clutch bleeding

[john130]

I have fitted a new master cylinder & renewed the seals on the slave cylinder, along with a new 3 piece clutch using all lotus components. whatever I do I cannot get all the air out of the system. The bleed screw is higher than the inlet , and I have used a pressure bleeder and manually bled the system but still can only get a firm pedal by pumping. Any suggestions please!

[tower of strength]

Hi John,

try wedging the clutch down over night with a piece of wood between the pedal and the seat, in theory, the air will rise up into the reservoir!! Thats the theory (this worked for me on a Spitfire rebuild and was a last ditch attempt, prior to renewing everything again!) I find Vacuum bleeding using a Mityvac usually works first time.


hope this helps

Mark

[MintSprint]

...I find Vacuum bleeding using a Mityvac usually works first time.

A cheaper alternative to the Mityvac (or similar) is to simply buy an 8' or 10' length of clear pvc tube (eg. washer tube, from your local motor factor) of the right diameter to fit over the nipple. Simply suck the fluid through (being careful to stop before you get a mouthful of the stuff, 'cos it tastes nasty and is mildly poisonous!). Stop sucking and close the nipple when you can't see any more bubbles being drawn from the nipple.

If you use any form of vacuum bleeding, it sometimes helps to remove the bleed nipple altogether, first, and to smear the thread with a small amount of silicone grease to help seal it, otherwise it can be easy to draw air in past the thread of the nipple when you apply a vacuum.

If you wedge the pedal, as Mark suggests, to allow the bubbles to rise to the master cylinder, you may also find that it helps to remove the slave cylinder from the bellhousing and let it hang below the car, so that the bubbles have a nice, straight path back up to the M/cyl.

[tdafforn]

My method is to get a 6foot peice of tube, attach it to the blead nipple and route it back to the reservoir so that I can see some of it when I am sitting in the car.
Then I open the blead nipple and sit in the car and pump the pedal until bubbles no longet go past in the tubing. You'd be surprised how long it can take some times!!
Tim

[MintSprint]

My method is to get a 6 foot piece of tube, attach it to the bleed nipple and route it back to the reservoir so that I can see some of it when I am sitting in the car.
Then I open the bleed nipple and sit in the car and pump the pedal until bubbles no longer go past in the tubing. You'd be surprised how long it can take some times!!

Only problem with this (and the reason why I wouldn't be at all surprised how long it might take you!!) is that you are potentially pumping aerated fluid back into the resevoir! It can take ages for bubbles to 'settle out' of brake fluid!

[Matt]

I had problems getting my air out when I did mine just a few weeks ago, so I got my old Gunson ezblead out and it got the air out in less than 2 minutes !

[GrUmPyBoDgEr]

I don't use any fancy methods, just the one man under the car & another pumping the pedal.
What I have found to be very important is to ensure that the slave cylinder is rotated into a position so that the bleed nipple is at the highest point (12 o'clock). Car also nose up would be good.
Sounds a bit basic & I'm sorry if it offends but I have experienced that the slightest twist off this position will leave air in the cylinder.
John

[MintSprint]

Agreed, John - whatever method of bleeding you employ, orientation of the bleed nipple to avoid trapped pockets of air is going to be very important.

Personally, I've never had the slightest trouble bleeding Elan clutch hydraulics. I will happily use the two-man approach if there is a second man (or woman!) to be had, but quite often have done it single-handedly, so this wasn't an option.

Gunson EasiBleeds work well 99.9% of the time, but I've had 0.1% occurences where the seal at the master cylinder has failed, spraying brake fluid all over the paintwork as a result, so I prefer vaccuum bleeding techniques these days, just to be on the safe side, when I'm working on my own.

[john130]

thanks to everybody for their suggestions. I have realised I have connected the unions the wrong way on the slave cylinder! Perhaps I should explain that I have been doing a chassis change over a number of years, and the cylinder was overhauled when the engine and gearbox was out of the car. The clutch is not 100% free of air, but enough to get the car back on the road for the dreaded MOT. John

[Robbie693]

I,ve had problems with this bleeding issue too(!) and my bleed nipple is bellow the inlet which appears to be the problem but, how on earth do you get a spanner on the nipple when it's above the inlet?

I had trouble as it is, only managing to turn the nipple half a flat at a time because the exhaust and chassis rail (spyder chassis) were in the way.
Is there more clearance on a Lotus chassis, do others remove the exhaust, special tools...?

[GrUmPyBoDgEr]

Robbie,
yes as you say it's a pig of a job. Mine also has a spyder chassis. I'm not sure what the clearance is like on the Lotus chassis but on mine about the only way to get access is to remove the exhaust.
John

[tdafforn]

Hi both,
Sad to say, its easy with a lotus chassis
tim

[Robbie693]

Great

Thanks both

[ElliottN]

I have recently overhauled my clutch slave cylinder and fitted a neat little system for bleeding - in this case supplied as a kit by the Elan Factory in Melbourne (Oz).

I have replaced the on-cylinder bleed nipple with a "remote" bleed nipple. This is a length of s/s braided fluid line which has a banjo union at one end (which is locked into the slave in place of the bleed nipple) and a bleed nipple at the other end (which I've mounted vertically on a bracket appropriately positioned on the firewall).

Makes Elan clutch bleeding a very civilised task.

[GrUmPyBoDgEr]

Elliot,
now that is a neat idea, no doubt it could all also be assembled so that the the bleed in the cylinder is also held in its uppermost condition.
When I rebuilt my Elan I fitted remote resevoirs for the brake & clutch master cylinders because I knew of the access problems.
I wish I'd known then that the 2.5" dia. exhaust system would get in the way of the slave cylinder so much.
Definately the next improvement to be made when I get in there to put a replacement gearbox in!
Thanks for the tip.
John