedal), the throw out bearing is relaxed and the pressure plate is pushing the clutch against the flywheel, applying axial load on the thrust bearing. When you depress the clutch, the throw out bearing compresses the pressure plate and should remove the axial load.

Also, I think this is a moot point since our oil pumps fire up before you start the car.

 

[Strange Mud]

afik oil pumps are gear driven...VW may have an aux oil pump for turbo cool down but oil pumps really don't run b4 engine does.


interesting idea about clutch delay valve....

 

[russiankid]

I know there are lots of different clutch designs, but I keep hearing this logic repeated, and it sounds totally backwards to me. The flywheel is fixed to the crankshaft, the far end of which has the thrust bearing. When the clutch is released (foot off pedal), the throw out bearing is relaxed and the pressure plate is pushing the clutch against the flywheel, applying axial load on the thrust bearing. When you depress the clutch, the throw out bearing compresses the pressure plate and should remove the axial load.

Also, I think this is a moot point since our oil pumps fire up before you start the car.

What you described is not true. The flywheel mounts to the end of the crankshaft and then the pressure plate mounts onto the flywheel. In between the flywheel and pressure plate is the clutch disk which is sandwiched in between the two pieces. When you depress the clutch pedal, the throw out bearing pushes on the pressure plate which in returns loads the flywheel thus pressure on the thrust bearing. When you're not pushing on the pedal, there is no load.

This platform does not have an electric oil pump, only aux water pump. Oil does not take long to reach the bearings as they are already coated with oil and the oil filter canister has an anti drain back valve to build pressure nearly instantly.

The issue, in my opinion, is design and assembly flaw. Hundreds of thousands of engines are produced that have a clutch mounted to them without issues including VW engines. If the bearing was improperly installed, you get premature wear and then it falls out.

 

[Jacobmk7]

Pretty sure there’s no aux oil pump, the sound you hear when you open the door is the LP fuel pump priming. There is an aux coolant pump built into the thermostat/water pump housing to cool the turbo during shutdown though.
To have oil pressure before you start you would need a Pre Oiler.

 

[Inka Orange]

Are the crankshaft and bearings not at least partially in the oil bath already?

 

[20ls01]

interesting idea about clutch delay valve....

right..im curious now if it can contribute to it. I may put the valve back just incase.

Are the crankshaft and bearings not at least partially in the oil bath already?

nooo...if it was, it means you severely overfilled your engine with oil.