Clutch woes.

[supercass]

Started the car to drive it out of the garage after working away as a key worker for many months. No movement on clutch pedal. Further pressure resulted in a noise which seemed to come from the bulkhead and then there was full and immediate movement but the pedal was sloppy. Nothing like it should be. Examination of the master cylinder reservoir revealed what appeared to be a very low but not depleted fluid level but the fluid that could be seen was dire. It was black. I was pretty certain the master cylinder was at fault so I ordered a repair kit. Having taken out the master cylinder there seemed no way I could get the piston out, it would slide freely and smoothly but would not vacate the bore. I cut my losses and ordered a replacement master cylinder which thanks to the excellent services of Robsport arrived the very next day. Within an hour of it arriving further idle manipulation of the old master cylinder resulted in the piston vacating the bore!!! I primed the new master cylinder as far as I was able before fitting but fully expected that the system would by now be full of air and that the spongy pedal would persist until I bled the system. This wasn't the case though, the pedal would only travel about one third of the normal travel and then would move no further. Slackening off the hydraulic pipe to the master cylinder resulted in fluid escaping as expected and I was able to press the pedal all the way down. Keeping the pedal in the down position and tightening the hydraulic pipe and then releasing the pedal resulted in the reservoir level dropping which I would expect, however the pedal would then again only travel about one third of the normal distance before coming to a stop. One answer would be that the slave cylinder has failed but given that there would be now be air in the system ( and in no way would I expect this to cause a hard pedal but I stand to be corrected) and that the problem with a hard pedal has only occurred after replacing the master cylinder this seems unlikely, hopefully. The other thing is that actually there didn't seem to be that much wrong with the old master cylinder, there was no obvious corrosion, pitting or scoring of the bores or piston and the seals seemed to be in remarkably good condition for the original items. There was some corrosion on the fork arm which wouldn't affect operation. I have to say I've never replaced a clutch master cylinder before, having driven more recently semi automatics, automatics or manuals with cable linkage but this seemed an easyish job for a novice like me (if fiddly, awkward and time consuming doing it in a confined space singlehandedly) so you will have to excuse me if I show my lack of knowledge.
An help and advice would be appreciated. supercass

[saabfast]

Two things spring to mind. One is the reasonably common problem of the clutch fork wearing through the pivot and jamming (or one heard of recently where one of the thrust bearing slipper blocks came out somehow), although I have not personally had these happen. The one I have had happen, which must be pretty rare, is a torque spring in the friction plate breaking out and jamming the clutch. It would be a lot nicer if it was something in the hydraulics as the 'box would not have to come out.

[FI Spyder]

I agree with Saabfast. Clutches aren't rocket science. Sounds like the transmission has to come out. While some take the engine/trans out the top that sounded like too much work for me (FI model) and I had previously purchased combo jack stands hydraulic jacks for $36 each. This gave me 20/21" of lift. I purchased an ATV scissor jack for $40 on sale, put that on a T shaped melamine board (so it could fit through the narrow stance of front jack stands, put it on small rollers, bolted the ATV to transmission through an adapter plate made from some metal lying around. The toughest part was the top bolts by the fire wall but after they where out, moving the trans back and lowering it in steps everything cleared, there a notch in the frame that allowed the top of bell housing to clear the frame and had access to the clutch with out taking out the engine etc. There was little wear in the fork so greased it and reused it. The plunger has an unexplained inset with rather sharp edge (all the better to gouge into the fork) so I ground this down a little. People who have had the plunger wear through the fork have reinforced the fork with a strap welded to the back side (once bitten, twice shy) but with grinding the plunger and lubing it, I think it likely won't happen again in their life time. If clutch is old now is the time to replace it, not "next" year. Mine "looked" good but it would judder at anything above idle. The new clutch solved the problem. Taking off any "sheen and emery cloth taking of sheen on flywheel may have worked too but I wasn't going to take the chance.

[busheytrader]

Over 30 years ago the pivot pin wore a hole in my clutch fork at around 65,000 miles IIRC. The pedal went down to the floor with no resistance, came back up and stuck solid. Luckily it happened just as I left my driveway. It prompted the V8 conversion as I had to remove the engine and gearbox out anyway.

I've probably replaced / rebuilt the master cylinder 3 times over the years. The seals seem to be more susceptible to perishing than the slave at the bottom. The original lasted 37 years. Before getting inside the bell housing it might be worth detaching the slave cylinder to check it's not the problem. The slave pushrod should stay put as you ease it away. Don't try pulling it or subjecting it to sideways pressure as the clip holding the other end to the clutch fork can be brittle and break easily.

[busheytrader]

I haven't had to bleed the hydraulic clutch system yet when rebuilding it. I've filled the reservoir in the master, left it overnight and any air has risen up the pipe and out through the top. Top up the reservoir again, the pedal is firm, drive a few miles and all is well. I was expecting to crawl under to bleed at the slave cylinder but never had to.

[supercass]

Stupid question but do you leave the reservoir cap off overnight, Busheytrader?
Theory via another forum (Sorry!) is that the clutch friction plate is stuck (the car has bee inactive for a while) and the old master cylinder seals were compromised when the cutch pedal was pressed, that the clutch friction plate is still stuck and the now initial sponginess is accounted for by air now in the system and the remaining lack of movement due to the stuck plate. Sounds quite plausible to me or am I clutching at straws? supercass

[Beans]

No put the cap back on, it is vented.
The cap will prevent contamination from getting in the reservoir.

[busheytrader]

As per learned Beans, keep the cap on.

Might be worth bleeding from the slave cylinder to clear a potential airlock. Hopefully your free movement is an airlock and not a clutch fork / plate problem. On the V8 bellhousing there's a removable bottom blanking plate to look inside it. I dont think the 2L version has That option.

I've never had the clutch plate stick to the flywheel on mine. There's plenty of posts on the net about freeing it off while driving on and off the gas pedal and clutch pedal, again I've never had to do that.

I hope you don't have to remove the gearbox to sort out your problem. As a key worker through the crisis you have my respect.

[saabfast]

I had the clutch stuck on the TR7 for the first time this year, probably because it has not been driven for ages due to the CV19 (had it a lot with an Imp many years ago for some reason). As it is parked on the drive facing the garage I started it in reverse with the clutch down and it broke away within a foot or so. Must remember to exercise it more often in future.

[Cobber]

My money is on the clutch fork impaling itself on the pivot ball!

[dursleyman]

When a clutch plate is stuck to the flywheel it feels normal but you just can't get gears with the engine running, so nothing at all like the symptoms described.
Be worth taking the slave off just to check but the problem sounds like it is going to require the gearbox off.

[supercass]

So to update. Have bled the slave cylinder, nothing seemed to come out out when I first removed the bleed nipple, but is now flowing. Had to start the car in gear (reverse) to get it out of my narrow garage. The clutch did go down once during this procedure and I thought it was resolved but no such luck it seems. Was able to do this and had access to bleed the slave cylinder but little else. Clutch still not going down (unless the slave cylinder nipple is open) and now when I started it (in first gear to move it there was no movement. It just gets worse it seems!! supercass

[busheytrader]

Unfortunately it sounds like the problem's inside the bell housing. I've had the rear brake slaves rust up and seize beneath the rubber boot a few times in 36 years, never the clutch slave.

If the slave's bolts are unscrewed by 15 - 20mm and the clutch pedal's depressed, the slave should push itself away from the housing if it hasn't seized up.