Help with brakes !!

[Martin62]

So,

I've been having an issue with one of my rear brakes binding on my 20v Quattro.

On a couple of occasions the pedal almost went to the floor and needed pumping to stop the car, I assume due to overheated fluid. The wheel didn't feel too hot and the disc wasn't glowing so I was a little surprised.

Strangely, once cooled as was normal again, except for the binding.

I have rebuilt the offending caliper and all is ok now with one exception, the brake bomb seems to be shot !

Pedal is rock hard on first start up of the day and warming light comes on autocheck for 5 seconds or so until pressure is restored.

Can this be caused by air still being in the system ?

I have realised that I didn't bleed the master cylinder just the calipers, could this be the cause ?

I must admit this car is trying my patience at the moment !

Any suggestions ?

Cheers,

Martin

[UrS4boy]

Don't know your issue but 5 seconds of brake bomb light is not one of them.

You can't/don't need to bleed the master cylinder unless it was totally empty of fluid. Even then, the bleeding involves pushing all the air bubbles out to the calipers/wheel cylinders. People often use a different coloured brake fluid when doing a major bleed/fluid replacement so they know when the new fluid is coming through (otherwise the fresh stuff will be more clear/less brown than the old stuff).

Proper brake bleeding starts at the wheel furthest from the master cylinder and then moving progressively closer. Pressure bleeders are the best. Otherwise a one man bleeder attached to the bleed screw and manually depressing the brake pedal - but never further than the normal travel - otherwise you will push the piston seal past the wear ridge in the master cylinder bore, potentially nicking the piston seal, causing a leak which will mean you have to pump the pedal to get it firm during braking. Solution is a master cylinder rebuild or a new or rebuilt master cylinder. (A less I first learned when I was 16 - 48 years ago. )

BTW the clutch slave cylinder need to be bled in the brake bleeding process too.