searchin99

Replaced the master cylinder and the front wheel cylinders/calipers, bled the system, and now there seems to be an air leak in the system that wasn't there before. All parts replaced were genuine new Audi parts (from an Arizona advertiser on this web site and not rebuilt or aftermarket.

The brake pedal gradually goes down over a period of a few days and after bleading the lines, starting with the rear first, there is lots of pedal, but the problem repeats itself.

Calipers: I'm positive that the brake lines into the wheel cylinders (calipers) are good because they are fine threaded and there was no problem screwing them in.

Bleed screws: The bleed screws all seem good and tight and work okay.

Master cylinder: This is the one I'm a little concerned about and the bad part is it was very expensive. The lines going to the master cylinder look okay from the outside but there was a tad bit of a problem geting them screwed in easily and I was careful to avoid crossthreading. Looking at the threads they look okay and don't look skewed as if they could be cross-threaded.

The other issue, don't know if it is related, but according to the manual there is a particular method to bleeding the system and I didn't understand it fully so did it the way I have usually done it with the engine running and my wife slowly pressing on the break pedal while I did the bleeding using a clear plastic hose into a jar (closing the bleed screw when the pedal went up) until there were no air bubbles. End of hose was submerged in fluid.

Does anybody have any ideas on how to determine if it is an air leak or, if it is, how to find it?

Something other than try replacing the master cylinder!

Thanks.