Why have both front brakes seized up on my 1999 Jeep Grand Cherokee???

Question

The brake pads were changed about 1 month ago, but until yesterday, the truck was driving fine. Now all at once, both front brakes have seized up and I'm trying to figure out why. It doesn't make sense that both calipers would fail at EXACTLY the same time. My father suggested that the master cylinder is bad, but I don't want to jump to conclusions...

Has anyone ever had this problem before? What should I check first? And if all else fails, how can I be positive that the master cylinder is bad?

The metal brake lines were recently changed and flushed by the dealer, and there is plenty of fluid in the master cylinder. Any and all opinions are very much appreciated!

Thank you in advance.

Answer 1

This happens alot. DOT 3 brake fluid absorbs moisture over time a corrosion ridge forms on the caliper bore and or piston. Water is heavier than brake fluid and falls to the lowest point in the system. When you push the caliper piston back to install the new thicker pads the piston seal is now riding in the area of corrosion. The seal can only flex so far to release.  The brakes "sieze" because the piston is stuck in this area of corrosion instead of being free in the bore.. Crack the bleeder, if the piston presses back easy it is a brake hose, if it still wont press back it is a caliper problem.

Answer 2

Please add more to the definition of "siezed up".  I have had a similar problem in the past.  When you apply the brakes, they seem to drag, heat up, and smell like burning.  It took me a long time to figure out that the problem was the rubber hoses that go from the metal lines to the wheel cylinders.  The lining deteriorates and debris from this acts like a one-way check valve.  Fluid pressure that applies the brakes gets trapped in the cylinder and keeps the brakes on.  Bleeding the brake lines doesn't help.  When the bleeders are cracked open, fluid squirting out under pressure is an indication that this is the problem.

It is most likely not the master cylinder.

Answer 3

bleed them then change master cylinder

Answer 4

that is pretty suspect.  Check for any recalls on that.  I had a 97 and got new rotors for free from a recall.  Just trying to save you any money i can.