I have a 2000 A4 Quattro on which I just installed rebuild front calipers, but I can't get all the air out of the system (poor pedal and no fluid out of the bleeder with pedal pumped and held). The calipers were off the car for at least a full day or two for cores when picking up rebuilt ones, and alot of fluid ran out of the left front brake line. I suspect the ABS pump is dry, which seems to be supported by a lack of fluid seeping out of at least one line when trying to bleed at the pump. The brake light is also on after starting the vehicle. The problem seems concentrated on the left side, as the RF looks to bleed fairly well. I've even tried the vacuum pump bleeder approach at the calipers. I called my local Audi dealer and the service advisor said I need to have it towed in to be pressure bleed with a machine, I also saw a mention on the internet of a command typed in via a piece of test equipment that instructs the ABS unit to purge itself of air. My questions are 1) does everyone agree a dry ABS is the cause of my problem, and 2) is anyone aware of a trick that I can do at home before I call to have the vehicle towed? Thanks

 

I dont think your ABS will be dry and even so your brakes don't run from the ABS, they run from the brake master cyclinder.

Go and buy some brake fluid and re attach all the hoses, then fill up the brake cylinder, undo one hose and get the person in the car to pump, pump, pump and hold brake pedal on floor while you do the hose back up. Tell them to release, do that to the other front then the backs. The pedal should be then very firm.

You normally repeat this process 2 times on each wheel.

Make sure you keep topping up the brake cylinder otherwise you'll suck more air in to it.

 

I've tried pumping and bleeding from various areas for many hours with no luck. The master lines go directly into the ABS unit and out to the calipers from there, I get fluid when bleeding the lines going into the ABS, but not out of.....

 

Oh, and I've always made sure the fluid reservior was full, but it doesn't seem to ever go down.

 

If you haven't done so already you may try bleeding with the engine running. I've seen that work sometimes, but from what it sounds you may have to go to the stealer so they can put it on the machine if you got air in the abs. or, check around with independent mechanics some may have that equipment. good luck.

 

I thought the ABS was an electronic system that required the engine turned on? I thought that was standard procedure? Sorry I didn't mention it before. I don't even know if thats right, but thats my logic.

 

Believe it or not, the most common reason for not getting the air out of a caliper change is because the left and right are swapped putting the bleeder down instead of up. The caliper keeps a bubble of air in the top. Not sure about the A4 but most calipers can be installed on the wrong side.

 

The calipers are on the correct sides with the bleeders pointing up and I have tried bleeding multiple times with the engine running and off. I even tried attaching the vacuum bleeder directly to the brake hose after disconnecting from the caliper, but still no fluid. A friend in the parts room at my local Audi dealer asked a couple of his mechanics and they said to start bleeding from the rear calipers first, even if I didn't disturn them. I guess a valve inside the ABS may have been shuttled over if just the front line had no pressure (?). I will hopefully try that tomorrow, yes the car has been laid up for this for many days now - Audis, what a pain.