11 replies to this topic

[Magnetagz]

I am having some troubles with my braking system at the moment and are after some advice.
It is a 1980 Mini van that I'm restoring, the original set up was a 2 circuit master cylinder but it had failed after being sat dry for a year, so I went to Minits to get a new one. They said that the original is not available any more so I would need the newer equivalent.
It looks the same and is still a two circuit but I have noticed that there is no switch in the side of it.
Excuse the vague descriptions but my knowledge is very limited on the maze on Mini Brakes.

Anyway my problem is that now the new one is fitted and the system is bled through, the pedal is quite soft up until half way then jams completely. I have tried re-bleeding the brakes and adjusting the brake pads with the nuts on the back of the hubs and no success.
Can anyone please shine some light on this issue, my thoughts were maybe it is to do with the pressure reduction valve maybe? or is the new master cylinder not compatible? I'm stumped.

Any help would be much appreciated.

Cheers.

[Dan]

Did you also buy the brake line alteration kit? Depending on exactly what master cylinder you had originally (there were 5 used between 1980 and 1985 I think) the front and rear lines may be the wrong way around. When the service replacement cylinders were introduced by Austin Rover / Unipart there were brake line replacement sets included in the service bulletin that corrected the issue. Only the section from the regulator to the master needed to be changed. There were also instructions for re-wiring the PDWA warning light system to a low fluid level system so you don't need the switch on the cylinder.

[Gulfclubby]

Did you bench bleed the master cylinder when new?

[KernowCooper]

Sounds as though the first circuit has air in it, and thats correct the older type is no longer available.

I would try and bleed it with a vacumm bleeder if you have one and try clamping off the front flexys to see if that improved the pedal, pointing towards air still in the system.

[Gulfclubby]

instead of typing my fingers off, this is what I mean.

[Magnetagz]

Cheers for the responses guys.
I did replace the pipes yes, the new master cylinder has metric connectors so I made new pipes, however I put them to the same holes in the pressure reduction valve as before, is this correct?
No I did not bench bleed, I had no idea about bench bleeding :S. Going to be difficult now in the car I'm guessing

[Gulfclubby]

not really any more difficult than on the bench. just have to disconnect the two brake lines and replace them with temporary bench bleeding ones going back into the reservoir. Of course you don't get the benefit of being able to change the orientation of the master cylinder to facilitate the air to escape. Only other problem is a potential for spillage, which in the car is going to lead to paint damage unless you clean it off well, which can be tricky at times because if restricted access to the bulkhead.

[Magnetagz]

not really any more difficult than on the bench. just have to disconnect the two brake lines and replace them with temporary bench bleeding ones going back into the reservoir. Of course you don't get the benefit of being able to change the orientation of the master cylinder to facilitate the air to escape. Only other problem is a potential for spillage, which in the car is going to lead to paint damage unless you clean it off well, which can be tricky at times because if restricted access to the bulkhead.

Good points, but it sounds like a must really. Luckily I bought a box of rags for the restoration so can fill the engine bay with them to catch any spillages.
So can I tick off the list the potential for incorrect parts fitted? Just trapped air?

[Gulfclubby]

Not necessarily. But bench bleeding is not going to cost you anything but a few pennies of tubing and a gulp of brake fluid. Might as well start with the cheap attempts of solving the problem before spending more money.

[Magnetagz]

Cheers for the help.

I hate Mini brakes...

[Dan]

I just had a thought, and it's probably wrong, but are you sure your car has front to rear split brakes? There were diagonal split systems being fitted until 1980.

Edited by Dan, 15 April 2013 - 07:51 PM.

[KernowCooper]

Here is the original AP Lockheed Conversion Sheet on converting the earlier master cylinders to the later Yellow Tag Master Cylinder.

And yes the pipes to the pressure valve were reversed.