Hello to all, I find my self in a very confusing situation. Basically my front calipers get stuck after about a mile or 2. Initially the brakes where just sticky, I rebuilt the calipers and not luck, still sticky. I then replaced all the brake hoses with Goodyear SS Lines and obviously bled all 4 brakes in the correct combination. And now after installing the lines and bleeding the system and driving about a mile or 2 they lock up completely and stay stuck..

I cannot figure it out, my next option would be to buy the calipers but im not too sure that will fix it. Please if anyone can help I will really appreciate it.

 

Rebuilt the calipers? Sorry to question your abilities, but this makes me worry.

I'd go find a set off someone's parts car and start over.

 

Are you using the brakes while driving that mile or two or just driving down the highway without touching the brake pedal? How do you know the problem is with the front brakes? Are you jacking the car up and checking them when it happens? Need a little more info to go on.

What year car do you have? The brake system has two circuits so you can't lose all braking at the same time. 97-00 the front brakes were on the same circuit and the rears were on a separate circuit. In 01 GM changed to dual diagonal braking so the left front and the right rear were on the same circuit and the right front and left rear were on the other circuit.

Bill

 

Just feel the wheel, the hot one is the one hanging.

 

I ran into the same problem on a C4, but it still might be the same issue. The C4 had a plastic booster housing. The plastic had deformed slightly causing the poppet valve in the booster to leak a little air into the rear half of the booster which allowed the vacuum in the front half to gradually apply the breaks without touching the pedal. We rebuild boosters and have seen that problem only a few times. The only solution was to replace the front and rear half of the booster can. You can test for this condition by removing the vacuum check valve and see if the brakes release. If the brakes release, the booster is your problem. If not, it's a hydraulic problem. Some brands of brake fluid will swell the rubber cups in the master cyl., so be carefull to use a good name brand of fluid. If thats the case, flush out your whole system and rebuild everything with new cups.

 

I apologize I meant I bought the piston rebuild seal kit and put new seals on the pistons inside the calipers. But yes I know for a fact its the fronts because both wheels are so hot after driving about 5 miles than if throw water at the rim and rotors, super hot steam comes off
(which I know is bad for the rotor but a new one is going in after the fix) when i lifted the car the front wheels will not move and inch only after they cooled down they were able to be moved slightly but still too tight. Just a couple of minutes ago I found that the pistons go back but only when I relive pressure by using the bleed valve on the calipers.


BTW I have a 2000

 

Have you used the DIC to see if there are any codes? Are there any warning lights lit on the instrument panel?

Bill

 

Nope there is no codes at all. I even disconnect(unplugging the ground cable)the ABS module in the front of the engine to see if that was malfunctioning but still the same result. So it seems to be mechanical not electrical but I just confused at this point

 

Sounds like a booster problem to me.

 

Try plugging the vacuum going to the booster, you won't have power brakes for this test go get in a BIG, OPEN space. Apply the brakes several times and see if they hang up with no vacuum assist.

 

Back with an update I tried dougbfresh idea and the pedal obviously was super hard but the car stopped by it self anyways, because the calipers are stuck. This morning with the car dead cold from the night before I put the car in neutral (not turning it on) while it is sitting on a steep slope, it doesn't even move back an inch . I just going to replace the calipers bleed the system once again if that doesn't work im jumping off a bridge lol

 

You have a bad proportioning valve. Just off the master cylinder is a little metal block that contains the proportioning valve. My guess is yours went bad and is locking up the fronts.

2001 and up vettes have the proportion valve built into the ABS block.

 

Update: I have replaced the calipers and still no luck they front brakes lock up. Now when I went to bleed the brake the rears did not bleed . I believe I need a new proportional valve but from what I have researched the proportional valve goes in the rear but what is the combination valve is it the small valve the goes between the master cylinder and the ABS module? I got this from Mid America's website it says it the combination valve but it doesn't look like the one I have in my car and mines is a 2000

 

^ That looks like a proportioning valve to me.

Why did you not order the part from a dealer ?

 

I haven't called the dealer yet but I did check GMParts Direct but they don't have a image nor a diagram of how it should look.

 

Post a picture of what you have. The picture that you posted above is a proportioning valve. It is in between the ABS and Brake Master unit on dirvers firewall.

 

All the times I've ever seen a proportioning valve fail it leaked externally.

 

Here is the valve, I ran a test on this by first testing the master cylinder and booster I disconnect one of the two lines on the cylinder and fluid comes out of the cylinder when I press it, I did the same with the second line so it is not my master cylinder or booster. I then reconnected them back and proceeded to the valve below I disconnect the bottom out port and no fluid came out when I pressed the brake. I then disconnected the top in-port and obviously fluid came out the line going in but no fluid came back up when I released the brakes. Basically the brake fluid is not traveling back and it seems to be this valve, well I really hope it is.

BTW the valve seems to have a part number on it and when I input that number in gmpartdirect parts search it says proportional valve.

 

Does anyone know what part of the brake system pulls back the the brake fluid back out of the calipers??

 

The brake system works this way.

The master cylinder (where the brake fluid) under the hood is located is called the master cylinder.

Your foot pressure at the brake basically, compresses the fluid in the system and applies your brakes by pushing the fluid (applying pressure). Once you relieve that pressure by lifting your **** off the brake pedal the fluid pressure decreases and thus the brakes are no longer applied.

Leaking vacuum pressure at the booster can cause problems but typically it effects all (4) calipers not just the front.

The picture of the valve you showed was a proportioning valve, however GM used various.

Proportioning Valve Description
The proprotioner valve includes two valves which are in-line with the rear brake pipes and limit the hydraulic pressure to the rear brakes after a predetermined master cylinder pressure has been reached. The proportioner valves improve the front to rear brake balancing during normal braking.


Hydraulic Brake Diagnostic System Check
Step
Action
Normal Result(s)
Abnormal Result(s)*

1
Inspect the master cylinder brake fluid level.
The brake fluid level is nominal.
The brake fluid is low.

2
Turn the ignition OFF.
Ensure that the park brake is released.
Start the engine.
The brake warning indicator turns on while the engine is cranking.
The brake warning indicator turns off after the engine starts.
The brake warning indicator does not turn on while the engine is cranking.

The brake warning indicator stays on after the engine starts.

3
Shift the transmission into Park.
Press the brake pedal firmly.
The brake pedal moves steadily towards floor, approximately 50 mm (2 in).
The brake pedal stops and is firm against the pressure.
The brake pedal does not move steadily (hard pedal or pedal moves erratically).

The brake pedal is too soft (travels too far toward the floor).

4
Release the brake pedal.
The brake pedal returns to the original position.
The brake pedal does NOT return to the original position.

5
Perform the brake system test.
The braking action starts immediately after applying the brakes.
The brakes operate smoothly and predictably. do not grab - brake pedal does not pulsate.
The steering wheel and the brake pedal do not shake (pulsate) while the brakes are applied.
The vehicle stops without high brake pedal effort.
The vehicle stops without pulling to one side.
The front and rear brakes apply evenly.
The brakes operate without excessive noise.
The brakes do not drag (stay engaged) after the brake pedal is released.
The braking action is delayed after applying the brakes.
The brakes operate aggressively with low pressure applied to the brake pedal.
The steering wheel or the brake pedal pulsate while the brakes are applied.
The brake pedal effort is high or the vehicle is difficult to stop.
The vehicle pulls to one side while braking.
The front or rear brakes operate unevenly.
The brakes make noise.
The brakes drag (stay engaged) after the brake pedal is released.

* Compare the test results with a like vehicle that is known to be operating properly in order to verify that the test result is abnormal.
Refer to the appropriate symptom diagnostic table for the applicable abnormal result.