Binding brakes, ABS Fault?

[duffA6]

I have a 2001 1.8t Audi A6 which I am getting a bit sick of!

Apart from the dashboard lights for the speedo etc which have stopped working, and the boot catch which dosen't catch, my biggest problem is with the braking system.

Last year I started to notice that fuel economy was dropping, at the same time I noticed that my brakes were getting warm. This got progressively worse to such a point that the discs turned blue and the car slowed quickly to a standstill when I took my foot off the gas.

I took the car to a local Audi / VW specialist who stripped the callipers and changed the discs and pads. This improved things for a while, but soon after it started again.

When the engine is cold the brakes are ok, but as soon as the engine is up to temperature It felt like the brake system was already pressurised when I pushed the pedal down.

Again I took my car to the garage who then replaced the master cylinder. This seemed to work for three or four months, although I was told that there may be a problem with the ABS unit if the problem recurrs. Sure enough it's started again.

I have disconnected the ABS Unit electically thinking that there may be a problem with the ABS pumping up the system, but the symptoms still persist. Please help if you have had similar experiences or an idea of what the problem could be?

Thanks duffA6

[Peter D]

Is the fault common to both brake circuits. I would also be tempted to run the car until the fault is present and leave it running, whip off a wheel or slide under and undo a bleed nipple to see if the system is actually pressurised. Is this an automatic and do you have an electrical vacuum pump by the ABS unit. Regards Peter

[duffA6]

Hi Peter

Thanks for the ideas.
The brakes seem to be binding all round mainly both front brakes. The car doesn't pull to the left or right, and both front discs get hot. The car has a manual gearbox, and I can't see anything that looks like a vacuum pump next to the ABS unit. When I get a chance I will try to find out if the system is pressurising as you suggested.

DuffA6

[duffA6]

Looks like the problem has been found. I took the car into a different garage and the mechanic took it for a test drive, and said it feels like a servo problem. He stripped out the servo and found that the piston was badly corroded and sticking. I am now waiting on delivery of a new servo. Fortunately it is covered by warranty, phew!