has anyone else had this weird hydraulic clutch issue?

[paul_w]

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]

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]

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 

[AnkerB-S]

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

[paul_w]

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]

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..

[7 wonders of the world]

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 the world]

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 the world]

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]

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]

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

[John Vine]

Something very similar happened to me (R400D) when touring in France in 2015.  I lost all clutch action, and even pumping the pedal had no effect.  The problem was down to a failed m/c seal.  I replaced the m/c with a new one, and then refurbed the old one with a Girling kit to keep as a spare.  No problems since.

I would suggest you start by replacing your m/c with a brand-new item.  If that doesn't fix it, suspect the slave (although these are usually bomb-proof).

JV

[7 wonders of the world]

The genuine Girling cylinders are normally excellent - are all the ones above genuine or copy versions...? have they all got a functioning bleed hole in the cap too..?

[paul_w]

Thanks all - had two hour-long journeys in the car yesterday with no problems at all, so it does seem it takes a long motorway run to trigger. Fluid is looking increasingly dirty though. No drop in the fluid level.

Have checked the breather, no problem there. Both the master cylinders are the Caterham-fitted originals like this, the first one to fail was the car's original 20,000 miler, the one in now is a known good 5000 mile one from a car that was uprated at Premier Power that I got in a job lot of parts leftover from the upgrades. Wouldn't usually have fitted a second hand part but as I say I was stuck up in Wales and happened to have it.

I think the next step is to strip and inspect the one that came out and if the bore is good I'll kit it. I agree that sticking a new master on it makes sense, but having just dropped nearly £500 on a service and clutch diagnosis at S&C and with a suspicion that something is causing the cylinders to fail, I'm going to hold off spending another £80-100 right now. I'm not earning at the mo cause I'm looking after my folks.

The only other odd thing was that when I changed the first cylinder the fluid that came out was red (as well as being filthy) which I've not seen before - I know you can buy red fluid but I don't know if it is a different formulation - could mixing fluids have caused an issue with the seals maybe? 

 

[Jonathan Kay]

"The only other odd thing was that when I changed the first cylinder the fluid that came out was red (as well as being filthy) which I've not seen before - I know you can buy red fluid but I don't know if it is a different formulation - could mixing fluids have caused an issue with the seals maybe?"

 

Bright red, not just dirty brownish orange?

 

It could have been some sort of transmission fluid. That is reported to damage seals in braking systems.

 

Jonathan

[Geoff Brown]

Has the slave in the bell housing been considered as the culprit as that is where the maximum heat absorption will occur ?

May be a rogue slave. Red fluid indicates to me that ATF was inappropriately used.  

  

[paul_w]

hmm. It was bright red, just like ATF. I wondered if ATF had been used, but I am assuming that S&C will have disturbed and re-bled the clutch hydraulics when they did the flywheel swap and gearbox rebuild, and that would seem to be an unlikely error for someone with their reputation. Prior to that I had no issues with the clutch for 5000 miles after buying the car with 12k on the clock.

Had been discounting the slave as I figured I'd be losing fluid into the bell housing if the issue was at that end, which Tim at S&C concurred with. Plus of course I'm trying to avoid taking the engine out if I can help it!

[paul_w]

You can see the red colour in the fluid above, it's not that rusty orange that old fluid goes, sadly don't have a pic of the cleaner fluid that came out of the reservoir that was more clearly red with less black goo in it.

[John Vine]

AFAIK, red clutch fluid is used in some racing bikes.

Re #12, my loss of clutch action was due to a faulty valve seal:

 

 

This caused the fluid to leak back into the reservoir when I pressed the pedal.  The primary seal on the plunger was working OK.

JV

[7 wonders of the world]

This is interesting as the foot valve design is tried and tested and been around since Adam was a lad.... makes you wonder if theres been a manufacturing change or new component supplier.....

you could always try a different brand Tilton offer one with remote or mounted reservoir, as do AP, Willwood, Alcon etc

 

[7 wonders of the world]

Have you all been using the .7 master cyl...?

Are you running clutch stops...?