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strange clutch problem
rodgling - 15/5/13 at 09:02 AM

My clutch is slowly getting worse (creeps forward with my foot on the floor, hard to select a gear when stationary). Adjusting the throw of the master cylinder helped temporarily but now it's got worse again. The pedal feels softer too.

I've tried:

- blocking off the master cylinder and seeing if it goes solid (it does)
- replacing the slave
- bleeding it
- checked for leaks (there is a union for a clutch pressure switch on the clutch hose)

without improvement. Also I've had a look through where the slave mounts - it's hard to see much but the clutch fork appears to be retained by the spring clip, slides freely, etc, so everything in the bellhousing appears normal.

Ideas? I'm a bit stuck...

adithorp - 15/5/13 at 09:37 AM

Sounds like could be master cylinder seals. Is it OK when you first press it then starts to creep when held down?

britishtrident - 15/5/13 at 09:56 AM

Sounds like the recuperating seal/valve in the mastercylinder, when under low hydraulic pressure the fluid is seeping back to the reservoir, at higher pressure the recuperating seal seats properly and holds pressure.

rodgling - 15/5/13 at 09:59 AM

When I blocked off the master cylinder output, it was solid enough that the seat was flexing behind me as I pushed, with no sign of creep - so it seems to be holding way more force than is usually needed to operate the clutch. Is that enough to be sure that the master is definitely OK?

Not sure about the car taking a moment to start creeping forward - it's possible I guess.

adithorp - 15/5/13 at 10:08 AM

Pushing it hard (with pipe clamped/blocked) forces the seals out and they work. It'll let fluid seep past when the presure isn't as high. Try blocking it and just apply very light presure and see if it creeps down.

rodgling - 15/5/13 at 10:23 AM

Ah, that's very useful to know. Thanks, I will give this a try.

I have a spare m/c of almost the right size so I think whatever happens I will try replacing the m/c and see what happens, it's preferable to taking the engine out to look inside the bell housing!

britishtrident - 15/5/13 at 11:19 AM

quote:
Originally posted by rodgling
Ah, that's very useful to know. Thanks, I will give this a try.

I have a spare m/c of almost the right size so I think whatever happens I will try replacing the m/c and see what happens, it's preferable to taking the engine out to look inside the bell housing!


The problem is definitely not inside the bell housing or you would be losing fluid, a new set of seals in te master cylinder should fix it (also check the end of the internal spring in the master cylinder isn't broken), bigger bore master cylinder will give you more clutch clearance but make the pedal effort heavier.

snapper - 15/5/13 at 11:36 AM

I had a problem with the gearbox spigot hitting the back of the crank causing drag in the box
Difficulty engaging gears, drive to wheels with foot on clutch.
To check this I undid the bellhousing bolts and put washers in between 4 bolts did back up and the problem went away
I then made up a 2mm spacer between bellhousing and engine, split that in 2 and inserted 1/2 at a time
I did not have to split and remove engine and box

rodgling - 15/5/13 at 08:28 PM

Good news: replacing the master cylinder has fixed the problem, must be the seals not working at low pressure as you said. Cheers.

Chris_Xtreme - 15/5/13 at 09:52 PM

jammy timing for this post for me, as I reckon I am suffering the same problem. I'll have to get at that master cylinder.