Brakes Dragging, tried everything!!

[ecotec38]

Hi all,

I have a 97 model vs commodore with abs and recently out of the blue all 4 brakes have been dragging after
a short while of driving, it doesnt do it when you first get into the car its only after about 10-15 mins.
I have:
- Replaced booster
- Changed master cylinder with one i know is working properly
- Changed ABS module
- Checked all brake lines for kinks or dints
- Got new fluid and bled it numerous times
- Checked and replaced little one way valve that goes into booster

Now heres that part that gets me, once it has started locking up, sometimes to the point where its barely
even driveable because they are locked up soo bad and i pull out the little valve that goes into the booster
so it releases all the vacuum or pressure and the cars brakes will free up.
Any ideas?

[Deltak]

Hi,

It could be that one (or more) calipers have dirt/rust caught between the piston and the caliper - which can hold the pad on. With the car out of gear, released Handbrake and chocked in place, jack each wheel up and see if it turns easily. This will tell you if it is all brakes - Master cylinder etc OR only one brake - ie the wheel cylinder.

If it is one caliper, push back the piston and then pump the brake pedal to move the pad back on the disk.

[88GreenVN]

Have you greased the sliders on the calipers? you should be able to move them by hand when you have them apart. (pads out)

[ecotec38]

I have checked all the wheels and they all turn fine... when the car hasnt been for that short drive, i also replaced the front pads with new ones and greased the slides, the car drives absolutely perfectly for the first 10 or so minutes but after that short amount of time when vacuum builds up in the booster or brake fluid gets hot or whatever happens it just starts to drag until it gets to the point where you can barely even drive it anymore. The wierdest thing for me is when they are jammed on all i have to do is release the vacuum pressure from the booster and the brakes free up

[Cheap6]

Because it's all four brakes and you can free it up by breaking the vacuum to the booster I think it's going to be something in the area of the pedal, booster or M/C.

Carpet snagging the pedal?

Perhaps a brake light or cruise control switch is holding the pedal down?

Worn and sticking pedal pivot bush?

[Tree cutter]

Check that the return spring on the pedal has not broken or slipped off.

[greenacc]

Silly question time, If the engine manifold vacuum creates vacuum in the booster through the vac hose, and vacuum is somehow released or lost when you apply the brakes ( otherwise you would not need a vacuum line because the booster would hold vacuum forever.... ) it seems your system is holding too much vacuum !! Did you put the valve on backwards or something ? was any work done to the brakes or engine before this trouble started ?

[ecotec38]

Nope i dont think it would be them, as said earlier its fine for the first 10 or so minutes.

Return spring is fine.

Nope literally hadn't opened the bonnet for like a month and then all of a sudden this happens, very strange

[Not_An_Abba_Fan]

Check the one way valve that connects to the booster, it is the little plastic attachment that the vacuum line attaches to that goes into the booster.