clutch postmortem

[jasapp]

I'd been enjoying my S52 swap for at least two weeks before I started having shifting trouble. I'm kind of at a loss as to what happened, so I'll just try to start from the beginning and hope one of you guys can figure it out. I opted to keep the transmission that originally came on my e30, a euro with the early style pedestal shifter mount.

I bought my clutch off ebay from a seller named ultra_drift, his account has curiously been closed. His auction had one of those "Make Offer", so naturally I low balled him. I forget what I paid exactly, but I think it was about 2/3rds of his asking price. This might have been my first mistake.

When I installed the new clutch, I put the friction plate the same direction the old friction plate was facing. I also had the flywheel turned down quite a bit, but I don't have an exact weight. Everything else was done according to the Bentley, including the correct torque for attaching the clutch to the flywheel.

After I installed the engine, I had to modify the pedestal a bit to fit in the right location. I also made a little adapter to hold the back of the pedestal to the car, since the little rubber donut thing fell off the second day of driving the car. At this point, I noticed the car shifted fine while the engine was not running, but was tricky to shift if the engine was running. I attributed this to the hacked up pedestal mount.

A month or two went by while I fixed a few other things on the car. Every now and then, I'd take a spirited drive around the block. I had trouble shifting into reverse and first gear. I bled the clutch, and that seemed to help some, but not enough. Eventually, I ended up replacing the slave, master, and all of the hydraulic lines. I'm not sure if that really fixed anything or not, but I kept driving it.

About a week later, I noticed the clutch had started slipping at high rpms. Before too long, that turned into slipping at low rpms, and I started hearing metallic crunching sounds every now and then. It sounded like the car was driving through a small pile of metal leaves. Shifting into gears became harder and harder, and the clutch started slipping badly enough the car was unusable. At this point, I parked the car in my garage.

I pulled the transmission out tonight, and wasn't too surprised to find the clutch in bad shape. When I first separated the transmission, bits of metal, pins, and a bolt fell out. Two of the bolts holding the clutch to the flywheel were missing, the rest were loose. The clutch was covered in gashes from the metal flying around, and the friction plate was badly glazed. When I pulled the clutch off, it actually came apart in two pieces. I'll include some pictures of this.

What did I do to cause this? Any ideas?

What should I do next? The flywheel didn't seem to have any cuts or scratches, can I just clean things up and install a new clutch?

Is the pedestal causing the shifting issues, or was it the clutch all along?

[7pilot]

The pressure plate failed.
Was it used?
Do you remember torquing the pressure plate mounting bolts?

m

[jasapp]

The pressure plate was brand new, from ultra_drift on ebay. I did torque all the bolts correctly according to the bentley.

[flyboyx]

yikes! definitely, the p-plate came unglued on you. man....i will be pissed if that happens to mine. let me go through my old emails to see if i can find their phone number. i had a problem where they sent me the wrong one so i had to converse with them over the phone a couple of times.

did you reuse the old bolts that came with the previous clutch? i hate to say this, but it sounds to me like they came loose on you at some point during use. perhaps i think it is possible that caused your p-plate to come apart? anyway, when i put mine together, i used red locktite on all my bolts, planning not to have to take it apart any time soon. besides, it isn't so strong that you can't unscrew the fasteners if you apply a little extra torque.

your fly is probably fine if you don't see any visible damage.

if you think about it, post up a photo of your clutch disk.

[Uber E30]

did you reuse the old bolts that came with the previous clutch?

This is my guess

[jasapp]

I did use the old bolts, although I did put blue loctite on them during assembly. I'm not sure if the pressure plate broke, and that caused the bolts to back out, or if it was the other way around.

I just found their number on the receipt for the clutch. I get a message saying to call back during business hours, even though they should be open according to the hours in the message. I'll keep trying.

Here are pictures of the friction disk.

[lennon]

I think your mistake was reusing those bolts.

[RickSloan]

your mistake is a loose crank bolt.

my roomate went thru 4 pressure plates before we located the problem. Go outside and i bet you can move the crank bolt by hand.

[5KWattson]

reused crank and PP bolts twice now and never a problem as long as tehy are in good shape. wouldh ave replaced them but dealer was out of stock and the company we get parts through at work didnt have any nor would have any for a week.

but i think the major weak point was the PP

[jasapp]

I checked the crankshaft bolt and it isn't loose at all.

The bentley says the flywheel to pressure plate bolts are only held on with 18ft-lbs. That isn't enough to deform them, so that shouldn't have been the problem.

The ebay pressure plate of dubious nature is my guess. I've ordered a new pressure plate and friction disk from Ireland, and all the associated bolts from pelican. The flywheel looks ok, there are a few nicks and scratches but none on the surface for the friction disk. I'm a little concerned about the threads in the flywheel being enlarged by the loose bolts. I'm going to think about it for a few days before I take it to a machine shop.

Thanks for everyone's help.

~jeff

[JGood]

reused crank and PP bolts twice now and never a problem as long as tehy are in good shape

What do you mean good shape? They are stretch bolts. When properly installed, they stretch a predetermined amount. When removed, they are still stretched. When you attempt to reinstall them, they will not clamp to the same force, and can stretch further, and loosen easier (or even break). I don't know how you'd know that they are in good shape by looking at them.


OP, used flywheels are cheap. Just get another and have it resurfaced/turned down.

[jlevie]

Flywheel and pressure plate bolts are not torque-to-yield (stretch) bolts as evidenced by a torque number rather than an initial torque and angle. While best practice is to use new bolts, reusing the bolts usually works okay. In this case I'd say that the cause of the failure was a substandard pressure plate.

[JGood]

Flywheel and pressure plate bolts are not torque-to-yield (stretch) bolts as evidenced by a torque number rather than an initial torque and angle. While best practice is to use new bolts, reusing the bolts usually works okay. In this case I'd say that the cause of the failure was a substandard pressure plate.

I stand corrected. I always heard/read that they were stretch bolts. I guess that makes sense, with no degree numbers given in the manuals.

Either way, for such a cheap part, I always replace them (along with flywheel bolts).

[etxxz]

^^^ +1
i've reused those Pressure plate bolts in the past... actually used one set three times untill they were in such bad shape (stripped head) that i had trouble removing them.

My guess is that you didnt tighten those bolts. Atleast not correctly. That interface is a hardstop, metal to metal on metal so no matter the quality of the pressure plate components (springs), if these bolts were loose, they were never tightened to begin with. Vibration wouldn't have undone ALL of them, specially not having used locktite. This was probably what caused your clutch to fail. I didnt use a torque wrench on mine, i just tightener those fuckers using a 6" extension on my allen wrench untill i could no more.

[Spaz]

^^^^^ +2

I've reused pp Bolts and Flywheel bolts numerous times. As long as you have a thread sealnt/locktite on the flywheel bolts they'll be fine. And locktite on the Pressure Plate bolts. (I typically replace these since the allen head strips fairly easily and i rather not have to end up dealing with stripped ones.

Looks like a failed PP to me...best of luck getting it resolved!
-Cam