Clutch hydraulics mystery

[The Veg]

I love a good mystery!

...Well, except when it comes to why my car does annoying things.

I've had the Plus 2 basically operable for about 120 miles now. Along the way to getting it operable, I rebuilt the entire clutch-hydraulic system: rebuilt master, new slave, new stainless-braided line between them, and I added a remote-bleed line that follows the main line back up the firewall. I also made a sheet metal heat-shield for the slave based on an ancient post here, and put a silicone heat-shielding sleeve on the remote-bleed line. Nothing has been leaking in that 120 miles.

Despite that seeming good health, I've had issues with the functioning of the system from the beginning. Sometimes it would act as if there was air in the system, requiring a few pumps of the pedal to get any action- but only SOMETIMES. I also noticed that if I 'rode' the clutch- keeping my foot on the pedal just enough to stay right at the beginning of the resistance- it worked every time.

Today I opened everything up and investigated. I found only one thing that seemed amiss: the fluid in the reservoir, which remember was only used for 120 miles, looked black. Taken out of the reservoir so some light can pass through it, it was more like dark grey and not fully opaque, but it's still worrying. The insides of both cylinders still look nice and smooth and shiny and I can't feel anything rough inside, at least as far as I can get my smallest finger inside. The seals all still look new.

So now I'm scratching my head. My first thought is put it all back together and bleed it and see what happens, but as my questions always say, is there something I'm missing here?

[h20hamelan]

Yes, bleed away
It is merely residual from seals

[1owner69Elan]

Veg:

Not sure this is pertinent to your clutch problem but I experienced ongoing and mysterious problems with my clutch a few years back. Basically, after bleeding, the clutch would be fine but later it would start acting up. Below is a post of my trials and tribulations. Bottom line: I found that the slave cylinder seals are not all equal, in material or shape, or consistently functional. Even in the case of using a brand-new slave with its new seal. My problems went away with a proper seal:

viewtopic.php?f=37&t=2052&p=295548&hilit=+slave+seal#p295548

[nmauduit]

not sure it's relevant in your specific case : I've had a similar hydraulic behavior (though on the brake, tandem Girling), occasional pedal to the floor and would require pre pumping to get the brake 100% operating when the curve would come (was testing on a track). This was due to rubber residue preventing the return valve to fully close, residue I believe coming from a "professionnal" rebuild that ended up forcing the seal without proper lubrication and tearing off a rubber hair which ended up traveling with the fluid for occasional valve leak (could have been the rubber was bad, though I'm using Dot5 silicone which is not corrosive). The problem came back some time later (couple years, that is maybe 20 hours of use), and massive bench purging (1l) while checking what came out with a filter solved the issue. For now...

[baileyman]

Gary Anderson suggested I crack open the nut from the main to the secondary that is on top of the main and look for a bubble. Dang if at least one big bubble came out, well after several bleedings. Patient all better now. John

[Sploder90]

Just a thought... Check the circlip on the clutch slave cylinder... Mine was held in just by the return spring ..

[Elan45]

I have found in past that the design of the slave cylinder, w/ both inlet and bleed ports arranged in a horizontal pattern so that if the cylinder is mounted to the bell housing, the top half of the cylinder may be full of air. So, I release the cylinder from the BH so that the bleed port can be oriented to the top and can then be voided of air. When doing this procedure, you must be careful to push with less pressure so as to not pop the piston out of the cylinder. It doesn't take much pressure at all to rid the cylinder of air, in fact I often stroke the pedal by hand. Reassemble the cylinder to the BH and you should have the best clutch feel you've ever experienced in your Elan.

RL

[fatboyoz]

Hi 1owner,
Could you please share with us the vendor of the seals that cured your clutch slave problem?
Regards,
Colin.



quote="1owner69Elan"]Veg:

Not sure this is pertinent to your clutch problem but I experienced ongoing and mysterious problems with my clutch a few years back. Basically, after bleeding, the clutch would be fine but later it would start acting up. Below is a post of my trials and tribulations. Bottom line: I found that the slave cylinder seals are not all equal, in material or shape, or consistently functional. Even in the case of using a brand-new slave with its new seal. My problems went away with a proper seal:

viewtopic.php?f=37&t=2052&p=295548&hilit=+slave+seal#p295548[/quote]

[1owner69Elan]

TTR’s slave kit, represented as “real” Girling, solved my flaky clutch problem.

[derek uk]

Previous info : viewtopic.php?f=37&t=14659

[The Veg]

Update:

I took RL's advice to get the slave vertical for bleeding, this after removing everything from the car and opening both cylinders to check the seals (both still look fine).

I built a simple tool to make sure the piston didn't come out of the slave, just a long bolt with two nuts and a strip of stiff steel with two holes in it, one for the long bolt and one for a short screw that protrudes into the piston to make sure that this piston-retainer can't slip off under pressure. The long bolt also goes through the hole for the return spring. The slave dangled down so it was vertical and air can come back up the remote-bleed line that I fitted a while back.

A few strokes of the pedal got all the air out, but then it stuck again: pedal returns and then when pressed again is only pushing against its spring rather than any load. Hmmmmm. Remembering that there is a spring inside the master which should make it return, I pulled the master again and worked it by hand a few times. The piston definitely sticks now and then, despite a new seal and a smooth-looking bore. Bloody hell. I wonder if the problem is some loss of smoothness of the bore at a microscopic level that is diffict to see. Not wanting to go down any rabbit-holes with it, I ordered a new master.

[bitsobrits]

A careful measurement of the MC bore and piston diameters could be helpful to diagnose the issue. If the piston to bore clearance is too great the piston can cock in the bore enough to cause a bit of stiction. Also can be caused by the piston being too short, i.e. a pattern item from a rebuild kit.

If the piston is cocking, it usually leaves faint witness marks in the bore.

[2cams70]

Have the seals been fitted the correct way around on the piston? ie the taper leading toward the piston and not the other way around?

[The Veg]

Yes, right way round.

[2cams70]

What type of clutch pipe are you using? Hopefully not one of those waste of money braided types when the standard nylon one is perfectly suited to the job. There's no guarantee that the rubber used in those braided types is compatible with brake fluid in the longer term. The rubber needs to be a specific type for brake fluid compatibility. If the rubber is not of the correct type the hose may have swelled internally restricting the fluid flow and leading to the symptoms you describe.