brakes locked

[jackwdwyer]

hi, yesterday my brakes decided to lock up while i was driving at first they felt like they were grinding, so i stopped, and when i tried to get going again the brakes were completely locked. It kind of fixed itself somehow a few minutes later after fiddling with the pedal and i was able to drive home.

It did the same thing today and all four wheels are locked. The pedal dont feel right either. It feels like there is no resistance where the brake pads would ussually hit the disc and you would feel some resistance. The pedal goes down really easily and then when its stops it feels really solid. It is as if when the brakes was pressed, the pads pushed against the disc and then when the pedal was released the pressure in the braking system did not release, therefore the pads did not retract. Is there something in the brake lines obstructing fluid? Or do i need a new master cylinder or anything else? Thanks in advance,
Jack.

[FierySphere]

Sounds like a seized brake piston in a caliper. Time for a rebuild, or replacement.

[jackwdwyer]

Is it correct that all four calipers could be seized?

[dfyoung10]

There is a check valve in the master cylinder that allows you to pump the brakes and accumulate pressure. That might be stuck or dirty. Also maybe something to do with the ABS. Is your ABS light on?

[s0crates82]

There is a check valve in the master cylinder that allows you to pump the brakes and accumulate pressure. That might be stuck or dirty. Also maybe something to do with the ABS. Is your ABS light on?

a better question is "does your abs light come on when you start your car"

mine doesn't. :(

[jackwdwyer]

the abs light does not come on, is there any way of relieving the pressure or checking the mastercylinder without loosing brake fluid and having to bleed the brakes?

[dfyoung10]

The pads never really retract; they are always slightly rubbing against the disc rotor. If the pads in all four calipers are actually locked against the rotors when you are not pressing on the pedal, there is obviously unrelieved internal pressure in the system. You can real quick crack and retighten a bleeder screw; if you do it quickly, air will not be drawn back into the system requiring bleeding. Then all the calipers should be loose enough to turn the wheels.

But if you take the master cylinder apart, you will have to bleed the system. It's really not that hard to do. Look in Bentley or any decent car manual; it's the same process in most cars.

Look at the rod that connects between the brake pedal and the master cylinder. See if when the rod is retracted with the pedal back in its normal position if the internal piston that the rod pushes against is still sticking deep inside the cylinder. If it is, it almost has to be a bad master cylinder.

[jackwdwyer]

thanks dfyoung10, i will check the pedal and rod tommorow when i can get to the car, (its at my college car park at the moment). What you said makes sense because that is what it feels like when you push the pedal, like the internal piston is stuck inside the cylinder. Do you know if this can be repaired, or shall i start looking for a new master cylinder if this is the problem?
Thanks,
jack.

[dfyoung10]

It's not so much hard to rebuild a master cylinder as it is unforgiving if you do it wrong. And they aren't really all that expensive. Better to replace it.