Mrmerlin

is it possible that one of the line fittings to the MC or slave are not tight?
The reason i am mentioning the MC piston length is that the new replacement MC parts are in reality defective , as they are not manufactured to the original specs
It has been suggested that the engineering portion of the production company made a mistake on the design specs of the new parts.
What this means is that the new part must be taken apart and modified to give the longest possible piston stroke.
That said if you cut off to much from the new piston then the rear seal on the MC will go past the fluid feed port and then cause fluid to escape from the rear of the MC.

Mrmerlin

Colin I was also wondering if the new goodrich line may be defective, or might have gotten crimped, this might cause a situation where the line will work but when say it gets hot or is moved a certain way it wont let the fluid return and thus possible suck air from the rear side of the MC when the pedal is released

danglerb

+1 thats the only place where the fluid doesn't always have positive pressure or near it.

Lizard928

Interesting thought.
However the line is of very high quality, and worked fine for many months without incident. Before it left after replacing the slave there was not one mark on it at all.
I also know that all the metal connections, being hard line into slave, hard line to flex line, flex line to hard line, and hard line to master are all properly tight and are dry.

I like the thought of the fluid not being able to return and that allowing air back into the system. But thinking about it I doubt that would be the case. I say this because the helper spring on the pedal forces the pedal down, overcoming the weak spring inside the unit. This means that it requires the pressure from the slave unit to be able to force the pedal up. I hope that makes sence.

And I do know about the stop length rod being different. And as I said I took both the internals (origonal unit in the car) and the new one, they were the same length. And when bled works perfectly.

I found out from one of our local fellows that there is a grease called rubber grease which is compatible with brake system componants. So I am going to use some of that to seal the top of the MC after bleeding it to see how it goes.



But if there are any more ideas as to where to look, keep em comin.

Lizard928

Ok, just got an update on this.

He went out and moved the pedal up and down a few times slowly, and rapidly. Not much movement, just through the spongy spot and the air pocket moved out and back into the resevior bringing the pedal back to proper firmness. Now the clutch disengages fully again and he can get into all gears with no issues.
I am having him put some rubber grease (thanks Terry) packed into the top of the MC so if the problem comes back we will know it isnt from the MC seals.

Baffeling for sure though

Mrmerlin

is it possible that the push rod is not correctly adjusted? IE try loosening it up one turn so the push rod jiggles a bit when the pedal is released

GlenL

I was just thinking this, too. Maybe there's a small leak and the system isn't re-filling itself.

I used the later adjustment method with some preload and found I needed the slop to uncover the fill ports.

Lizard928

I tried the adjuster rod previously with no preload, and with preload and had the same issues.

I left it with no real preload. Just touching when the pedal was released. The opening/release port is open to the resevior in its current adjustment.

Fabio421

You didn't happen to replace the resevior did you? The nipple to feed the clutch master isn't drilled when new and you have to drill it when installing it in a 5 speed car. This happened to a local lister and the fluid in the rest of the system allowed him to bleed the system and operate the clutch for awhile but then degraded over time.

I know it's a farfetched idea but I thought I'd throw it out there. At this point, anything is possible.

Lizard928

Resevior was not replaced, and I ensured that the hole was free of obsructions too.

Hilton

Colin, did you ever figure this one out?

My 89 has an issue with the clutch going soft and dragging, or in some cases, not disengaging at all. It would go away after being parked, or sometimes when driving home (whilst carefully rev-matching.. damn I hate red stop lights when clutch is not working).

A fluid change and bleed, and its been fine for a few months, and is back again now. No leaks evident. The only thing I could think of to explain the symptoms was heat soak possibly related to my x-pipe, but a look under there last night shows the hard line and flex line are both clear of the manifold and x-pipe.

A search turned up this thread, so I figured I'd see.

Luckily my '87 is back on the road, so is now my DD until my 89 has all new suspension, brakes and a happy clutch. I figure I'll change out the slave (have a couple of spares in boxes), and use a master cylinder seal kit, while the '89 is off the road, but knowing what conclusions you came to would be valuable.

Hilton.

SharkSkin

Hilton, how old is the rubber hose in the circuit? The later cars have a jacket over the lower hose at least; there are good reasons to have that jacket but if the line is about to burst it could be ballooning under the jacket and you won't know until it lets go. Hydraulic lines tend to fail near the crimp, so if it were me I would pull the jacket back from either end and inspect. If you see any sign of cracking/deterioration of the pressure hose, replace it.

Lizard928

Hilton,

I am guessing you managed to get the car through emissions testing then?

As to the problem, yes I did end up figuring it out.

The problem was the throw out bearing. It was stuck/dragging on the guide tube. this was preventing the hydrualic circuit from fully retracting. The second thing that caused it was too much preload on the assistance spring. Backed off the spring and replaced the clutch and the problem disappeared and has not come back.

Hilton

Thanks Dave, I'll check it out. As far as I know its original, so I'll add the rubber section to the list of bits for my next order - the strong Aussie dollar is making orders happen thick and fast

However I'd expect a ballooning problem to be consistent - my clutch dragging only happens sometimes, seems to be usually just after pulling away from a hot start (e.g. hardware store car park), or very occasionally when sitting in very slow stop-go traffic.

The fact that it goes away after I've been moving a while, or never happens after cold-start in the morning, indicates to me its heat-soak related, or possibly a temporary air intake thats rising to the reservoir. Fluid level is unchanged.

Thanks Colin - I'll check the spring's preload, in case its causing a slight drag and causing friction. Congratulations on finding that - sounds like a hard one to explain.

My whole clutch is only 2 years old - and the problem only appeared a few months ago, so I'm inclined to think its elsewhere than the clutch internals. I'll start a new thread with it - might be time to do a direct comparison between the routing of my 87's clutch hydralics versus th 89's in case I'm missing something obvious.

The 87 sailed through emissions testing - was actually surprised the guy drive the car out so soon, but as he said, its very quick when the car passes first time Since then its had full intake refresh, upgraded LH/EZK chips for diagnostics, timing belt tensioned, all fluids/filters and various minor electrical things (like tension warning light repaired!), and it's good enough to let my wife drive without worrying

Ok, I'll go investigate and see what I can figure out is different between the two cars. Thanks for the update