Bizzare brake problem
Turbo Mini Forums

Has anyone or does anyone know anyone who has ever had a problem like this?

To start things off my brothers mini was loosing brake fluid. Eventually we traced it to be running into the servo so i changed the master cylinder as the seals were obviously gone. After it was all back together and the servo had been given a good clean out the brakes were spot on and we had a good solid pedal (whilst driving forward) When you reverse quickly however the pedal goes straight to the floor and there is hardly any brakes at all and when you drive forward again its spot on again.

So i changed the servo in case the fluid had damaged the diaphram. The problem remained. Ive also changed the vacum hose and tried yet another master cylinder. Still no joy. Ive had the rear brakes to bits tonite to make sure everything was all together right and 1 of the shoes were on the wrong way round so changed that but guess what???? Still no brakes in reverse. The only thing i havent changed is the bias valve. There are no leaks anywhere now.

Anyone got any ideas cos im totally lost?????????????

Hi,
Wheel bearings?
Cheers,
Gavin :)

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I had a bizarre brake problem a while back, not the same as yours though. I eventually replaced every brake component in the system and the last thing I replaced was the MC which fixed my problem. I know this probably doesn't help but you have already started changing some of the components so I would go with changing the brake pressure regulator for a brake bias valve if you have the split front/rear that is. Are you losing any brake fluid from the reservoir?

Cheers for your replies. No there is no leaks from anywhere at the moment. I was gonna change the bias valve but ive just got a fealling it wont change anything. Im letting my brother use it at the moment and have jus told him 2 be carefull when brakeing in reverse. I think it might be 1 of them problems il neva find cos ive nearly changed everything now.

There has to be a logical reason for this and it seems that it cannot be hydraulic.Caravan brakes have a set up where the shoes fall away from the drum when you reverse, so that the over run brake system doesn,t prevent you from doing so. You said that you found some of the rear brake shoes in the wrong way round.Is there a possibility that you have something going on in the rear drums similar to the caravan setup?

Could be something mechanical, brake shoes bearings etc.

What may be happenning is that when you reverse, the shoes or pads are forced away from the drums a little and then you have to take up the slack. After reversing fast if you pump do they work again? if you reversed hard and did not brake then went forward does the pedal still go to the floor?

A similar thing used to happen on my TR in that when you cornered hard the flex of the disks forced the pads back a little and when you next pushed the pedal it went a little further down than normal, more than a little disconcerting!!

Edited by Turbo Tel on 15th Jun, 2008.

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Yeah if you pump the brakes after reversing fast they work spot on. I know what you mean about the caravan brake set up and i think the problem must be in the rear drums. When you go forward after reversing quick the pedal does go down further the first time you brake after reversing. I think il buy a set of new rear shoes cos ther prety worn anyway and see wat happens. Thanx for all your comments. The caravan brake logic does seam to make sense.

Check that BOTH pistons in the rear wheel cylinders are moving freely.
Often just one of the pistons sieze up in a cylinder so you do still have (reduced) rear brakes but the shoes don't centralise properly when adjusted up (as the adjustment relies on both pistons moving together) and this can have different affects backwards to forwards because of the leading shoe / trailing shoe design.

Schrödinger's cat - so which one am I ???

Very good point. Worth checking. 1 of the cylinders is new but it could be either at fault.

Found the fault. Came to change the front tyres and noticed mega play in front ds wheel bearing. There was about 10mm play in the wheel. Changed bearing and now fault has gone. Its so simple to think how it was causing the fault as well. 10 out of 10 for the man who said wheel bearings.