12 replies to this topic

[garzz75]

i have an issue with my mini 1984 mayfair braking system all four wheels are binding, i can travel only about 8 miles before pedal goes rock solid then ive to limp home in 2nd.Ive replaced front flexes and compenstor valve if i leave it the presure releases its like if i press the brake two or three times on the journey home it just keeps on building pressure do you think the master cylinder is faulty.any comments please prefer helpfull ones though lol.

[OhDear]

Oh scary. my only concern is tho why are you using brakes

[garzz75]

lol i try not to but most modern cars arent made with indicator anymore grrrr.

[minimissionary]

any comments please prefer helpfull ones though lol.

This IS an internet forum you know...?

[Rich1275]

could be a master cylinder faulty. definatly all four wheels binding?

[garzz75]

yes all four were, i stripped the brakes lastnight it has a broken rear adjuster.I replaced it then adjusted all shoes seems to be ok this morning fingers crossed.

[tiger99]

If that happens, it is ALWAYS because the master cylinder pushrod is effectively too long, pedal not returning fully, or master cylinder piston sticking internally (that last one will imply a wear ridge in the bore so the cylinder is scrap). It is NEVER caused by one failed brake adjuster.

The piston (both in a dual circuit system) must return fully to open the reservoir port(s), otherwise hydraulic pressure becomes trapped in the system. It also prevents bleeding the system in the normal way, although a pressure bleeder may sometimes apply sufficient pressure to overcome the problem temporarily.

There seem to have been a few people chasing round in circles recently with their clutch systems, when the problems they were describing pointed to exactly the same problem.

[garzz75]

would changing brake pedal assembly cause this problem as my mini was an auto, the pedals i bought came from a early mini no idea of year

[tiger99]

Yes! Exactly that, if any changes made the master cylinder push rod effectively too long, by changing position of cylinder mount with respect to pedal, or changing pedal return stop. There are lots of differences between early and late pedal boxes. I assume the fairly heavy pedal return spring is fitted and working on both pedals?

You can do a simple test. Jack up a wheel so you can feel for locked brakes. Undo the two master cylinder fixing nuts and lift it up as far as the hydraulic pipe allows. If the pressure is now released, the cause is proved.

Your best bet is to carefully consult the Somerford web site to see which bits you have, or should have. It may be that something, such as the wrong brake light switch, is preventing the pedal returning fully. There is not much access to the top of the pedals and the master cylinder push rods, as you will know, having fitted a pedal box, so it may be difficult to pin this down, but it may be that you need one or more spacer plates to lift the master cylinder slightly. NAM1718 on the Somerford web site are used in pairs, quantity "as required", which to my mind says that adjustment is often needed. I assume you have the gasket fitted, as its thickness may make all the difference, and you need it to keep fumes from entering the car. There perhaps should be a gasket under the plate which carries the cylinders and top engine steady too.

There should be a trace of free play between the push rod and master cylinder piston when the pedal is fully up, and all dimensions are correct, but I don't know how you would be able to feel it in there.

I should have asked if you have a direct acting servo, because that is between pedal and master cylinder, and could cause the problem. Also, the pedals and the pedal box are very different.

http://www.somerford...page=page&id=57

[garzz75]

thank you tiger 99 for the helpfull advice i will see if that test works thanks again

[79ballboy81]

I've got exactly the same issue with my mini. Did the fitting the spacers fix the problem?

[ChopperHarris]

I had a friend with this problem about 30 yrs ago!
Due to refitting master cylinder without the gaskets above and below the engine steady plate.

Why is this thread entitled "DRUM" brakes?
84 Mayfair has discs?

[G4RZZ]

A Reg Mayfair auto twin leading front brakes yellow tag master cylinder