poor disengagement

[belize1334]

I'm having issues with clutch disengagement. I *think* I know the problem but I'm hoping someone will tell me that I'm crazy because I don't want to drop the transmission in the middle of winter. Let me know what you think.

It started happening as the weather got colder and then a few weeks ago my slave cylinder blew out. I replaced it, bled the system, and everything seemed fine. Pedal feel is great and the clutch fork shows good movement.

Unfortunately, I'm still getting clutch drag. I'm thinking the blown slave was a coincidence - brought on by extreme cold but not related to the current problem. It only happens when shifting from neutral into gear. If I start in gear (say put it in first and then start the car with the clutch in) I can shift between gears no problem. I can idle the car indefinitely with the clutch in and then when I ask for a gear it's effortless. Engagement is a few inches of the floor and nice and positive. No sign of clutch drag.

BUT, if I put it in neutral, let the clutch out, put it in again, and then go for a gear - nothing. Serious block out, clutch drag, car lurches forward as the shifter pushes agains the synchros - all the classic signs.

My diagnosis - the hydraulic system is fine, the pressure plate is moving nicely, but the disk is remaining in contact with the flywheel. Does that seem possible? Could gunk on the input shaft keep the disk from sliding on the splines, holding it agains the flywheel? Would this be consistent with the onset of cold weather - making the lube on the input shaft tacky and keeping the disk from sliding? Would starting it in gear break the disk away from the flywheel, allowing it to spin freely until the next time the clutch is loaded? It's the only thing I can think of.

I'm happy to rebleed the system but the intermittence of the issue makes me think it won't help... I'm thinking the transmission is gonna have to come out and I'm not looking forward to it.

 

[prove_it]

Sounds like a possibility. Also the disc itself could be warped and the allowing a bit of contact.

How many miles are on the clutch? If you can park in a heated garage for a night, that could help isolate the cold weather being a factor. I would think if it was then once the engine is hot, clutch and input shaft would be up to warmer than ambient temps.

At the least, it wouldn't hurt anything (besides the wallet) to replace the trans fluid. /ubbthreads/images/graemlins/dunno.gif It's quick and easy attempt anyway.

 

[belize1334]

Yeah I agree that with the engine warm the input shaft should get warmed up too but this seems to have no dependence on engine temp. I can drive it for 2 hours and nothing changes. If I start in neutral, push the clutch in and look for a gear nothing. But if it's in gear, and I push the clutch in, I can easily get into another gear, even if I let it idle for a while first - so clearly it's not dragging in that situation. I wouldn't think that transmission fluid could cause an intermittent issue like that. Same with a warped disk - I would expect it to drag all the time or not at all. The fact that it ONLY drags going from neutral to a gear tells me that it has something to do with the disk not moving away from the flywheel unless something breaks it free. I.e. pushing the clutch in with the car in gear and then blipping the throttle, which forces the disk to spin independently of the flywheel.

I'll probably go ahead and bleed it again just to be safe and replace the transmission fluid too. But something tells me I'm gonna have to get into the bell housing to make any progress.

 

[pot]

Have you considered a dislodged spring on the pressure plate? A random thought from my current transmission rebuild debacle.

 

[89Mirageman]

Maybe the master cylinder needs to be adjusted a tiny bit to get a little more travel.

 

[belize1334]

I had a dislodged spring once. The clutch didn't disengage at all - that's not what this is. The master cylinder is already adjusted for max throw. As I said, the engagement point is like 3 inches off the floor so there's plenty of travel - I don't think that's the problem. And I can't see how that would cause an issue only when shifting out of neutral.

 

[89Mirageman]

I had something very similar to this on a 90 300ZXTT back in the day. If I started the car in gear with my foot on the clutch I could go to any gear I wanted with the engine running. If I started the car in neutral it wouldn't let me put it in any gear. We adjusted the pedal and it fixed it. Not saying this is your problem, just saying in my case it fixed the issue.

 

[dsmless]

I had the same problem when mines was manual, I had a friend help me bleed/adjust the pedal assy as per the you tube videos by jackstrans. And problem solved

 

[belize1334]

Ok so maybe it's a matter of getting a bit *more* room for the disk to find a space to float. I'll work on it... thanks for the input.

 

[prove_it]

At the very least, do all you can do to remedy this without pulling the trans first. That way you know you have to and it's not a waste to pull it.

 

[tektic]

I had a nissan that would loose pedal pressure every time it rained. It ended up being contaminated fluid.