sudden loss of breaks

[johnny boy]

Hi guys , Well i have had a small problem with my brakes 4 a while every time i turn the car on the dash beeps and the brake pedal is solid the brake sign flashes red and after about 30sec or so the light goes out and pedal feels normal , i drove the car the other night and pulled up at some trafic lights and the pedal went to the floor with very little stopping power in fact there is none , i have had a look at the brake fluid level and all is ok , i have a sneaky suspicion it could be a pressure accumulator but having the mechanical knowledge of a potato i dont konw any suggstions boys

cheers johnny

[Ski]

maybe the big bomb?

[Baldy]

dont know if the bomb test sequence is the same as on UR quatt but on a UR its this:

Start and run the engine for a minute or so.

Stop engine.

Apply the brakes - press the pedal hard (Audi say 'same force as an emergency stop'). Count "1".
Apply the brakes again. Count "2".
Repeat (counting number of applications) until the pedal goes rock hard.

If the number of applications approaches 40 then your bomb is ok.
Bout 20 is Dodgy
Less than 10 is dangerous

[Doug_RS2]

Sounds like 2 problems. Hard pedal is the bomb.

The other problem sounds like a leak or master cylinder seals are gone.

Park the car on a dry road and pump the pedal and push on it hard - does it go to the floor? look for leaks of fluid around brakes, on the wheels and on the ground. You have the RS4 wheels? Do you have new brake lines on your brake setup? Are they flexis rubbing on the rims? Check the condition of all flexi hoses.

HTH

[johnny boy]

hows it going boys all the break lines have been changed braded hoses ect i`m sure the bomb was changed as the reservoir is new but will have to check recipts , i will do the break checks when i get home , if it is the big bomb is it an easy job to do ??

cheers johnny

[johnny boy]

Just checked it was a brand new master cylinder ..

[Mikes2]

Check the PAS hydraulic fluid level and make sure the fluid in there is green and not red

[Graham]

For the pedal to go to the floor, i agree with Doug, it must be the master cylinder. If the bomb/pump fails the pedal just goes hard and you have to nail the brakes really hard to stop, but if the pedal goes to the floor, it can only be, 1)somehow a pad has broken up and the master cylinder has to take up the slack till it has contact with the disk and works again, 2) a massive leak in both pressure lines (if one fails the other will still provide assistance, 3)Master cylinder seal has split/folded and leaks internaly providing no pressure. Dont forget that an object is most likely to fail within either the first few weeks/months, or at the very end of its usefull life when its worn out. This last one is the most probable.
HTH
Graham

[scouser_75]

Johnny,

I have defo found that these kinda things on S2's always happen in groups - On saturday morning I got into my car, turned it on, and EXACTLY the same problem as yours. The brake pedal went straight to the metal as I was pulling out of my drive. At first as there were hardly any brakes to bring me to a stop! Followed by as the last thing I need right now is to splash out cash Checked the brake fluid reservoir and it was completly empty

But the problem was a simple one to fix. I recentely had my rear calipers replaced and the mechs just hadnt secured the cables properly. I suggest you check these too. A simple fix hopefully