20 replies to this topic

[Bristolmini]

I have just fitted nearly a whole new braking system to the car:

braided hoses
new rear wheel cylinders
new rear shoes
finned drums (not genuine minifins but similar kind of thing)
metro 4 pot calipers
new mintex pads
new discs

I am now having a problem which may be related to bleeding the brakes, the pedal has a lot of travel, about half way and is then a bit spongey (pumping the brakes when moving makes them better)

I cannot find any leaks

when bleeding the brakes I am not really getting any air out (possibly the odd bubble smaller than a pin head)

The brakes are actually better with the engine not running ie without a servo, there is much less pedal travel. This is the bit I don't really understand, the servo should make the brakes better not worse.

Any suggesttions of what may be wrong?

Had a look through previous posts but I am yet to come accross anything that I think would solve the problem.

Thanks

[TOMMO0302]

Not sure about the servo side of things as never had one, but a common problem with fitting metros first time is that you can get them upside down. You have 3 bleed nipples on each caliper, 2 centre-ish either side nd the other should be at the top as opposed to bottom. You got them the right way?

[Bristolmini]

Yep bleed nipple is on the top on each side

[cowboy]

what type of brake master cylinder do you have?

if you have the twin cylinder master cylinder, you might need to bleed the top half of the master cylinder at the cylinder, crack off the top union and bleed it, you will find that you can then bleed the brakes.

this is a problem i had when i did my brakes after overhauling them.

cowboy

[Bristolmini]

I beleive it's the later type tandem system (attached to the servo)

So doesn't have a 'top' union

[TOMMO0302]

What are you using to bleed them with?

Also, not really related but what 'mini to metro' conversion kit did you get? I got some from ebay (cant remember the brand now) and they were a pain to fit, when i say fit i mean get them to actually seal at the unions....only noticed them leaking as had an eazibleed on them and could see the fluid dripping onto the floor, maybe fluid wouldnt come out but yet air get in if your not using such a high pressure system of bleeding?

IF its servo related, try a quick search, i remember a thread on problems with the servo but not the details sorry

Oh, and you have got a haynes bleeding them in the right order according to your system...?

Edited by TOMMO0302, 09 January 2007 - 11:38 PM.

[Bristolmini]

I am using the gunsons eazybleed which you connect to the tyre to force the fluid through.

The front hoses I am using are the goodridge braided 4 pot conversion hoses, which as far as I can tell are the best ones to get.

Will have a look for servo related stuff now, although the servo was working fine before I took everything apart.

And I am bleeding them in the order given in the haynes manual.

Edited by Bristolmini, 09 January 2007 - 11:41 PM.

[TOMMO0302]

Fair enough, i agree about the goodridge hoses, they came off mine as they were kinked and replaced with these others which were simply....a nightmare!

Probably not servo then.

You could try leaving the master cylinder cap loose and brake pedal depressed overnight? Thats me all out of ideas sorry

[Bristolmini]

Might try keeping the pedal pressed overnight, although the weather and time leaves me to think that tommorrow would be better for that.

[TOMMO0302]

Well i think its safe to conclude its not down to the fitment or actual parts used, so the best advice i can give is to tap 'bleeding brakes' into the search box...there are numerous ideas for solutions and probably the one your after! Let us know how you get on!

[Bristolmini]

Well I thin k the plan will be tomorrow to:

Check for any leaks
Bleed the brakes again
Leave the brake pedal pressed overnight (well it can't do any harm)

It's just odd that the brakes are better without the engine running than when it is

[TOMMO0302]

Have you got it somewhere where you will notice the leaks i.e. a garage? If not, that could be your issue. As you say though wierd it makes a difference with the ngine on which would point to your servo, but then you said that was fine before! Im sure someone will be along soon with more ideas!

[fikus01]

lots of pedal travel suggests air trapped in the rear loop or the pressure valve or the fisrt part(nearest pedal) of the master cyl.

[Bristolmini]

Air in the master cylinder is a possibility, I already had all the bits to change the brakes and I was forced to do it early because the seals in one of the rear cylinders went and emptied out a fair amount of brake fluid (enough to empty the fluid reservoir)

This was unexpected because only a week or so before the fluid level was fine and the warning light didn't come on, amazingly the bulb test works and the wires were connected to the cap. It goes to show that just because there are wqarning lights it doesn't mean they actually work.

If I have got air in the master cylinder what is the best way of getting it out? apart from contantly bleeding the brakes?

[TOMMO0302]

Probably not the 'best' way, but i took off the brake line from the master cylinder, put my thumb over the master cylinder output bit (where i just took the line off) and started pumping the pedal...ackward doing it one man but soon you'll feel the pressure building up....of course, a full bleed is required after that again