Sudden slipping clutch

[dobryan]

No need to double clutch except maybe in very cold weather when starting out until the trans warms up some.
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Dave O
'87 Westy w/ 2002 Subaru EJ25 and Peloquin TBD

"To travel hopefully is a better thing than to arrive." Robert Louis Stevenson

MD>Canada>AK>WA>OR>CA>AZ>UT>WY>SD
https://www.thesamba.com/vw/forum/viewtopic.php?t=620646

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https://www.thesamba.com/vw/forum/viewtopic.php?t=746794

[old_man]

[Abscate]

There is a natural tendency to associate failures with recent activity.

If the clutch disc was not contaminated with oil or brake fluid, it is just a worn out clutch.

Things that commonly get done incorrectly on a clutch job, other than cheap parts:

Cheap parts
Not resurfacing the flywheel in three places
Flywheel inspection
Pilot bushing
Cheap parts
Checking that disc slides cleanly in splines
Fingers on PP
Release bearing inspection
Cheap parts
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.ssS!

[jeremypbeasley]

Hey folks,

We're back on the road! New clutch, new slave cylinder, new master cylinder, all new fluid.

When I flushed out the hydraulic lines, there was a ton of greenish black crap in there that looked like mold and rust combined. I'm sure this wasn't helping!

Test drove it for 30 mins tonight without issue. There's definitely a big different in how sensitive the clutch is. Maybe this whole time I was driving on a shit clutch and just didn't realize it was as bad as it was. Definitely learning a ton here.

I'm also looking into "double clutching" as a way to better operate.

Appreciate all your help and support.

[E1]

Once all's good, you shouldn't have to do a clutch for quite a long time.

Ours on our first bus chattered a fair bit upon purchase. I was able to (carefully) "burn" the glaze off and it went over 40,000 trouble-free miles before replacement. And I only replaced it because the tranny was getting rebuilt.

I know some/most think downshifting by using "engine braking" is fine, but really it's "clutch braking" and it ain't fine. Brake pads are cheap, and good technique is free.
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‘84 Westy, 2.1L with Digijet, 5.43 R+P, GT Gears
"Adding power makes you faster on the straights.
Subtracting weight makes you faster everywhere."
— Colin Chapman

[jeremypbeasley]

Whoops. I missed the whole second one of replies. Catching up...

[jeremypbeasley]

Right on. Appreciate all the great points and examples.

Flywheel came back resurfaced today. I’m gonna flush out those clutch hydraulic lines real good before installing the new master and slave. Since I’m in here, I might as well replace the felt seal, rubber seal, and pilot bearing. Loads of fun when you’re working on the street in the winter.

In lieu of a clear silver bullet, I’m going to acknowledge that there’s a huge margin for my own error here and do some research to clearly know I can sense if/when clutch slips slightly in the future. I’ve only been driving a Vanagon for a year so it’s entirely possible that there was slippage before and I didn’t notice. I don’t recal any stink any any time.

Hoping when I put this all back together, I can get this puppy running till next summer without having to pull the damn gearbox off again!

Who knows, maybe I’ll be lucky enough to even have time for some body work!

[MarkWard]

Sodo, Then my vote is "Coincidence".
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[E1]

As I've said, this is a very intriguing case.

But if there's one thing I read on Samba over and over, it's claims of coincidental parts failures. I may not be a mechanic, but odds of such things are *extremely* remote.

I hope the result of this thread is definitive. Quite a mystery to be solved.
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‘84 Westy, 2.1L with Digijet, 5.43 R+P, GT Gears
"Adding power makes you faster on the straights.
Subtracting weight makes you faster everywhere."
— Colin Chapman

[Sodo]

[MarkWard]

I'll emphasize this again. You did a major panic stop prior to the clutch starting to slip. The brakes must have stuck partially on and that caused the clutch to burn up.

I worked for Audi in the mid 80s with the run away 5000. "The harder I pressed the brake pedal, the faster the car went".

It was determined the new owners, especially short women backing up, would get their feet mixed up, believing they were on the brake pedal not the accel pedal. Audi had so much bad press, they let it go. The recall was to add a shift lock to train owners how to "find" the brake pedal. There was nothing wrong with the car other than the brake pedal was close to the accel pedal to make room for the clutch pedal.

Anyhow I mention this because the brake are about 3x as powerful as the engine. There is no way the engine can overpower the brakes. I would suggest you examine your brakes very closely. It could be either the front or rear hanging up. In normal application, you may not notice this. It may need the "extra force" to cause this to happen.

If it's not the brakes as I suggest. It is just a coincidence that it happened after a panic stop and unrelated to the failure.
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[vwwestyman]

Kinda along Wildthings' idea, I am wondering if the clutch had been slipping off and on for some time, but had gone largely unnoticed?

For example, I had an old Cabriolet that had a slipping clutch. It would mostly only happen if I were to try to power up a particularly steep hill. I let off and it would quit slipping. But frequently the slippage could be minimal and perhaps not be noticed if things catch up with themselves pretty quickly.

Another time, with a different Cabriolet, I had decided to change the clutch for one reason or another. I drove to my friend's house in Wichita (two hours away) and we changed the clutch with a part he'd gotten locally. Everything seemed fine, but when I was about halfway home, going up a steep hill on the interstate, the brand new clutch gave out. It was slipping so badly the car couldn't go up that hill and I had to get a tow. I swapped in a new one at home and all was fine.

So sometimes stuff is just bad off the shelf.

One other thought I just had is, you might want to really flush out the hydraulic lines before replacing the slave cylinder. There could be some kind of crud in there that was preventing the fluid from returning fully, which would show up as being like you were halfway pushing the pedal. (I don't recall, on a Vanagon are there rubber lines in the system? If so, I'd get a new one-they can fail internally.)
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Dave Cook

President, Wild Westerner Club

1978 Champagne Edition Westy, repowered to '97 Jetta TDI
1973 Wild Westerner
My Thing

[Wildthings]

[E1]

Right attitude, good. 👍🏼

Per the sudden braking, did you bring it to a complete stop? In gear? Clutch in or out? Did it stall?

It's okay if you're not sure, recording such details in one's memory aren't exactly priority compared to safety considerations "in the moment."

Intriguing issue all-around...
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‘84 Westy, 2.1L with Digijet, 5.43 R+P, GT Gears
"Adding power makes you faster on the straights.
Subtracting weight makes you faster everywhere."
— Colin Chapman

[jeremypbeasley]

For the record, I’m entirely open to this being improper driving/operating. Damage is done. I would just want to know what I’d need to do differently.

I drove five miles home at about 20mph immediately following the heavy braking incident. I stopped 3 times along the way just to let it rest. Once home, a week later, I drove it around the block just once. Maybe I’m ignorant, but could I really fry a disc as bad as I’ve shown in under 6 miles of driving?

Besides what I’ve described just now, what would be improper use?

PS, I don’t think there’s any malfunction in the cross shaft. It appears to operate flawlessly despite its age.

[E1]

Kinda did mention improper use.

Any downshifting without matching revs is improper technique, as would be stopping in gear without dumping the clutch at some point.

Just didn't want to come off as accusing the driver.
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‘84 Westy, 2.1L with Digijet, 5.43 R+P, GT Gears
"Adding power makes you faster on the straights.
Subtracting weight makes you faster everywhere."
— Colin Chapman

[Sodo]

Clutches are not damaged on the low end of the torque curve.

That clutch is burned up from slippage while the engine is turning fast and putting out max torque..

It could look like that from either a malfunction such as a stuck cross-shaft bushing, or improper use (which you have not mentioned).

I saw some van-folks at Descend on Bend trying to tow-start a diesel van.
At some point, the tow-van clutch belched out a thick puff of smoke.
His disc looks like yours (like a piece of carpet) but he didn't know it (yet) because he didn't take it out and look.
But when we left Descend on Bend his van was still there, almost the last one in the camp.
Poor guy had a California license plate... (600 miles?)
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'90 Westy EJ25, 2Peloquins, 3knobs, pressure-oiled GT mainshaft, filtered, cooled gearbox
'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered gearbox
....KTMs, GasGas, SPOT mtb

[E1]

I'm curious if during your panic stop the engine went so low in revs as to stall with the clutch engaged -- and/or too much was demanded of the parts while working the clutch.

Just a thought. I've mentioned heel-and-toeing here several times but have yet to get a reply from others knowing or using this (and Mark Ward surely does).

Also, the pressure plate seems to have a chunk of clutch on it as if ground off by a ton of stress. It looks very similar to a clutch drum after toasting a clutch on a small race motor when caused by heat and/or chatter.

Glad you nailed it regardless.
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‘84 Westy, 2.1L with Digijet, 5.43 R+P, GT Gears
"Adding power makes you faster on the straights.
Subtracting weight makes you faster everywhere."
— Colin Chapman

[jeremypbeasley]

Thanks for checking in on me, folks.

Today was the first day in a month I’ve had to work on the van. I pulled the transmission off shortly after the original post. I also removed the master and space completely. I have since received my replacement master and slave cylinders. Even if they’re not the culprit, I figured I’d replace them once and for all.

Today I removed the pressure plate and disc from the flywheel. They’re toast. Photos below. I also removed the flywheel and dropped it off for resurfacing.

Thankfully I’ve got a brand new SACHS clutch kit in the garage that I can throw on, but I remain perplexed as to how this happened.

I’m don’t really care about finding the mystery as if it’s some map on the back of the Declaration of Independence. However, I can only assume this will happen again if something is left in the same way that caused this in the first place.

Checking boxes: The wheels spin freely and I have no reason to believe the brakes have ever seized to the point that it would overwork the engine. The flywheel end play is just above spec at .006”, but that shouldn’t be a big deal. Everything’s been torqued to spec.

The only suspect thing here is the leaky master cyclometer. However that doesn’t explain a slipping clutch at all.

Any help would be much appreciated. I really need this van back up and running again for a trip with the kiddos soon.

Lastly a comparison between the disc I just pulled and a brand new one, just for kicks.

[Wildthings]

I am going to guess that for some reason when you did your panic stop you got lubricant all over your clutch, either engine oil or tranny fluid. Can't ever remember hearing of this happening before though.