Why does my throwout bearing spin constantly?

[DirtRoadRunner]

Background:

 

I bought a 2000 Forester 5MT about 16 months ago. The throwout bearing constantly chirped (squeak-squeak-squeak) with the clutch engaged (pedal all the way up) if the car was in neutral. I ignored it for a year, then replaced it as the sound got worse and worse to the point where I could often hear it with the car in gear while driving around.

 

I replaced the bearing 4 months ago. The sound has resurfaced. I removed the dust boot on around the clutch fork for some investigation, and realized that the outer part of the throwout bearing is constantly in contact with the pressure plate and always spinning as long as the engine is running. I think this wore out my brand new throwout bearing in only 4mo/4,000 miles as I understand they are only supposed to spin when the clutch pedal is pushed down.

 

My question is, why is this happening? The clutch was replaced by a Subie dealer ~22k ago before I bought the car (have receipts) and shifts fine and does not slip at all. Short of installing some sort of spring to keep the clutch fork away, how can I fix this? The noise drives me crazy and I don't want to put in another bearing only to have it last only another 4 months. I'm getting very frustrated with the car at this point.

[naru]

Probably a weak spring in the slave cyl.

 

Clutch cover springs w/unequal pressure resulting in some of the fingers being higher.

Could be bad master or insufficient pedal free play too.

Missing return spring or damage on the TO bearing shaft ,perhaps?

 

On the wierder side,excessive flywheel runout or crankshaft endplay.

[DirtRoadRunner]

I replaced the slave cylinder last June, along with the hydraulic hose.

 

I can physically push the pushrod between the slave cylinder and clutch fork in, after which the throwout bearing no longer contacts the pressure plate. However, as soon as I take my finger off the clutch fork, the slave cylinder pushes the clutch fork right back out, allowing the throwout bearing to spin.

 

Looking at the exploded diagrams of the clutch fork assembly, I can't seem to find a return spring anywhere. Was there one installed from the factory?

 

Pedal free play is adjusted nearly all the way out. Also, I pulled off the pushrod between the master cylinder and pedal (inside the cabin of the car) and at the current settings the master cylinder is not being engaged at all with the clutch pedal all of the way out.

 

How can I troubleshoot this any further? I'd rather not troubleshoot by replacing parts only. I'm trying to avoid taking it to a Subie shop, but will as a last resort.

[Durania]

Dang, wish you had a cable clutch. My Outback TOB spins constantly too. Wondering if my clutch cable is too tight.

[987687]

Dang, wish you had a cable clutch. My Outback TOB spins constantly too. Wondering if my clutch cable is too tight.

 

Your cable is too tight. Loosen it at the clutch fork. There should be some free play in the fork.

[Durania]

Got ya. Will do that next time I drive it.

 

It's been nice here so I been driving the STi.

[DirtRoadRunner]

I rigged a clutch fork return spring this evening. Used a 1-1/4" U-bolt to attach a metal mending strap to the clutch fork, then bolted another mending strap to one of the bolts on the throttle body. Hooked the two together with two 9-lb springs. Total cost was $12 at Home Depot for parts.

 

Seems to work pretty well so far. It is keeping the TOB off the pressure plate fingers while the clutch is engaged and the TOB is silent (it was squealing and whining bad today on my commute).

 

However, I had to readjust the clutch pedal (inside the cabin) so the total travel is far, far less than it was before. Otherwise the first 1.5" or so of pedal travel did nothing to engage the clutch. I have the pedal sitting rather low right now to compensate. I plan to revisit the adjustment this weekend and see if I can't figure out something that works a little better.

Edited March 29, 2011 by DirtRoadRunner