FlyingDog

I have never worked on a clutch before so I need some pointers for what to look for.

I have a bearing/rattling noise when the clutch pedal is up (engaged?) that goes away when the pedal is pushed in just a little (1/4-1/3 maybe). If I lay down next to the car when it's running, it sounds like it's coming from the bell housing, not the torque tube.

I tried pulling the lower bell housing, but the MSDS headers are in the way. If I have to, I'll move them (any tips would be appreciated). With them in place I have about 3" of viewing space in the rear and 1" in the front. There appears to be some surface rust on the part with the fingers. Other than that, everything looks fairly new. There is a white sticker that says "Made in Germany" with a non-Porsche part number. It looks brand new. The guide tube looks silver and a little shiny. The throw out bearing appears to be the old style since I can't see the vulcanized rubber locating tabs. It doesn't appear to be worn excessively in any way, and actually looks close to new. Looking at the top of the release arm, there is a white nylon spacer between it and the upper bell housing. I tried to move the release arm at the top and there is no play (at least when it's under pressure at the bottom.

What could the noise be? Throw out bearing, pilot bearing, guide tube, incorrect adjustment (once and only once did I have to push the clutch twice to go into first from a stop), anything else?

worf928

My bet: Plastic bushing at the top of the release arm lever. It's gone, or in pieces, so the lever is vibrating against the ball stud when there is no pressure on the clutch pedal. Pull the air box and look at the top of the bell housing thus exposed. You will see the top of the release arm and should be able to inspect / replace the bushing.

FlyingDog

The bushing looked and felt fine. I'll try to pry on the release arm and see if I get any movement around the ball.

worf928

Last year my '91 was making a noise that sounded like the motor pinging - uncooked peas in a tin can - that went away with a little pressure on the clutch pedal. I looked at the release arm lever (RAL) bushing and it looked fine. So, I figured t/o bearing and dropped the clutch. The outer part of the bushing - the part that you can see with the RAL on the stud was fine. But, the rest of the bushing - the part you cannot see with the RAL on the stud, the part that is inside the cup on the RAL was gone. So, you might try the small-crow-bar-on-the-RA-trick to get it off the stud to really see if the bushing is there. I've never done that - I'll do it next time - so, I cannot say how hard that trick is - only that some folks have done it to replace the bushing.

FlyingDog

I looked at it some more. The outer part of the bushing is cracked. I didn't try to pry the RA out (just a little side to side) because I didn't know if I'd damage anything. It's good to know that I should be able to replace that bushing that way without having to remove the whole clutch or upper bell housing.

I did start the car again after reinstalling everything. I noticed three problems.

1. The bearing noise seems to only go away with the pedal about 2/3-3/4 down instead of the previous 1/4-1/3. I guess that could be caused by having an air bubble in the clutch line (did not bleed it after the line from the resevoir blew off bleeding the brakes).

2. The soft line to the clutch slave is beginning to come apart.

3. Something around my timing belt is chirping as the belt wobbles. All the sprockets and bearing seem to be going straight. Belt tension is correct and hasn't been overdone since everything was replaced (everything that touches the belt has been replaced except the crank sprocket, its locating washers and lower idlers). The belt walks back and forth about 1/8" right down the center of the cam sprockets. The noise occurs 3 out of every 4 times the belt changes direction... chirp-chirp-chirp- -chirp-chirp-chirp- -chirp-chirp-chirp I have no idea what's causing the wobble, and the chirp is centrally located. It never made this noise before today, even when I had a wobbling cam sprocket and more belt movement.

The one piece of good news from today... I think I have LSD!
...either that or my diff is as screwed as the rest of the car.

FlyingDog

A friend explained some of the noises and problems in clutches to me. From what he said, it's not making throwout bearing failure noises. It sounds like that bushing and some adjustment are the problem. Next time I'm down here to work on the car, I'll replace the bushing, bleed the clutch, and hopefully that will be it.

Thanks Dave, I wouldn't have thought of that bushing after the quick first look.

worf928

Have you noticed a change in the clutch pick-up point?

Hmmm... those clutch slave hoses typically have only two states: Working and exploded. Do you see any signs of fluid in the vicinity of the couplings? Any signs of fluid under the clutch pedal? Signs of fluid from the slave or from sticking your finger in the inspection hold and swabbing the inside of the cover?

There's only one thing you can adjust - the pre-load on the master cylinder piston (at least that is the case with S4+ systems.)

You are welcome.


No option code to tell you one way or the other? Or did you do the move-one-rear-wheel test?

This is not good.

I suspect you have a roller, bearing, bushing or something not quite right on the tensioner rollers. You're going to have to track it down ASAP. Chirp-chirp is not good.

EDIT: On the clutch - one other thing: pilot bearing?

FlyingDog

I do not have 220 listed on the code sheet over the gas tank. I did the turn one wheel test. I guess I have to get some new gear oil because all I have is 75W90NS. Gee darn, $30 to get my free LSD to work right. Although, if it's like everything else, it won't work right.

The 1/8 wide path the TB is taking is right in the middle of the cam sprockets, so everything seems to be lined up correctly. All of the bearings seem to be running true (obviously I can't see the lower idlers). The cam and oil pump sprockets are also running true. The only things I can think of is the brand new WP or the crank sprocket guide washers. I could try loosening the belt and repositioning it straight, then see if it starts the odd tracking again.

The car is on jack stands so I couldn't tell if the clutch pick up point was the same. I did buy a new pilot bearing last time I ordered parts since I thought that would be a cheap and easy fix for what I thought was wrong. After doing some reading of old threads I thought the throwout bearing matched the timing of the noises better. Like I said before, I really don't know much about clutches so I could be completely wrong.

The hose that is coming apart is the one from the body to the engine. On the engine end, it is peeling back an outer layer. The bracket on that end isn't mounted to the oil pan like it should be. I'll have to drop the starter to fix that because it is in the way of repositioning the hard line on that end. I was thinking of adjusting the preload on the master. There is a very short amount of take up at the top of the clutch travel, an inch or less probably.

worf928

How are you able to observe this? (I'm curious - not challenging. Since it possible to remove and replace the center belt cover without removing the pulley and balancer I wonder if it is possible to run a 928 engine with the center cover off.)

Waterpumps do sometimes arrive DOA in the box.

The washer between the sprocket and the sprocket-to-cam bolt?

True. But, can your Mark I eyeball do better than 1/8"? I would think that the belt should 'self-center' if all is well.

The wobble is, I think, not the first thing to worry about. It's the chirp-chirp. Have you rotated the crank by hand with the left and right belt covers off and had a look-see at the rollers? Also, the pre-S4 water pumps have that bolt that goes all the way through. Jim B., sometime ago, cautioned that that bolt is sometimes not replaced during a rebuild and can, due to corrosion from the coolant, bend at the threads and thus allow the main roller to sag.

Chirp-chirp could certainly be the waterpump.

You might want to start a new thread about the belt issues. Since this thread has clutch in the title you're not drawing the collective Rennlist post-timing-belt 'hit team.' (Only me and I don't consider myself part of that group as I've never had any post-t-belt issues.)

OK. If the clutch pickup point required an increasing amount of movement from the slave's piston then that might be a sign of something other than the bushing or pilot bearing. I've never encountered a situation where an air bubble caused the clutch to 'half-work.' Air bubbles seem to be a clutch works or pedal-snaps-to-the-floor deal.

This has no doubt contributed to the deterioration of the hose. In addition to the bracket there is a clip on each end of the hose that prevents the hose from banging around.