What the heck happened to my clutch? It was crap, then self-healed.
 

http://ecomodder.com/forum/attachmen...1&d=1520006865

The clutch in my winter beater 2000 Metro has always been annoying garbage ... until it apparently "self-healed" this week.

Note: it shouldn't be worn out. The previous owner replaced it in 2013, about 25k kms ago.

Symptoms prior to this week:

• An exceedingly thin friction point that made it very challenging to engage smoothly, (but it could be done with more concentration than normal)

• Sometimes noisy (vaguely rattly) in gear or out, clutch up or down

• Loud squeal from the friction surfaces when slipping it aggressively from a stop

Then this week, I took off from a stop more aggressively than usual (on a hill, too) and it squealed like a stuck pig (which I expected). Probably the hardest launch I've done to the car.

Demon be gone!

At the next stop, as I pushed in the clutch to go into 1st gear, there was a distinct "clank!" and a brief rattling, as if something had fallen off something else and bounced around inside a metal case.

Immediately following that, the clutch has worked normally! Normal friction point, much quieter, no more mystery rattles. And it squeals much less when slipping aggressively.

Any ideas what was wrong before? I've never done any clutch work in my life. But I'm guessing maybe something was lodged in the clutch disc, caught either between the flywheel or the pressure plate... screwing things up, until it flew out. Does that make any sense?

Hmm.

Doesn't explain your self-heal, unless it finally knocked it completely loose and out of the clutch somehow...but I pulled the trans to replace the clutch on one of my cars and found one of the springs (I assume they are there to avoid chatter and/or absorb drive-line vibrations) on the clutch disk had a coil or so broken off. It was stuck in there. Different symptoms though...clutch would NOT disengage. Figure it was jammed in there, stopping things from working properly. Maybe you've just dislodged a spring that was broken and messing things up.

I'm wondering if maybe the flywheel and friction material needed to be bedded in? I can't explain the clanking though.

Last time I had a clutch clank, it was because the idiots who had replaced my clutch apparently used an air ratchet to drive down the flywheel bolts...they sheared and my flywheel suddenly found itself no longer connected to the engine.

^ whoops!

I had been talking about this earlier with Tim, and the idea of busted damper springs came up. It might have explained the noises.

I wonder if a loose part of a coil was the culprit, jammed somewhere on the clutch surface. That would explain the messed up friction point and excessive squealing.

Whatever it is, I bet it's sitting in the bottom of the transaxle bell housing right now. The mystery will have to wait until I swap transmissions... I have an extra one from a Swift 1.3 SOHC with the tallest 3.52 final drive.

I'm pretty sure there's a little cover/inspection plate at the bottom of the bellhousing. Just 4x 10mm bolts, irrc...if something came loose, you can probably get it out now.

We had some shaking/studder in the yaris versos clutch. Whole car would shake when taking off in 1st gear.
That also vanished with time :D works just fine now.

The clutch probably wasn't broken in properly, and the flywheel had glazed over. It's a common problem that's often fixed by a hard clutch dump. Same thing happens to brakes as well.

Would glaze have caused the clutch to be noisy when engaged and driving along? It was definitely transmitting some vibrations before.

Maybe I should do some more hard launches!

It's hard to tell exactly what the issue was without inspection or having seen/heard it beforehand. Glazing would explain what you describe though, especially if the installer didn't properly clean the mating surfaces.

Friction is energy trying to transfer and some of it is spent as heat, some as sound. It would make sense if there was inadequate friction that there would be a very short action of engagement and noise while slipping.

Hope it keeps on working for you!

I'm going with something to do with the pressure plate or throwout bearing.

There is virtually zero clearance between the clutch disk and the mating surfaces on either side of it when the clutch is disengaged; disengagement merely allows the clutch plate to spin freely between them. Something lodging in there and rattling when the clutch is engaged is pretty much impossible.

OTOH something lodging in a dumb place in the pressure plate is definitely possible, and could definitely mess with clutch actuation in a variety of ways.

One "aggressive" start would have been enough to de-glaze it?

(I put it in quotes, because it was probably a normal start for a lot of drivers.)

plot thickens... friction point thins
 

wdb, you just reminded me of one other (rare) symptom when the clutch was acting like garbage:

Sometimes (maybe half a dozen times) the razor thin friction point would move.

Meaning, I usually found it when the pedal was a couple of inches off the floor, but every once in a while, it would surprise me because it was right near the floor. Screws with muscle memory!

That support your theory too?

A "broken" finger (or two) on the diaphragm?

Right, that kind of thing. Or a stray bolt or one that backed itself out. Could also affect the actuation point.

Then again, hmmm. How about a loose friction pad that finally fell all the way out.

Good news:

I drove the car again today -- first time in about a week -- and the clutch is still acting in its new, normal way. Somehow it seems even quieter than before. (Probably my imagination.) But a pleasant surprise.

The car is 75% less annoying to drive!

Probably a bad or malinstalled throw out bearing.

Absolutely. You will get clutch chatter, squeaking, inconsistent clutch engagement, and general 'rough' clutch feel.

Yes. You are essentially knocking the glaze off of the clutch.

Seems tough to explain loud clanking with clutch glazing, I think. I like the idea of searching through the underside clutch/flywheel cover. I'd suggest a check sooner rather than later so you are more likely to find a small object before it possibly slips out a crack. My Civic's underside service-check cover is not an absolute tight fit. Little spring bits may already have dropped through.

I don't think there's an inspection panel/cover on this transmission.

Though I will admit I only looked at images of the gearbox online, and didn't look under the car.

Had a dual mass flywheel blow out the springs on a used diesel beetle that was very difficult to shift. Pieces were grenadine the throw out bearing arm.

Imagine a concentric tube around the flywheel with weights attached to long springs to help with NVH. The springs would deteriorate and shatter. DMF are bad for failing like that.