Brakes coming on automatically

[iahmed82]

I’ve had a m54b30 swap, after driving the car for around 20 minutes, the front brakes gradually apply, the car no longer rolls at the lights, this gets worse as the minutes pass.
If I turn the car off, wait a minute and start it again, the brakes “reset” and the process starts all over again.
I have the clip servo fitted.
Thought it could be the brake master cylinder, just changed that but no luck.
Then thought it could be callipers but a seized callipers wouldn’t reset if the car was turned off and on within a minute and then seize back up after 20minutes and also the callipers aren’t actually seized.

Mechanic who did the work to my car is as confused as I am, can’t work out what it is.
Could it be something to do with the vaccine apply pressure over time?

Please help!!

[iahmed82]

Ok.. so found that if I take the vacuume pipe out and put back in it frees up the brakes… puzzled on what to do

[Speedtouch]

Sounds like a build up of too much vacuum, that should probably be moderated or released with a valve, perhaps. Check the brake servo and master cylinder for any such valves and clean/replace them if required. There may well be such a valve fitted in the hose from the master cylinder to the inlet manifold. Also check the hose isn't collapsing in on itself, which can happen if the rubber has gone too soft.