Break pedal hardens...? help!

[Bricstar]

Hey there, so i have been getting this "problem" with my breaks over the past couple of weeks... and i thought i'd ask people here if they know how to go about fixing something like this.
90% of the time my breaks work as they should, ( nice spongy feel to them when pumping etc) but every now and then when i'm driving i can feel the break pedal getting harder and harder and there have been quite a few times where the pedal has gotten so hard, i can't press down on it anymore. as it tightens up, i can feel a lot of resistance on my car and this gets worse and worse as i drive to the point where i have to pull over and let it chill out for a bit. (having to drive in a 50k zone in gear 3 because 4 just doesn't have the pulling power!!) its a scary feeling, and i don't know whats going on because like many other avenger problems, the come and go and you sometimes never knew what "fixed" them..

after the breaks tighten up, I walk around the car and can smell melted break pads and the front two mags are pretty hot. about 45 minutes later i can jump back in and drive off normally,
so i know that its something to do with pressure locking or even an old valve playing up in the break booster...?

i have taken the front two wheels off and lubricated the two pins that slide and hold the break pads but it happened again yesterday so i',m back at square one.

can anyone help me on this one?

thanks,
Jack

[oldschool]

That's happened to me too...a classic case of seizing disc brake caliper pistons. Fine when the brakes are cold and then expand with heat and stick. The calipers need overhauling with new pistons and seals fitted. My local Autostop branch did mine as it's a very hard DIY job to take them apart.

[NZTiger]

Another possible cause is that the master cylinder seals could be breaking down and chips of rubber are being pushed down the break line when pressure is applied, but when the pressure is released the chips get caught in the ports, blocking the returning fluid and therefore the pressure is not fully released and the brakes are held on. In the worst case all 4 brakes will be partly held on.
If your car is a Chrysler with dual master cylinder, this can also happen in the shuttle valve, I had this problem and the rear brakes were being held on.

[Paddy75]

Seen something like this on a '75 1600 I've worked on. By the sounds of things the calipers are binding and its a common enough issue with early disc brakes.
Watch out also for the hub grease puking out of the rear hub seal if the discs are getting really hot. Re-greasing the hubs after brakes have overheated is a good precaution as is fresh grease after 40 years of damp and dirt.
The way I freed up the seized calipers was to remove them from the hub and got an assistant to carefully push the brake pedal until the piston was about to come out. Pull back the rubber dirt shield boot and clean the piston best you can with brake fluid. Wipe the piston dry and then hold the caliper upward so that you can allow clean brake fluid to sit around the piston seal, that's the main hydraulic seal I mean to say.
Next push the piston back into the caliper as far as you can, if using a G-clamp be careful not to distort the piston sideways, put a washer inside the piston hollow if this keeps happening.
Just keep pushing the piston in after your helper has used the pedal to run it out to the end of its travel and lube with brake fluid each time.
It will likely take 10-12 goes before the caliper frees-up. A pain of a job but short of getting new calipers its the only way to do it. When you are finished smear a little, and I mean very little, grease on the piston's side.

Re-fit the caliper and bleed the brakes. Finally if you can get the old asbesdos brake pads then use them and just be careful when working on the brakes. Carbon based linings tend to mess up the discs as the contact area is too small to deal with the heat carbon linings generate.

[JoKer]

hm suffering sticky caliper myself, second guessing a road trip at the end of the week, I may try swapping calipers