Baffled by an ongoing problem with my 2010 Sigma car (Ford box, hydraulic clutch) and hoping for advice as I've not had anything similar with any hydraulic clutched car before. Sorry for the long tale!
Last summer I had Sevens and Classics upgrade the car with a lightened flywheel as part of the 140bhp Supersport upgrade. Set off round France and did about 1500 miles, as we got back to London I had a slight issue getting gears and had to pump the clutch a couple of times. Used the car a few more times before lockdown 2 hit and had no problems.
Had to press the car back into use to visit my parents in North Wales a month ago. Coming off the motorway near their place the clutch pedal is dead and I can only get a gear with a lot of pumping. Can't even get a gear to move the car the following day. No apparent loss of fluid but the reservoir is full of black goo, presumably from a seal that has broken up.
Borrow my Dad's car for the trip down to London and bring back a second-hand low miles spare master cylinder that I got off a club member who had upgraded. Fit it and bleed it out on my parents drive, works fine.
Drive back to London with no problem at all until I get to the North Circular and again, can't get a gear. Limp back with much pedal pumping and rev matching.
I have to be back in Wales, so S&C collect the car for a service and to sort the clutch fault. Diagnosis is that it needed bleeding and they test it thoroughly before dropping it back.
Off to Wales again last week, same thing, clutch pressure lost as I come off the motorway. Pumps up again and is manageable for the rest of the trip (took the scenic route this time) although the biting point varies a lot.
Drive back to London last night. Clutch fine for two hours of twisty Welsh mountain roads, but coming off the motorway and again I can't get a gear, lots and lots of pumping and rev-matching required to get it back without wrecking the gearbox.
I've never known clutches to lose pressure like this when there is no load on them - it's almost like it is temperature-related. I'm wondering if the flexi is getting too hot, or that there is an issue with the clearance or positioning of the concentric slave cylinder - maybe it is touching and heating up the bearing on long runs?!? I know that fitting a second-hand master means that one might just be duff as well, but the fact it usually only fails after a couple of hours of motorway is strange.
Anyone got any ideas? Obviously the answer is replace both cylinders with new but with the engine needing to come out that's going to be a big bill and I want to be sure there isn't some other underlying cause or I'll end up with the same issue.
PS I know it sounds as though I am happily joyriding round Wales during lockdown, but I am having to travel there to provide urgent care for my parents and need to leave the sensible car with the missus. I will admit to enjoying taking the scenic route rather than the motorway as a small bit of joy in an otherwise bleak time!