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Brake bleeding - zero pedal pressure.
emwmarine - 4/6/12 at 05:02 PM

Help appreciated here greatly.

I have fitted two new Girling Master cylinders (0.75 and 0.625 bores) into my part built kit. New pipework leading to new hi-spec calipers.

The complication is that the calipers, though new, date back to 2003 when the kit was originally purchased.

I assumed they would be ok and have filled the system with fluid and tried to bleed it with a vacuum bleeder driven off my compressor. However when I went back to try the pedal having thought I had bleed the system there is no resistance at all from the master cylinders to the pedal. In fact I ca push them in and pull them out, via the bias bar, at will.

So is it that the seals all rotted, despite being new and unused to the extent where they do nothing, or have I somehow still got loads of air in the system. The master cylinders are mounted horizontally so I can't see where a huge amount of air could hid.

A bit flumoxxed and annoyed I might have to take the pedal box apart again.

jacko - 4/6/12 at 05:20 PM

I would say keep bleading but try it the old way 2 people and see how it goes
jacko

steve m - 4/6/12 at 05:42 PM

Agreed, try the reall way of bleeding the brakes, with a m8!

pmc_3 - 4/6/12 at 06:08 PM

I ask this every time as it caught me out the first time lol calipers on the correct sides? bleed nipples need to be at the top otherwise you wont get the air out

rusty nuts - 4/6/12 at 06:22 PM

quote:
Originally posted by pmc_3
I ask this every time as it caught me out the first time lol calipers on the correct sides? bleed nipples need to be at the top otherwise you wont get the air out


Could be wrong but I think Hi spec calipers have 2 bleed nipples , one at the top and one at the bottom . Some cars with Sierra rear calipers can have them fitted upside down (bleed nipples at the bottom).
I've never had a lot of success with vacuum bleeders whereas a pressure bleeder seems to work well even if you need to pump the pedal a few times to get things working.
Check that the rear brakes are correctly adjusted and also the master cylinder push rods are not over adjusted

britishtrident - 4/6/12 at 06:30 PM

You can test the master cylinder by screwing in nipples in place of the outlet pipes and giving a quick bleed -- 2 pumps is usually enough.


No matter what method to use to bleed the brakes the master cylinder must be pumped full stroke two or three times, don't open the nipples to far just enough to give a decent flow.

I would suggest you bleed the brakes using either the normal method or an Eezibleed pressure bleeder, pump the pedal slowly especially on the return stroke once the fluid runs clear close the nipple. Then bleed the opposite brake in the circuit, bleed the other circuit.

emwmarine - 4/6/12 at 06:50 PM

I did have one go at 'normal' bleeding, will try again.

Chippy - 4/6/12 at 10:09 PM

Do you have Sierra disc brakes on the back, and if so are they mounted with the bleed nipple at the bottom. If that is the case you will need to remove them and turn them so the nipple is pointing upwards, and wedge something between the pads so you dont push the pistons right out. HTH Ray