Clutch

[Loon]

Has anyone heard of a clutch failing once getting to temp and then sitting/cooling and works fine?  

My 95 slipped a little then just would drive.  Went into all gears but no pull.  Off the trailer today and it drove as it should with smooth shifts and we drove it 5 miles or so.  

[Slartibartfast]

New one on me. My first thought is heat soak (exhaust leak cooking the clutch hydraulics?) but I would expect that to prevent disengaging the clutch, not make it slip.

 

Does yours still have the clutch damper? I've heard of those acting up. Haven't had to mess with one, given mine's got the slushbox.

[gamellott]

Ya, that's a new one on me unless you have a leak in your master cylinder where it is letting in air past the piston as you drive and progressively gets worse. But that would be a bit different symptom I think.

 

I'm not aware of a damper in the system. The couple of these that I have owned have included a Master Cylinder, Hose, and Slave Cylinder. Don't judge me, that's what they're called...

[Slartibartfast]

CL-9 in the '95 manual shows the damper. Looking at the diagram, it's even simpler than I had assumed it was! I thought it was supposed to slow engagement if you pop the clutch, but it looks like it's just adding a little squish to the system. NVH thing? Probably unrelated to this issue, unless it's gone all to pieces inside and the debris was blocking the line back to the master.

 

Now that I'm thinking about it, I've heard of rubber brake hoses failing like a check valve, so you can apply the brake, but it won't release. I haven't heard of a clutch hose doing that, but it sure does sound like what yours was doing.

 

1 hour ago, gamellott said:

Don't judge me, that's what they're called...

 

Ackshually the manual calls it an "Operating Cylinder," but, yeah, nobody else does. I've only ever seen/heard it called a slave cylinder.

[gamellott]

6 hours ago, Slartibartfast said:

CL-9 in the '95 manual shows the damper. Looking at the diagram, it's even simpler than I had assumed it was! I thought it was supposed to slow engagement if you pop the clutch, but it looks like it's just adding a little squish to the system. NVH thing? Probably unrelated to this issue, unless it's gone all to pieces inside and the debris was blocking the line back to the master.

 

Now that I'm thinking about it, I've heard of rubber brake hoses failing like a check valve, so you can apply the brake, but it won't release. I haven't heard of a clutch hose doing that, but it sure does sound like what yours was doing.

 

 

Ackshually the manual calls it an "Operating Cylinder," but, yeah, nobody else does. I've only ever seen/heard it called a slave cylinder.

Never seen a damper, but... Oh well, something to be aware of, Kind of like a Pontiac 301 Turbo. I've only seen one in the wild in 5 years of working Auto Parts in the hayday when they were popular.

 

Hoses acting like a check valve does happen. I failed to remember that one... It's a part to consider.

[Aonghus]

TLDR - try gravity bleeding at the slave cylinder.

 

So we had similar symptoms. Recently replaced the clutch and all the goodies on my son's 93XE. Here's the two scenarios we experienced.

 

The old clutch was decidedly bad, easily slipped when trying to accelerate or pull a hill. We didn't drive it much in this condition but when it was cold in the morning it would have some decent grip.

 

Replaced the clutch, put everything back together, no grab, couldn't even back out of the shop. But it was 2am by then so we came back to it the next weekend. My buddy had a hunch that the hydraulics had built some pressure while it was disassembled and it was holding static pressure against the fork. He was right! Gravity bled the hydraulics at the slave cylinder, golden.

 

Which makes me think, had we thought to try bleeding the system when he bought the rig (we were told the clutch was bad) we may have got some life out of the old clutch. I believe if there's a bubble in the system it reacts to increased heat with just enough pressure against the fork to cause some slippage.

[Loon]

8 hours ago, Aonghus said:

TLDR - try gravity bleeding at the slave cylinder.

 

So we had similar symptoms. Recently replaced the clutch and all the goodies on my son's 93XE. Here's the two scenarios we experienced.

 

The old clutch was decidedly bad, easily slipped when trying to accelerate or pull a hill. We didn't drive it much in this condition but when it was cold in the morning it would have some decent grip.

 

Replaced the clutch, put everything back together, no grab, couldn't even back out of the shop. But it was 2am by then so we came back to it the next weekend. My buddy had a hunch that the hydraulics had built some pressure while it was disassembled and it was holding static pressure against the fork. He was right! Gravity bled the hydraulics at the slave cylinder, golden.

 

Which makes me think, had we thought to try bleeding the system when he bought the rig (we were told the clutch was bad) we may have got some life out of the old clutch. I believe if there's a bubble in the system it reacts to increased heat with just enough pressure against the fork to cause some slippage.

Perfect.  Waiting on a open slot in my buddies shop(with lift) to replace the clutch and will definitely heed your advice.

 

Thanks man

[Aonghus]

Sure thing, hope it helps. 

If you have a minute and the weather is cooperating with you, the bleeder nipple on the slave cylinder is pretty easy to get to.

 

Pop the lid off the master cylinder, crack the bleeder and let some fluid drain out. Have someone watch the master cylinder reservoir so you don't let it all out and suck air in! Then top it off again and see if it helps. That was seriously the fix for us.