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BLEEDING THE BRAKES !! ??

Posted: Wed Nov 05, 2003 9:29 pm
by Arfron
I have renewed the brake lines ; put two new rear brake cylinders ; a new master cylinder ; and using silicone brake fluid . However , even using an Easybleed unit , I still cannot get the air out of the system ! When I press the pedal it requires one or two pumps to get the full hydraulic pressure . I have a small leak from a union connecting the rear wheel cylinder . I need to change the copper washer , I don't think that the leak is the main cause of my problem ? Also , is it normal to have a small spurt of hydraulic fluid squirting upwards from th m/cylinder reservoir , when you press the brake pedal ? ( when I say small , I mean about half a cm. at the most , or breaking the surface , nothing too dramatic ! ) Any suggestions on the correct bleeding process / tips would be greatly appreciated . Thanks :roll: Arfron
( Ps . Ihave just noticed the notes made on Page 2 by Cam / Chris ; however, how do you get the air out of the 'new' Lookheed M/cylinders etc ??)

Posted: Wed Nov 05, 2003 11:55 pm
by rayofleamington
the master bleeds itself quite well. the small spurt is normal.

to bleed a complete system including wheel cylinders...
I would partly dissassemble the rear brakes, and press the pedal to push the pistons out - then push them back manually. This helps push the air out of the cylinders. (more important on the front ones though..)
but dont push the pistons out too far.

Posted: Thu Nov 06, 2003 1:36 am
by Kevin
Any leak will tend to give a soft pedal as its letting air in, and when bleeding you start with the one furthest from the master cylinder and the final one of the 4 should be the nearest (you did bleed all 4 I suppose).
I have also heard that silicon fluid can sometimes be a so & so to bleed properly and I think that you need to have pressure on the pedal even before you open the 1st bleed nipple if there is a problem it becomes a two man job, I wonder if anyone else has heard or experenced this problem with silicon fluid.

Posted: Thu Nov 06, 2003 1:04 pm
by rayofleamington
generally silicon can be a disaster unless you replace all the seals.
Old seals that have sat in brake fluid for donkeys years do not always work with silicon fluid...

Even if you replace all the seals, silicon fluid is still more difficult.

Thanks for the advice

Posted: Thu Nov 06, 2003 8:11 pm
by Arfron
Thanks for the advice on bleeding the brakes ; clearly silicone brake fluid was a mistake in the first place . In fact, I have not used it before , but on readingh the advice given in various restoration manuals , I thought I'd give it a go. The only seals I haven't replaced are the front cylinders , so I assume that I should change these seals as well. If all this doesn't work can I revert to ordinary Dot brake fluid , without too many problems ? I must say that I have worked on variuos makes/ Lockheed / Girling and have not experienced so many inherent problems . Ah wel-- back to the drawing board !!
Thanks for your help very much appreciated :roll: Arfron