Brakes not working - pedal like a rock

[B4 Cab Simon]

So the red (!) started flashing while driving but everything seemed fine. I had a look the following morning and the PAS Fluid was high and the brake pedal was like a rock. With the engine running and foot on the pedal it pulsed. I fitted a 2nd hand Accumulator and flushed the fluid cleaning the reservoir & filters then refilled with Audi Green fluid. I followed the bleeding routine with the steering which works fine, but the pedal is still rock hard.

I removed the return line from the accumulator to the reservoir and no fluid came out with the engine running. I remove the line from the Pump to the Accumulator and ran the engine and the fluid just trickled out - I was expecting this to be quite a flow.

Is my PAS pump the fault here or is it something else?

[K Simmonds]

Welcome to the forum...

I'd have thought there should be a fairly significant flow of fluid from the pump to accumulator with the engine running... Though this not something I've ever tried so I could be wrong.

I would suspect it's the pump at fault, though a second opinion would be good to have.

[Tractor Dave]

If your power steering is ok I would suspect the brake booster.

[K Simmonds]

He say's he's tried two accumulators... I guess they could both be at fault.

What engine is in the car? I'm guessing a V6 given your user name.

[B4 Cab Simon]

I've only tried one Accumulator which was second hand but working when removed, although I appreciate that's no guarantee. It's the 1.8 ADR engine.

I did wonder about the booster, is there a way to test them?

[K Simmonds]

Is the ADR is the non turbo 20 valve or is it the 2.0 8V engine?

It's hard to test a servo other than try another one, though if they fail you'll still have brakes but have to press the pedal really hard.

[B5NUT]

It's the 1.8 20V none turbo. My A4 uses the same engine.

[Tractor Dave]

The accumulator only stores pressure so that if the engine fails at high speed, you still have brakes. After the engine has been running for 30 seconds or so the tandem pump should build pressure in the system and the brakes should work regardless of the bomb. The pressure is fed to the booster which converts that to additional braking force. So, either your tandem pump isn't producing the necessary pressure at the booster or the booster has failed. I seem to remember reading a thread on here a while ago detailing how to test your booster but I can't seem to find it.
I do have a spare booster here if you can't find one but I was keeping it as a good spare for my S2.

[Tractor Dave]

I can only find one on ebay.
https://www.ebay.co.uk/itm/Audi-80-9...edirect=mobile

[K Simmonds]

I have a couple of those spare, PM me if you need one.

[B4 Cab Simon]

Thanks all - following the recommendation I ordered one off ebay last night to try and get it this week, I really need to get back on the road. The plan is to get the Accumulator and Booster which I have removed from the car refurbished. I've seen some threads talking about a Citroen specialist who can do the bomb - do you know who that was? Also, is there somewhere that will service the servo? Thanks again, Simon