has anyone else had this weird hydraulic clutch issue?

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paul_w
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has anyone else had this weird hydraulic clutch issue?

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.

Cheers,

Paul

 

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!

KelvinH
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Not just me then!

Had exactly the same problem after i bought my 620s privately.

Clutch worked perfectly for about 10 miles then progressively failed until the pedal went flat to the floor.

After parking up for about half an hour and letting the car cool down, the clutch started working again ... and then progressively got worse as the car heated up. After bleeding the system there was a slight improvement but the problem continued.

Like you i thought it was heat related as the removable pedal box cover was getting very hot, so i covered it in heat reflective tape. This resulted in an improvement but after letting the car stand for a couple of weeks the pedal was progressively getting softer.

I eventually solved the problem by replacing the clutch fluid master cylinder cap and the problem was fixed, It was probably a problem with the seal - so maybe it was an issue with overheating that resulted in a damaged seal.

Anyway three years later and the problem has not returned. As a side note: covering the pedal box cover with heat reflective tape greatly reduced the heat transfer into the cab.

Hope this helps

paul_w
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Hmm, thanks Kelvin. If the cap fixed it I wonder if the breather was blocked, the seal just stops spillage, but if there was no breather it could feasibly cause issues. Will check mine Scratchchin

AnkerB-S
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I had the same issue. New master cylinder fixed it!

Anker Berg-Sonne
Stow, Massachusetts

Old fart pretending that age is just a number

1987 Caterham Super 7 1700 Supersprint
2004 Porsche Boxster S
2009 Mercedes CLK 350 Cabriolet

paul_w
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It's odd that the second master cylinder I tried has the same issue straight away though, when I know it was a good one - on what car did you have your problem on Anker? Your Supersprint is a cable clutch right?

Andrew Gilbert
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My issue was similar, I'll recount the tale in case it helps although the issue was different (sort off)

Mine is/was a c20xe 16v vauxhall unit, converted to dry sump and hydraulic clutch, when cold it was fine, when hot progressive clutch slip, back to the guys who built it, re-bled the system, check things over, all OK for the first 40 mins of driving then slipping again.

That new clutch lasted a shade over 2200 miles, back again and only thing to do was to have it all apart to have a look, out came the box, clutch worn down to the rivets, all seals were OK and release bearing was still brand new looking, it was thought the clutch had been mismatched with the flywheel, so we changed that for a lightened item (any reason for an upgrade) together with another clutch. This time it was OK but after 200 miles the problem returned, The only thing we hadn't changed was the master cylinder (it was a brand new item) and talking to a chap who runs a c20xe competitively and who also works on a lot of agricultural equipment said "its the MC, I've seen this on a number of items, when its getting hot the m/cylinder seal is preventing the fluid to return which gradually applies pressure which then results in clutch slip" (or something like that, it was 4 years ago). So a new MS was bought and bingo, problem gone.....

It may help..

Love a HPC

1992 HPC vx2.0 c20xe goodness....

https://www.facebook.com/groups/caterham7c20xevariants

7 wonders of th...
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Some of the Girling caps had no breather, I bought new ones with a plastic deflector and a decent breather, you can also get a bellow to permit expansion without fluid loss or moisture ingress.

https://www.burtonpower.com/girling-moisture-barrier-integral-master-cylinders-gir64478356.html

Basically a smaller version of the one used on the AP race master, I also use a Girling cap on the AP as the threads are deeper and I found the AP version could pop over the final thread as you tighten it.

7 wonders of th...
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Also seen a car where the volume of fluid expanded with the thermal transfer and discharged via the breather hole, this then dripped down onto the brake and clutch pedals - which made them a tad slippy !!

7 wonders of th...
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the bellow for the small reservoir (44mm OD) is the one on page 7 ironically.....

https://www.earls.com.au/old-catalogue/files/497f86ffbb862-RESERVOIRCATALOGUE2009.pdf

I did have a link to a UK supplier but this is no longer working so I've mailed Girling and will repost when I receive a reply

timb2117
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Ahhhh that explains it! Different car same hydraulic clutch, kept getting the odd leak from master cylinder and also really foul discolouration in fluid bled, checked, bled, checked blah blah, converted to cable as advised on forum, (thanks guys) lighter, simpler, fixed.

But heat certainly explains it very well.

AnkerB-S
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Mine has a hydraulic clutch. Exactly the same issue. Gradual loss of clutch when warming up, pumping would work, dirty fluid.

Anker Berg-Sonne
Stow, Massachusetts

Old fart pretending that age is just a number

1987 Caterham Super 7 1700 Supersprint
2004 Porsche Boxster S
2009 Mercedes CLK 350 Cabriolet