Throw out bearing chirps when clutch is engaged

[98legacy22stick]

As the subject states, when the clutch pedal is up, at idle, there is a chirping sound coming from the throw-out bearing at approximately one chirp per revolution of the engine. This sound goes away if I depress the clutch pedal as little as .25 inches.

My theory is that the throw-out bearing is barely touching the pressure plate, causing a differential motion between the two resulting in the squeek.

To address this problem, I tightened the clutch cable adjustment until the chirp went away. Clutch pedal freeplay within limits ie. not too tight but it is difficult to tell because of the integral spring in the clutch pedal.

My general question is: is the throw out bearing intended to spin when the clutch is engaged, or only when disengaging the clutch?

It seems as though the adjustement i made put enough pressure agains the throw-out bearing to ensure that it is always spinning with the pressure plate, although it will be very lightly loaded when the clutch is engaged.
Is this detrimental to the throwout bearing or just proper adjustemtnt?

I should mention that this problem began occurring after I replaced the clutch, flywheel, and throwout bearing, so all hardware is new. I made sure to grease the throwout bearing bore and contact points with the clutch fork.

[98legacy22stick]

Well, I investigated a bit more. Most of what I said in the above post was wrong. I adjusted the clutch pedal free play to ensure it was in spec (at the time of my previous post, it was too tight) With correct clutch pedal free play, the throw out bearing is still in constant contact with the pressure plate. The chirp also returned but I was able to confirm that it is not a chirp due to differential speed between the throw out bearing and pressure plate. It is a vibration. When I very lightly touched the clutch for, the chirping sound went away.
Maybe it is the combination of a new throw out bearing on a slightly worn transmission snout that creates a looser fit resulting in more movement. In any case, my strategy for eliminating this problem will be to stick a brush with hi-temp grease down the hole in the bell housing and apply to the area where the throw-out bearing slides, as well as any other areas I can get to without risking contamination of the clutch disk. I also might tape a small weight to the clutch fork to try and change the vibrational characteristics. I'm concerned that at higher speeds, any vibration, over time might be causing premature wear of the throw out bearing and transmission snout. Maybe I’m being a bit over conservative, but at a bare minimum, the chirp is an annoyance. Has anyone else reading this experienced this kind of problem?

[Legacy777]

Is this on a turbo or non-turbo car?

I had a somewhat similar issue with mine when i did the AWD & 5spd swap. I believe it was the plunger rod of the slave cylinder that was causing the noise. I believe how the MC works is that it is supposed to relieve the pressure back to the MC. If I remember correctly, I adjusted the MC push rod ever so slightly to restrict he amount of movement the slave cylinder rod could do.

[98legacy22stick]

Thanks for the reply. Unfortunately, it's a non turbo. So I don't have any clutch hydraulics to adjust.

[Legacy777]

Hmm. Was the TOB & clutch parts you put in OEM, or another brand?

[98legacy22stick]

Sadly, the parts are not OEM, although if I were to do the job today(put the clutch in over a year ago), based on what I now know, they would be OEM parts. In any case I was picking up some parts at the Subaru dealership (noticed that the clutch fork boot was torn) and I asked a mechanic about the squeaking. His reply was that it was normal, and furthermore impossible to permanently get rid of. I'm going to give it a shot this weekend, but its good to hear from someone who is familiar with the sound, that it is not serious.

[98legacy22stick]

Well, I replaced the clutch fork boot over the weekend and inspected inside the clutch. TO bearing looks fine. Pressure plate fingers have normal wear and a normal contact pattern. I took a brush and re-greased as many of the contact poitns as I could with some hi-temp grease. The chirp seems to have quieted down/disappeared alltogether. But if it does come back I think I'll just leave it alone as it doesn't sound like a real problem.