NPS with stuck clutch

[LeishaShannon]

Hi All

I just got in the truck to take it for a quick spin around the block after having it sit in the same place for ~3 months while we built the camper and the clutch pedal won't depress with "normal" pressure. I gave it a bit of a push and the pedal made it to the floor but stayed there. I could manually lift the pedal back up. I jumped under the truck and had Leisha depress the peddle while I felt the hose near the slave cylinder and I could feel the pressure increase so it looks like a problem with the slave cylinder or inside the clutch itself? Any pointers on where to from here?

 

[gait]

you have my sympathy, just some thoughts,

could also now be the master cylinder - perhaps clutch wouldn't release and pushing hard burst master cylinder seals. What's the fluid in the reservoir doing?

what position is the lever that extends from the rod pushing out of slave cylinder to the clutch (inside bell housing). Does it look like the clutch is released or engaged? Any play in the rod out of slave cylinder when pedal up.

Once on an old Holden, parked next to beach for 3 months the clutch wouldn't release. Not recommended, we towed it slowly and forced it into gear. Clutch released with a "bang".

 

[LeishaShannon]

Thanks Julian. The reservoir looks full, I can't see any leaks around the master cylinder. A friend suggested idling the truck and dropping it into gear as I turned it off to see if it would unstick, however it appears that the clutch is stuck "in" as I can put it into gear and the truck doesn't go anywhere.

 

[Goldanfish]

Have you tried starting it in gear ,sometimes works to release it.

 

[gait]

I'm guessing "in" as in "disengaged".

Ouch.

Presumably unbolting slave cylinder will leave the lever into the bell housing in the "disengaged" position. Just my way of asking if the rod connecting slave and that lever has any play? If no then probably hydraulics, if yes then probably mechanical within release mechanism.

When hydraulics have been discounted it could be the clutch release bearing (throwout bearing in US) sticking on shaft, or "fingers" for spring sticking somehow.

A photo of slave cylinder and lever may allow someone with similar vehicle to "spot the difference".

I'm not an expert in clutches, hopefully some who know more than I around, its just how I go about problem solving.

 

[LeishaShannon]

Thanks Julian.

I unbolted the slave cylinder and the lever returned to what I think is the normal position so I'm thinking thats a good thing as it means its a hydraulic problem rather than mechanical inside the gearbox?

Now when the clutch pedal is depressed I can feel pressure in the line at the slave end, but the pedal is still stuck when released. If the pedal is manually lifted up I see/feel no movement at the slave end.

Could it be air in the lines ? Should I try bleeding the system?

 

[kerry]

Hmmm? I think two things bring the pedal back up: a spring in the cab and the pressure of the clutch pushing back on the hydraulic fluid. I suspect the clutch is sticking in for some reason and not putting pressure back on the slave cylinder to push the pedal back up. Did you clutch fork move back smoothly when you removed the slave cylinder?

 

[gait]

sorry, got distracted,

there should have been a lot of pressure from that lever (clutch fork). Impossible to move by hand.

I wouldn't be ready to discount a problem with the mechanical bit.

I'm trying to think of a way of testing whether clutch is now engaged without starting engine - haven't got past trying to move vehicle a couple of feet in gear.

I would replace the slave cylinder and see what happens to the pedal, can it be pushed down and what effect on the slave/lever.

Bleeding is worthwhile, if nothing else it will discount one possibility.

All a bit odd really - which isn't very reassuring.

 

[PKDreamers]

When you depress the clutch pedal can you get gears.?

If you can and the pedal stays to the floor it is more than likely mechanical problem.

If you can't and the pedal stays to he floor it should be more likely hydraulic .

You will not be able to depress the clutch by hand.

I would try a system bleed.

Is there a return spring on the clutch slave if so it could be off or missing?

.

 

[LeishaShannon]

Thanks for the replies.

There is a return spring on the clutch slave, its not strong enough to pull the push rod back into the closed position. If I release the bleed screw on the slave should I be able to push the pushrod back into closed position? Perhaps with a clamp? As its fully extended now I can't get it mounted back on to the housing. Tomorrow i'll also try starting in gear to see if the clutch is engaged or not.

 

[kerry]

Clutch springs in the pressure plate should be pushing back on that clutch fork so the spring on the push rod doesn't do much work. If the clutch fork is not coming back to the engaged position, there's something funky inside the bell housing. If you open the bleeder you should be able to push the rod back in but it should also go back in without a huge amount of effort with the bleeder closed since it's just pushing hydraulic fluid back up into the master cylinder.

 

[gait]

nice to have something positive. Pointing to hydraulics.

Yes. Releasing bleed screw should allow slave to be pushed back in. It should be possible to push it back in easily, the fluid should flow through the master cylinder (if pedal up) into the reservoir.

If it goes in "smoothly" (whatever that means but any resistance or unenvenness may be felt) it possibly means the master cylinder needs a bit of investigating. Or the pedal bushing / spring / anything else that can make it stick.

The pedal has to be up enough to have the master cylinder uncover the port that allows the fluid into the reservoir, so that there's no residual pressure in the line when the pedal is up. So that there's no pressure on the clutch release bearing (like "riding" the clutch).

Just my thoughts, not enough to draw a conclusion yet, always possible to be "wrong".

 

[LeishaShannon]

I can't push the rod back into the slave cylinder. Releasing the bleed valve made no difference. I pulled the boot off and copped a mouthful of dirt/rust so I'm thinking its seized ? I'll order a new slave.
I also started the truck while in gear and sure enough it lunged forward so the clutch is definitely "engaged" now. However after starting the truck the pedal now goes straight to the floor with no resistance at all. This was not the case before starting the truck, I'm not sure what would have caused this?
I'm glad this happened in the front yard and not in the middle of nowhere, its been good being able to take the time to learn more about the mechanical/hydraulic side of the truck, I'm a complete newbie to this stuff.

 

[gait]

it should move easily with bleed valve open. New slave sounds like a good move, flush a bit of fluid through pipes before fitting new one. Aim would be to replace all fluid, don't recycle.

May also need new master. My understanding from description is pedal was initially stuck then went to floor after big push (before slave removal). If slave is seized then fluid from master must have gone somewhere, probably/possibly around the seal.

I would probably take the master out and have a look.

Probably also wise to bleed brakes some time, the fluid absorbs water and is possibly similar age to clutch fluid (my canter even has same reservoir). I've sent myself a note!

Learn as much as you can. The key is information. And when you've learned about everything the thing that will go wrong is the thing you didn't learn about ---- a re-expression of Murphy's Law.

 

[LeishaShannon]

Thanks Julian. New slave is on its way, I'll pickup some fluids and inspect the master this weekend.