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1997 Pontiac Grand Prix, No brakes on Left Front and Right Rear. Brake pedal goes to floor, not loosing fluid as far as i can tell. On the dash the Brake light is on. Have tried bleeding the system, getting no fluid to the two wheels not working. Also tried to bleed the “ABS” module? There are two bleeders on the ABS module, one i get fluid out of while the other no fluid. Any help, suggestions, or comments…
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May be a bad master cylinder… sounds like the internal seals are being bypassed. They are designed that each of two sections in the MC controls one each front and rear brake…
If you replace, ensure you bench bleed the MC, use the tubes (most usually included with the new MC) and keep pressing the piston until both tubes run clear with no bubbles in the brake fluid…
-Karl
I was thinking the MC might be bad, but I also have a feeling that ABS module might be bad… Maybe tomorrow when i get back to work I will change out the MC. Thanks
The hardest thing with your situation is the fact that GM used several different abs units on those cars. They all work a little differently. You didn’t say how this whole problem started but the first thing I can suggest is to make sure you have fluid pressure at both lines from the master cylinder at the ABS unit. If the master cylinder is defective you won’t get fluid to 2 of the wheels.
Not sure how the problem started, a friend of mine bought the car “as is” and it came with this problem. The brakes work on the other two wheels, the pedal just goes to the floor with ease, and pumping the pedal does nothing, just same result going to the floor. I am pretty sure he said he has to keep adding a little fluid here n there and I can not find any leaks. So I was leaning towards maybe it was leaking into the booster?
When you have to add a little fluid now and again, a good place to check is the back of the MC for a rear MC seal leak (it can be leaking wheel cylinders as well). This gets sucked up in the Vacuum booster or drips down between the MC and the booster….. I Just replaced an MC last week on a Toyota that had this issue… It had to have fluid added once a week….
-Karl
Leaking into the booster is possible but not likely on a GM. Another thing that comes to mind does the ABS light come on when you turn the key on? Can you hear a “clickity-clack” from under the hood when you turn the key to run position? Odd question but it might give me a clue as to what ABS system is on the car.
I cant remember for sure if the ABS light comes on when the key is on, but I def have not heard any sounds coming from the ABS module. The ABS module is really close to the Master, just off to the right, and down a little. This motor is the 3800 supercharged..
I think I know what system is on the car and if it’s not working that could cause the problem you’re having. Make all the other tests suggested and if ok start looking into the ABS issue if abs light is not working. Maybe a blown fuse or bad abs relay.
Based on your description I would say master cylinder. The system is split up where one port works one front wheel and one rear wheel on the opposite side of the vehicle. It’s called a ‘split diagonal’. The ABS would be expensive to get into at this point and I don’t believe it’s the issue here. I’d start with a master cylinder and go from there.
Keep us posted
I will be installing a new master tomorrow, so will let everyone know how it turns out for me. Thanks for all the help, this site is awesome and I am glad I found it!!
Ok I changed out the Master, and now everything is working great. Before I was not even getting brake fluid to the two wheels i had explained before, but I do now!! Thanks for all the input!!
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