Brakes binding and sticking on.

[Mudchute]

Hi all,

I've read the multitude of brake binding problems but none quite fit the symptoms I've been experiencing with my B5.

For the past few mornings the brake pedal has been slightly spongey but after a few applications of the brakes it went away until the next morning. The pedal also travelled so I put this down to a failing master cylinder with an internal leak. No other problems occured at the same time as this.

Until yesterday that is.

Driving around normally I noticed the car was requiring more power to move. I stopped and found the o/s/f (drivers front) and n/s/r (passenger rear) brakes were smoking heavily and binding on. The other two brakes were fine. At the same time this occured the pedal was becoming harder and harder and the bite point was there already as asoon as you looked at it with no travel at all.

I've replaced the master cylinder and at the same time looked inside the servo (all clear and like new inside, scuttle drains claer too).

I'm waiting for some new rear calipers and rear discs and pads to turn up as the bleed nipples are small mounds of rust before I can complete the job but I'm concerned there's more problems waiting for me upon completion. I have replaced the front discs and pads recently (last 6 months) and cleaned/greased the calipers up at the same time. I didn't observed any faults with them at that time and I've no reason to believe they have any issues.

Does what I've described sound like a master cylinder issue? I recall reading somewhere that the brakes are split into two diagonal circuits and that if the master cylinder where to partially fail and keep the brakes on then its possible that only one circuit would be affected hence my symptoms. I need the car for work so I'm trying to pre-empt' any other issues leading to minimal down time.

Thanks guys!

[fourringsrus]

Not an expert on b5's but sounds to me that you are on the right track with the master or servo internals

[spartacus 68]

Not unusual to get seized brakes given age of car. Audi sell kits (rubber 'o' ring, new dust sleeve). I'd also check condition of piston bore. If light surface corrosion, it can be cleaned with wire wool and mineral oil such as 3 in 1. Lightly grease under dust sleeve with Lockheed red grease and lube sliders. Do full brake bleed afterwards.

To rule out further brake issues with binding calipers, drive car for 5-10 minutes and coast to stop. Brake discs should be cool to touch.

[vwcabriolet1971]

Could be that the brake hydraulic fluid needs changing. If a large amount of water has been absorbed it could give rise to vapour lock giving the conditions you describe.
If the symptoms disappear after the brakes have cooled down then this is the likely problem.