brake bleeding - urgent help please

[olij]

Whats the dark art to bleeding brakes on a live axle then? I can't get the air out! going around the brakes as outlined in the assembly guide and still can't do it and am getting fed up of pouring brake fluid into the reservoir and getting air/fluid out.

 

do both the front and back left have to be bled simultaneously, whats the best technique? The master cylinder weaps into the pedal box - is this common or have I just mentioned the potential source of the problem?

 

any thoughts very gratefully received, needs doing before the imminent MOT....

 

thanks, Oli

[Paul Ranson]

If air was remaining in the system and causing a spongy pedal then you wouldn't be seeing it come out... So the air must be being introduced, either up the bleed nipple, in which case it's a consequence of technique, or elsewhere, in which case it's a fault.

 

The master cylinder leaking seems to be a 'fault' which must be fixed before further diagnosis is possible.

 

Front and back circuits should be independent. It's conventional to do the wheel furthest away from the master cylinder (in a piping sense) first. It shouldn't take very long.

 

FWIW if you're reusing fluid that could be a source of air, but see to the master cylinder first. If the system is in good nick then there's no need to reuse fluid. 500ml was enough to fill and bleed my old Superlight from master cylinder empty.

 

Paul

 

Edited by - Paul Ranson on 18 May 2001 01:23:58

[olij]

Master cylinder is the next target then. I have been using one of those one man bleeding kits and thought my technique was ok but you never know. No other leaks can be seen in the system. Thanks for the advice, I shall perservere. after a new master cylinder.

 

Oli

[John Whyman]

Technique I use from Mini racing days and being without assitance, is to get a length of 2 x 1 timber and cut it to fit the length between a FULLY DEPRESSED pedal and the cross member in front of the seat.

 

Undo bleed nipple and attach tube to catch spill in jam jar. Then depress the pedal very slowly with timber till at full extent and them jam the timber in front of cross member. Tighten nipple and release pedal very slowly so as not to suck in air.

 

Make sure that cylinder is topped up every time with FRESH fluid. NEVER ever use old fluid it will have air and possible water in it. Repeat process a couple of times for each corner, starting with nearside rear/offside rear/nearside front and offside front.

 

Check for leaks and pump the brake pedal a few times to get pressure before moving car.

 

Suggest you change master cylinder ASAP, remember your brakes are your life.

 

Happy motoring thumbsup.gif C7 WJW

[Fast Westie]

Oli

If your master cylinder is leaking then you should replace the seals before proceeding. Otherwise get one of those presure bleeder, they make things much easier.

[Paul Ranson]

I've never got on with pressure bleeders. Even at low pressures I end up with leaks, excessive fluid consumption and doubt.

 

The tubes with blobs on the end from most motoring stores for a couple of quid work fine. They even come in two packs for the fancy brakes on the front.

 

Paul

 

[olij]

Has anybody replaced the seals on their master cylinder before? if so where did you get the seal kit from as it is proving to be very illusive. Who manufactures the master cylinder - is it bespoke to Caterham in any way or could it be picked up cheaper from elsewhere?

 

thanks

oli