Bleeding clutch

[red vtec]

just rebuilt the slave cylinder, how much fluid should I need to put through to bleed it, it's taking a lot.

Chris

[neill1607]

I changed the master & slave, so the system was completely drained.

I can't have used more than about 1/4 litre in total to refill & bleed.

is that 250ml?

Edited March 5, 2011 by Neill1607

[red vtec]

oh

[andydclements]

That reads like an "Oh. I've gone through a lot more than that already".

Are you still getting air coming through?

[red vtec]

yep, i've put a fare bit through already

[andydclements]

If it is still pulling air, make sure it's all out first by removing the slave cylinder from the bell-housing and raising it in the air as far as you can (leave pipe connected) then bleed it being careful to not push the piston out (g clamp or similar to keep it in).

If you are still getting air then either you're unlucky enough to have a faulty new slave cylinder or the seals in the master have gone also.

Edited March 5, 2011 by andydclements

[red vtec]

Hi Andy,

I have new seals for the master but was hopeing that the ones in there are ok as I cannot see fluid in the car, although I did have oily residue under the passanger seat would this be the master??

The slave cylinder looked like it was missing a complete seal! as it only had the metal clip and the rubber boot on it, but the kit I got had another seal with it.

Chris

[andydclements]

can't see how clutch fluid from the master would get under either seat unless it was a virtual river of fluid inside the car. I assume when you put the seal in that's shaped like a cup you put it in the way so that it's bit of a pig to get in (bit that flares out goes in the cylinder first).

If all else is right then you'll have to suspect master seals.

[GavinT]

I just had the same problem with mine. Couldn't stop getting air bubbles. In the end I removed the master and bench bleed it to see what was going on. Sure enough I kept getting bubbles. There was no sign of fluid leaking but I was getting air. So a seal had gone somewhere. I ordered a new master which I have not yet installed so can't be 100% sure that was the fix to the problem. I was told many moons ago that to forget rebuild kits and just install new cylinders and do both together. If you are having issues with one it is likely the other one will start giving you problems soon.

[red vtec]

Andy,

Yep I have put the seal in correctly from what you are saying (I didn't know)

Gavin, I'll do the master seals as well, I've got them so I'll change em out.

Chris

[fsrowsell]

Chris, I just changed out my master as will. I was getting air in the system, but it was not leaking! I would assume the lotus position and push the peddle by hand and would hear sucking noise.

[red vtec]

Hi Felix

I could hear something bubbling! so sounds like I need to the master cylinder as well.

Chris

[fsrowsell]

I would say yes, Chris

[GavinT]

Exactly what I got with my master. Every time the pedal was released I got air bubbles in the reservoir.

[red vtec]

Cheers Guys, looks like it will give me something to do.

[rogerch]

I've read through the above and saw no mention of what I'm about to say, so forgive me if I missed it.

The slave cylinder is a problem because it's horizontal, air travels up in liquid, so the bleed nipple must always be at the top, so, is it ?

Second, I had trouble until I jacked the back of the car up, thereby ensuring the bleed nipple was at the uppermost point of the cylinder.

If all else fails you can take the cylinder off, hydraulic hose still attached, hold it upright with the bleed nipple open, lower than the master cylinder and allow it to gravity bleed. When the air is gone tighten the bleed nipple and refit it.

[red vtec]

Hi Roger,

The bleed nipple is at the top, the car is also jacked up I have put a lot of fluid through so I'm wondering if air is being pulled in?

I've left the car jacked up do you think it could just be air in the cylinder?

Chris

[rogerch]

If you have only touched the slave cylinder, and there was no prior fluid loss, if air is getting in it can only be on the pipe/slave cylinder union.

There are many technicians for purging air, you can get someone to help, pump up pressure on the pedal and then release the bleed nipple (messy suggest collection tube) this blasts everything under pressure, and can catch an unwary air bubble.

Or as suggested by Stevem at Avoca, leave the pipe attached but remove the cylinder, hold it lower than the master cylinder undo the bleed nipple and allow gravity to do the work.

On all of this restating the obvious, keep an eye on the level in the master cylinder, if it goes too low, you will get air in the system and have to start again.

All this is assuming you have put the rubbers in the right way round, compression should expand them and push to the outer walls.

Good luck.

[Bibs]

Or as suggested by Stevem at Avoca, leave the pipe attached but remove the cylinder, hold it lower than the master cylinder undo the bleed nipple and allow gravity to do the work.

Bubbles don't usually care much for gravity. Quiet the opposite in fact. Just allowing it to drain to pull fluid through will give the bubbles a chance to avoid being purged which is why the fluid needs to be forced through.

[rogerch]

Gravity Bleeding

It works, I can vouch for it, used it, done it, known technique.

[dodge1979]

My two peneth worth..slave cylinders have always been a bugger to me. Its already been mentioned that seal kits are pointless really, the reason being that we are talking about a cylinder bore that is ten plus years old..or even far greater and as such any new seal wont seal fully as the cylinder bore will be worn..no matter how low mileage of lack of use etc...its just a fact. Recon ones arent worth bothering with either...again new seals in a worn bore. Always fit new..at the end of the day theyre not that expensive and have a guarentee!

On a note of bleeding....I found the same problems with my T-series engined vittesse....the only way to bleed it properly was the clamp the slave cylinder fully closed so it could not move at all...then let the fluid gravity fill first..then proceed with the same method as brakes...assistant required or one of those pressure bleeders....although Ive found sometimes they can be too harsh and actually blow the new seals...so I use an assistant...cheers Dad this was the only way to make sure no air gets in the system....

Darren

[stevem]

If you jack the car up at the rear it actually increases the chances of air being trapped in the back of the slave cylinder, as the part that traps air goes higher and the bleed nipple goes lower ( on my 88 Esprit anyway ). I had endless trouble with mine until, as Roger has mentioned, I took the bolts out of the slave and let it dangle down with the nipple at the top. Only 2 bubbles of trapped air popped out but that's all it took to fix the problem. If you are getting air entering the system elsewhere, this won't fix anytjhing but when you come to bleed the system it's a sure way of getting those last trapped bubbles out. The diagram below shows the area where the air gets trapped in red, that part of the slave cylinder sits lightly higher than the nipple when bolted to the car.

[Vulcan Grey]

I've only had luck bleeding the clutch when I hung the slave like this.

If left mounted in the car, it seemed like the air couldn't get to the bleed for some reason.

[red vtec]

Thanks for all the replies I will have another look at it soon, unfortunetly I'm away this weekend.

Chris

[Rich H]

I ended up using my oil sucker to suck fluid throught he bleed nipple.

I think the problem was that air in the MC just gets pumped back and fore in the pipe as it's so long.

So either you pump gallons of fluid through in an attempt to purge it all, jack up the rear as high as you can and let the bubbles rise to the SC or dangle the SC and let the air gather in the MC.

Also remember that the initial turn of the pipe from the MC is upwards so air will also gather there and take an age to purge...

Pressure bleeder and lots of fluid would be the easiest but it'll still waste a lot of fluid. Mind you it's not worth using SRF it's not exactly working hard at high temps!