Clutch problem

[webbslinger]

Has anyone ever experienced a clutch master cylinder tha gave the symptoms of air in the lines? I have been struggling with a clutch that goes to the floor on the first couple of pumps. After pumping up it works fine but almost immediately after letting it out the peddle is slack again until it gets a couple more pumps. It was working fine before the engine was pulled.
So this sounds like air, but I pulled the slave and filled it, pumped the peddle 150 times a bunch of times, rigged up stand pipes on both the bleed vent and the line, all of those things. Beginning to wonder.
I will keep at it, but in the meantime I'm curious if there could be a problem with the MC? I can't figure what could be wrong with it that would make it mimic air? Does anyone have direct experience with a MC that did this?

[StressCraxx]

What type of hose do you have? If the hose collapsed internally, or it expands from the pressure, it might give you the symptoms you describe. If it's the red plastic hose from a Cortina, it will melt if its too close to the exhaust.

[el-saturn]

........i had the same problem AND the perfect MC got a new seal set, fitted it twice (a lovely area for working and cussing, isn't it?) - still showed those symtoms, so got a new one ------- finally i lent one of those dot4 pressure tanks (i can't remember the english term!!??) and after "investing" 100ml of dot4 (that's the amount which bleeded thru the lines) it was perfect. i was glad to have realised that you can't really bleed yr hydraulics alone!! greetings from appenzell (yes, where they make some real nice cheese!!) sandy

[Chancer]

Do you have the slave cylinder upside down?

Maybe it is not possible on the elan but on many similar set ups it is easy to make the mistake.

The fluid pipe must enter the cylinder at the bottom and the bleed nipple must be at the top.

Unless you turn the car upside down but that gets messy

Editted, yes I do have direct experience of fitting a cylider upside down, it was exactly as you describe, over the years I have helped many people who have done the same thing by accidentally swapping brake calipers from right to left, human nature being what it is after spending weeks bleeding they are often quite angry (through frustration) to have the problem resolved for them

[Maulden7]

I also experienced exactly this problem a few years ago. Changing the seal in the slave cylinder appeared to have sorted it, but after a short while the issue returned, so I changed the slave for a good quality new one & everything's been fine ever since (beware the Chinese copies sold on ebay)

This may have something to do with the proximity of the exhaust to the slave cylinder (especially if you have a large bore exhaust system) This heats up the metal of the cylinder & also affects the seal itself so I wrapped the cylinder in heat reflecting material, easy to do & seems to work.

A mate had a theory that the seal was turning itself inside out & then returning to the correct position after a few pumps? Certainly the clutch always came back after a few pushes on the pedal, but the whole thing was a little disconcerting on the road.

Dave M.

[prezoom]

Speaking of bleeding the clutch slave cylinder, the first time I pulled the engine and gearbox, I went through the nose bleed of trying to get the air out of the system.

In attempt to solve the problem, I took a piece of round stock about 3/4" long and welded a flange with a 1/4" hole that aligns with the flange/hole on the slave that the return spring attaches. My slave is connected to the master cylinder with an AN-4 line, which makes it completely removable from the bell housing. By using an appropriate length 1/4" bolt and nut, I can insert the round portion in the slave, the bolt goes through the hole in the flange and then through the hole in the slave. The nut goes on the end of the bolt. This allows the piston in the slave to move towards the end of the slave, but keeps it captivated, preventing the loss of fluid.

Now the slave can be moved anywhere the AN line will allow, which means it can be raised up with the bleed screw at the highest point. It doesn't take purple neck effort to depress the clutch pedal to expel the air. Just enough effort to move the fluid from the master cylinder to the slave. I also use a Speedy Bleeder, so there is no need to do the "up/loosen/down/tighten" routine. Just pump until the air is no longer present in the loop of the hose to the bleed bottle. No more of the afore mentioned nose bleed.

It also allows me to remove the clutch slave from the bell housing and install the piston blocking mechanism at the time I remove the engine and transmission. This keeps everything in tact, with no need to re-bleed after re-installing the slave.

[mbell]

My latest trick to finish bleeding the slave cylinder is to use a vacuum bleeder (on a speed bleeder) with the pedal wedged down.

My theory for this is, with the pedal down the system is sealed from the master. The vacuum pulls the air from the system easier than the fluid. So the remaining air is expelled from the system and the system is refilled with fluid when the pedal is lifted.

Seems to have worked in my car, but it had a stuck clutch player at the time do wasn't sure if it was already bleed or not.

[Grizzly]

Do you have any form of Heat insulation round the hose/slave cylinder where it gets close to the Exhaust manifold? i know my clutch went very wooly when i had been for a run.

As for bleeding it, first off check there is no fluid coming from the master (don't know if you have a +2 or 2 seater but have a good look where the master bolts to the peddle box area) next crawl under and flick the rubber of the front of the slave and check for fluid leakage (as above the bleeder should be in the top position), next have a helper push the peddle down while you hold the flex (see if it expands in your hand). If that's all good get a nice tight fitting piece of pipe to catch the fluid from the bleeder (its better if its clear, and have it going to a bottle of some sort). You need a helper to pump the peddle three times and on the third time hold it to the floor while you open and shut the bleeder quickly while watching the fluid coming out for bubbles, do that three of four times and you will be good. (obviously keep an eye on the fluid level so you don't run it out)

If you are using a Vac bleeder or Speed bleeders make sure you remove the Bleed nipple and put liberal amounts of grease on the threads when you screw it back in or the Speed bleeder will just draw air down the threads and the Vac bleeder will never stop pulling bubbles (makes you think there is some thing wrong)

[jk952]

Assuming seals etc. are good, don't forget the age old: dangle the slave on a wire (tubes connected) full of fluid overnight with the bleed screw up, then bleed the next morning. I suspect excessive pumping of the pedal creates very fine air bubbles that take a while to dissipate (or is that better said precipipate, out of the fluid to a larger air bubble?). Worked for me in 1969 on an old TR4 and much later again on the various Loti
Jack

[seniorchristo]

I've had good success with the Mighty Vac for one man brake bleeding.
http://www.amazon.com/Mityvac-MV8000-Au ... ke+bleeder

[Robbie693]

If all else fails, wedge the pedal down overnight with a piece of wood or something and the system will bleed itself

Robbie

[webbslinger]

Thanks all. I've bled it successfully numerous times following your suggestions but I think the trouble is some seal in there has failed. I'm going to rebuild the slave and mc and when they go back in I'm going to prefill the slave, use speed bleeder screws, remote bleed line, my vacume brake bleeder, etc. The hydraulic line is new. Thanks for all your advice, it will be working soon.