front brakes locking up - 92 bonneville

Hi,

I have a 92 bonneville. We've had a lot of repairs done, and the front breaks are locking up

while driving, after braking to slow or stop.

Some background: the brakes lost pressure, and we took it to a dealer. They ran ABS tests, and

this showed the ABS had problems (sensor, pump), but the reason for lost pressure was probably

master cylinder and rear brake seal. We had the dealer do the rear brake seal, which did not

fix the lack of braking pressure. We took car to PEP Boys to have master cylinder done (to save

money as dealer was so expensive).

We decided to do without ABS, as it would be up to $2,000 to repair it.

PEP Boys did the master cylinder, and replaced the brake lines which they said were leaking. We

now had brake pressure again, but after driving the front brakes locked up. (Either both or

one, we were not sure). Back to PEP Boys and they said the right front caliper was locking,

probably due to the cylinder in it, and said we had to replace both calipers and the flex lines

leading to them. We had that done but the front brake(s) continue to lock up.

Back to PEP boys and they now say they think it is a problem with the ABS system. We disagreed,

stating this happened after the master cylinder and lines were done, and the brakes never

locked up before. PEP Boys says it might be the ABS pump, which is dowstream from the master

cyclinder, and the BAS pump may be malfunctioning - but PEP Boys does not have the equipment to

test it!

I already know the ABS system was not functioning from the earlier dealer tests, but to

eliminate ABS as a cause, I pulled the fuse for the ABS system. The front brake(s) continue to

lock up. PEP Boys said to take car to a dealer and have them test it (PEP said they would pay

for the diagnostics, and redo any repairs PEP Boys did if the dealer says it is related to PEP

Boys work). So it seems we paid for calipers we did not really need.

I called the dealer, and they said to bring it in, but said it is unlikey that the ABS system

is causing the brakes to lock up. They don't know until I bring it in and they look at it - but

suggested over the phone that it might be related to the booster, because when the brakes lock

up one of the symptoms is that the brake pedal stays in the upright position, and is firm and

can't be pressed down.

Anyone have any tests or ideas as to fixing this problem? Does the booster seem like a culprit?

We are already out about $700 on all the repairs to date.

Thanks,
Matt