90 Audi 100 locking up

Im trying to find out what my problem is here, before spending another 200 bucks just for the shop to replace brake pads. First of all, the car had been sitting for a long time. I was having problems with the
alternator not lining up and therefore it was going through v-belts every 10 miles or so. so anyways, got that fixed and seemed to be running great. I went for a little test ride and got about 10 miles away, parked at the bank, and noticed a white smoke coming from my tire. I drove home immediately and the entire way it just felt like the brakes were constantly applied. The second I would let off the gas, it would drop about 5 mph, and keep slowing down. So anyways, i bring it to the shop, they said they couldn't find any reason for the problem but they did replace the pads and rotors and completely bled the entire system. I drive it home and seems to be going great!!! I get up in the morning and decide to take it for an extended test drive. I get about 15-20 miles out with no problems whatsoever.. brakes seem to be working as they should. No soon as I said that, I feel the brakes lock up again. I find my way home, pull off the STEAMING HOT WHEELS... and verify my concern.. The brakes were indeed locked up.. you can see the the outline of the pads on the rotors! We took the pads off, and it seems like the calipers are working fine.. Again, this is on both sides... Also, the rears are extremely hot too.. We haven't taken off the rears, but they are also extrememly hot, however not nearly as hot as the front. So what do you think?? Probably the master cylinder??? Also, if it is the master cylinder, i was looking at them on advanceautoparts and there are some with a girling master cylinder, and some for an ate master cylinder... how can i tell which one i have??? Thanks for all your help, my mom is begging me to get this fixed so she can have a vehicle to drive!
-Dylan
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The only thing I can think of is a broken spring in the master cylinder. Since all 4 brakes brake, it must be the first spring.
Ronald
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If it would only be 1 brake that locks up then it was easy... But if all brakes are locked at the same time I cant think of anything else then the master cylinder.
In the ETKA (audi/VW database) I find 4 master cylinders for this car, 2x girling and 2x ate. On the original master cylinder there must be a VAG number.
The 4 possibilities: 893 611 021B: Girling 893 611 021A: Girling for systems with ABS 893 611 021 : ATE for systems with ABS and powersteering 441 611 021A: ATE for heavy-duty brakes
I hope this helps abit.

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I just wanted to say thanks for the quick help you guys! I think I'm going to go ahead and take my chances replacing the master cylinder. I've done it before on my 86 Bronco and that was a pretty straight forward job. Do you know of any tips or anything I should look out for?
As for the VAG number, I found one that is very similar. My car does have ABS and I also have a seperate powersteering resivoir. The number I found on my Brake resivoir was 893 611307A I'm going to assume I'll need p/n 112568 from advance.. http://www.partsamerica.com/ProductDetail.aspx?mfrcode ĄC&mfrpartnumber2568&parttype#0&ptset=A
Thanks again for your help.. this thing runs like a champ once its on the road... I've just been having a hard time keeping it there!
-Dylan
The Al Bundy wrote:

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Bleeding: The regular method of pushing the pedal and releasing the bleeder valve works but a vacuum bleeder is the best method.
The MC is right behind the radiator fan and they get hot. If you want to test it again, take a bottle of cold water with you and drive until the brakes drag. Get out and pour the water over the MC. If this corrects it this is your problem.
DiLLY wrote:

http://www.partsamerica.com/ProductDetail.aspx?mfrcode ĄC&mfrpartnumber2568&parttype#0&ptset=A
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