can some please help me figure this out ? 2002 Audi Allroad 2.7 gas motor , my front breaks are overheating I checked the calipers and the pads they are good and work fine the breaks fluid looked like a green gel so I bled it all out and replaced it with new DOT 4 and I bled all the breaks I though I fixed the problem but after driving the car for a couple days they are still overheating , could it be the master cylinder , the ABS or maybe the vacuum assist . the back breaks are fine with no issues thanks