Someone on here said this once. If you can't run water down a brake hose, while its off the car, then you need to replace it.

Thanks everyone for the input lots of info flowing!

ogyris-yeah mate if i can't figure it out i'm just going to take it to a brake place.....try and save my $$$ first!

Benny-i'm going to give that a go, could you get away with using washers?

Thanks

My money is on the [new] master cylinder piston is not releasing back all the way and partly blocking the hole to the reservoir [the pressure will build and build]. Being a fixed length rod between the brake pedal and the MC, this can be an issue when replacing the master cyclinder. [This is all based on the assumption your car doesn't have vacuum assisted brakes]. There are shims availble that sit between the firewall and the MC to obtain the correct position.

cheers
benny

I had a similar problem on my 1200. Basically the pedal became hard and my front right brake was grabbing and almost locking up.
I knew it couldn't be the callipers because they had been rebuilt, so I took the brake line off and cut it open. To my horror I found the rubber inside had degraded and almost blocked the line. Once replaced with a better line from the wreckers, brake bleed, no more problems!
If in doubt, chuck them out. Take the car to a brake place if still stumped.

I checked the lines the closest point to exhaust is prob 50mm

Fluid was brand new Castrol suitable for dot 3 and 4...is that stuff alright?

Yeah its disks up front and drums in rear, only back left sticking though, thats the reason why i thought it could be the cylinder, but again it builds up over time so :S

Nige gave me a hard pedal a couple of times as did don recently.

Unlikely it's boiling. More like a sticking wheel cyl.

Are you running disks up front and drums rear? If it was drum all round did you remove the residual pressure bung? If not that causes the brakes not to release from memory

how old is the fluid? if it has water in it it can reduce the boiling point as fluid does absorb moisture from the air over time.

The exhaust would have to be right on it to produce enough heat to boil the fluid. Wouldn't it??

I thought it could be that also so i adjusted the shoes right off and also the handbrake. Didnt think of exhaust how close is too close? Can you wrap the lines in anything?

Thanks

if it happens after driving around maybe its a problem of the fluid boiling up is your brakes to tight so when you drive it creates heat? or maybe exhaust is to close to the brake line making the fluid boil and expand?