Master cylinder question.

bananacustard · Apr 20, 2008

Can anyone tell me if a later master cylinder will fit ( and work!) on my 68 or if I need to fit the correct one for a 68. The brakes need pumping at the moment despite being thoroughly bled with new fluid. There is no fluid loss and the present master cylinder is only about two years old. I can't work it out so assume it's a faulty master cylinder and if replacing, the new ones are considerably cheaper.

faux · Apr 20, 2008

Hi

I have a later MC on my 69 an it works great. Â£30 from GSF - it has to fit the reservoir, and if you are running drums all round I think you need the pressure valves from the old MC.

It does sound odd that there is no fluid loss, have you checked the brake hoses for bulges etc?

angus · Apr 20, 2008

Interesting that other master cylinders fit - can you point out which one in GSF? Thanks - was about to replace my old one for Â£120 but be nice to save!! 1968 Bay - sorry to hijack a tad....BTT

67 BAY · Apr 21, 2008

It could be your brakes want adjusting,badly adjusted front brakes can give this problem.

Steve

bananacustard · Apr 21, 2008

Brakes are all adjusted well and brake hoses are in good order with no bulging :? Glad to hear a later one fits. I'd like to get the old one working though, I checked my old paperwork and it's less than two years old. Could it be a bit of crud in the cylinder blocking one of the holes and affecting the flow of fluid back and forth?

Clarkson46 · Apr 21, 2008

Does the pedal feel spongy as though the brakes need bleeding? What usually happens is either the cylinder has some pitting which allows fluid to bypass the seal or the seal is worn and allowing fluid past it. Either way the only way you are going to find out is to strip the master cylinder and look. As far as I'm aware the pressure valves were discontinued years ago. Our '68, running drums all round, had none and is fitted with a later master cylinder which worked fine until we upgraded to later brakes all round.

bananacustard · Apr 21, 2008

The pedal's not spongy. It just travels a long way until the brakes work but they do work very well for drums. If I pump the pedal once or twice the brakes work well but with the pedal a lot higher. This stays like this as long as I don't take the pressure off e.g. going down a hill but if I release the pressure they are immediately back to how they were.