Strange rear brake behaviour
Turbo Mini Forums

Hi all

Rear brakes have been adjusted as per Haynes manual. I have normal vented 4 pots on the front and standard drums on the rear. I have just been out for a drive (about 10 miles) and the rear brakes are absolutely fine for a couple of miles and then they gradually bind on to the point where I cannot drive. So, I re-adjusted rear brakes so they were completely off to get me home. Once at home I again readjusted the rear brakes again as per normal and then went out for another run and exactly the same thing happened again??? When the rear brakes start to bind the brake pedal gets really hard right at the top and there is no initial travel in the pedal before the brakes engage.

Anyone experienced this before or have any ideas??

Cheers
Rich

Springs inside the drums given up being springs?

break cylinders fooked? staying open and not closing? damage to the drum or shoes?

Drives
-Ford S-max Mk2 Ecoboost
-Rover 100 VVC #2 - track project

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Yeah could be springs, brake cylinders are new.

doesnt matter if they are new or not some are still fooked brand new, fitted some to a car the other day and they were leaking from the seals and not pushing out, if they did they just stuck open that was genuine parts as well...

Drives
-Ford S-max Mk2 Ecoboost
-Rover 100 VVC #2 - track project

Searching is all you need on TurboMinis

i know exactly what you mean, i did the same the other week, replaced both rear cylinders, bled them up and stamped on the brake pedal and one of them more or less exploded.......will check them again!

how old are the rear hoses? could have broken down inside and turned into one way valves almost. i've had this with front hoses in the past.

also check the flexi hoses as these can collapse on the inside leting pressure in and not out, had this happen a few time before i went to braided.

other wise check springs

always looking for them bigger bunches of bannanas

Ok, starting to pull my hair out now. I have replaced both rear wheel cylinders, fitted new shoes and spring kit and bled system again but still having the same problem. I have removed drums and checked that wheel cylinders are working and not leaking and that they also return ok. The rear brake hoses are braided, can these still collapse? Thinking it's probably not these as what's the likelyhood that both of them collapse at the same time. So the only 2 things left that it could be is the master cylinder or the pressure reducing valve. Does anybody know any way of testing these 2?

Front brakes are working normally and not affected.

The thing I don't understand is that it only does it after about 3 or 4 miles and the brake pedal goes right to the top aswell and there is no initial travel before the brakes engaage. I cannot replicate it whilst stationary in the garage just pumping the pedal. The only factor I can think of after driving 3 or 4 miles is that there is a build up of heat under the bonnet, can the heat cause expansion in the pipes (i assume only if there was air in the line) and lock up the rear brakes??

Can anybody think of anything else I have forgotten to check?

Cheers
Rich

What pressure reducing valve are you using Rich and what is the break set-up? Dual system with the valve on the bulkhead or single line with the valve at the rear?

It's the split front/rear system with the valve on the bulk head. I have given it a few wollops with the mallet too cos a read somewhere that the piston inside can get stuck.

I have standard vented 4 pots on the front with standard drums & shoes on the rear.

IMO those valves are the worst thing ever designed in the history of creation. I was chasing a fault for weeks before i ripped that off. Saying that it could be the master cylinder. I had a similar problem with my fronts many years ago which turned out to be the master cylinder.
Try making up a few short brake pipes and bridge across the regulator to take it out the circuit. That should atleast let you know where the fault is. Dont leave it without a pressure reducing valve though.

have the shoes got excessively hot at any time? if they have the glue/resin type stuff can work its way through the friction surface and onto the face of the shoe. then after a few miles this obviously becomes sticky again and your brakes lock on. then when you adjust them right off they can cool down and are ok when you adjust them back on.

just food for thought as changing shoes is a shed load easier and cheaper than a master or pressure ruduction valve.

sorry just thought of somthing, your wheel bearings are probably foooked, went for a drive in mine a few mins ago and i thought the breaks were binding its not the wheel bearings are shot. have you checked yours?

Drives
-Ford S-max Mk2 Ecoboost
-Rover 100 VVC #2 - track project

Searching is all you need on TurboMinis