Handbrake works foot brake does not

[orsum]

Today I took my S2 ABY coupe to my local Audi workshop today to test the shocks (they all passed) while on the machine they tested the brakes.

The fronts passed with flying colours.

The rears passed with flying colours when using the handbrake but failed completely on the foot brake. When I say failed they did not do anything the wheels kept turning.

The Audi guy said bleed them and he will do the test again.

Yep I will bleed them but has anybody ever heard of this type of failure before.

5 years ago the brake fluid was replaced and it has done 1000km since then. No other work has ever been done to the brakes.

I am assuming at this stage the calipers are fine as the handbrake worked correctly.

Anybody have an idea what could be going wrong?

[John.]

When bleeding the brakes, if you get a sufficient amount of fluid through the rear bleed nipples then this would suggest all is good except for the calipers.

[Monkeymagic]

Id start by stripping the rear pads and making sure they are free. While the caliper is free get someone to gently press the brake pedal, see if the piston moved freely. Don't press hard as you will eject the piston.

[piotr]

As above-I would bleed them first and see if the piston is moving.if not I would suspect master cylinder

[orsum]

After a bit of searching and reading it does sound like the master cylinder.

Seems like quite a few people have had the same issue.

Will bleed them first. Car coming back from more cosmetic work in two weeks.

[orsum]

Yesterday I bled the rear brakes and I am shocked at how much air came out on both sides.

I still have some very very fine bubbles coming through but the brakes are working much better.

Never did the fronts.

I used about 1 litre of fluid, the fluid was changed 5 years ago and had less that 1000km of use. How the hell did all the air get in the system, there are no leaks.


Bottom line is the brakes needed bleeding and now the discs are cleaning the pitted surface of the disc which indicated the calipers are working.

Will test them and report back how effective the rears are operating.