Weird Brake Problem

[DPJ]

In my time :cough: I've encountered and sorted most brake problems but this one is really puzzling me.

After driving my 8v Mk2 for longer than 20 mins or so, I start to get quite a bit of pedal travel. Normal driving - the brakes work fine, but disconcertingly the resistance is a fair bit down towards the floor. Pumping makes no difference.

After parking up and leaving it for a while, it returns to normal. The servo seems to be fine, it does what it should do when you test it.

I've had a sticking caliper slider on it before, I don't think it's that. Front discs and pads are virtually new. Rears are good. The brake fluid is probably past its sell-by date, but we're not talking about a problem under heavy braking here. Not losing any fluid.

I need to check the one-way valve in the servo vac line.

My other guess would be master cylinder seals, but I don't see how it can be poor one moment and fine again a bit later....

All thoughts welcomed.

 

[edc]

Maybe worth checking the feed on the manifold for the servo.

 

[warren_cox]

Can't add much to this, but I had a similar issue on my Mk1 Golf GTi and my mate replaced it with a new Mk2 Golf 16V master cylinder and all was well.

 

[DPJ]

Sorry, I'd forgotten this thread. Problem was a sticking rear caliper boiling the brake fluid.

 

[skeeno]

i was gonna say sticking caliper happend to me just before mot it was solid it was the bottom slider on the caliper carrier with the rubber boot on it was wedged solid inside its housing
bit of grease works a treat now