14 replies to this topic

[Dog]

HELP!!

I'm having trouble getting a decent pedal in my Van...
I am running a single line system...

I've replaced the Master Cylinder, all the rear brakes (which I have found hat I now have a leaky cylinder, even though it was new :mad:) I have Cooper S 7.5" Calipers on the front, I've bleed, them and bleed them, and can't get any more air out from pumping the pedal.

When it goes "harder" it still nearly hit the floor, and its now where near as hard as it used to be (even that was poor) but its goes perfect after pumping the pedal about 5-6 times.... Once its hard if you keep the pressure on, the pedal stays hard.

So going to replace my cylinder, what else can it be that can cause such a weak pedal?

Also, I've noticed that with one side built up, its "stiff" to turn, and adjustment is minimal before it stops (perfect adjustment) but the otherside, spins round nicely, but I have no adjustment at all... like I said I've bought brand new built up back plates... I've racked my brains and I really CBA now...



HELP!!

[Pie]

We had a job like this in at work abuot 2 weeks ago. Ok it was on an 55plate A3 sportback, but it might be the same problem.

We had to replce the master cylinder, and all the seals with it. then power bleed the brakes abuot 4 times then bleed them propperly

[Dog]

Well it would seem pumping does f**k all lol and does seem as if it need injecting/forcing the fluid though to get the air out...

But now I've got the rear cylinder gone, I can't adjust it up, so will have to wait for a new cylinder...

But something that I've just thought off... before I found all this out, I found I couldn't get the drivers side to adjust tight (in fact it never adjusted full stop.) what could this be?

[Pie]

broken

[jack_marshall]

New systems are a bugger to bleed up sometimes. Get an easy-bleed kit on it!

[Dog]

Yeh looks like thats the only way... unless I replace the cylinder, work out why my one drum won't adjust, and take it to the garage - let them have a headache lol

[DannyTip]

When my system was completely empty i had the car up on stands, filled the master cylinder up full left the cap off then opened all the bleed nipples. A few minutes later it started started to come through the nipples so i then closed them off and bled the brakes the normal way Perfect pedal.

[mini13]

sounds like the adjuster on the drivers side is buggered, if you can't get the adustment upp the pedal will be on the floor and feel rubbish. you need to pull it off and check it out.

once thats sorted i find a long length of fish tank hose from the bleed nipple back to the master cylinder works well, you can then pump it nice and quick to force all the air out of the high spots.

[Dan]

Have you fitted the Cooper S single line master or a drum braked one?

[Jupitus]

When my system was completely empty i had the car up on stands, filled the master cylinder up full left the cap off then opened all the bleed nipples. A few minutes later it started started to come through the nipples so i then closed them off and bled the brakes the normal way Perfect pedal.

Hmmm wouldn't that put air-infused fluid into the master cylinder though????

[Dog]

erm, well I refitted the original master, its better, but not perfect - will never be reason for chainging.

As for changing the master to a Cooper S one, no idea,I got a plastic bowl type - non-orginal - off Minispares...

[Jammy]

Blank off your rear brakes at the rear subframe. Bleed the fronts and see what the pedal is like then. If you get a good pedal you know its the rears. If you don't you know it could either be the fronts or the master.

[Dog]

Well tis all things I can try... but stuffed it and placed the old master back on, and the pedal that I had before is back, so I think I might have a dodgy new master, OR Minispares has surpplied me a Clutch master rather than a Brake master (even though the box was marked Brake master)

A phone call will be made on Monday, see if I can get a replacement (and darn Simon's on holis )

[Dan]

Calipers use more fluid than cylinders. The Cooper S had a different single line master from the other cars because of this, which pumps more fluid (it's a larger bore which is why you then have to fit different size rears to maintain the balance). Sounds to me like that's the problem since you say it almost starts to work at full travel. Master Cylinders are expensive though so I'd check these ramblings with someone else and exhaust other options before running out to buy one, I'm not entirely sure you see. I do know that you shouldn't go messing with the hydraulic design of the brakes without understanding what's going on though.

If you want to check whether you have a brake or clutch M/C, the only external difference between the two is the shape of the baseplate.

[blacktulip]

watch when bleeding brakes, if u pump the pedal too fast and all the way to the floor it can pop the seals in the master cylinder. i was told only to press half way when bleeding. i had the missus pumping hers the other day and she blew the seals which is a right sod as u dont know its them and curse the brakes lol