Jeep Wrangler brakes drag after 1/2 hour of use

I have been having a brake drag problem with my '89 Jeep Wrangler. I posted this problem previously when I thought it was an E-brake issue. I appreciate the response,and did a rear drum spring set change. The problem persisted, so I asked the local auto parts store and they said it could be a faulty master cylinder which I just replaced. The brakes felt fine for the first 1/2 hour driving, then the pedal started feeling harder to push and the brakes were dragging again. I jacked the car up and removed the tires to find both front calipers tight on the rotor, the rears would spin. With someone pressing the pedal, I did not notice any caliper movement.

Any suggestions ?

Try opening the bleeders on the calipers. If it frees up the rotors the rubber hoses to the calipers may require replacing.


Have you adjusted the vacuum booster? These are non adjustable and should only be replaced. If the booster is pushing on the master, it can cause a brake drag.

ComfortEagle’s idea can also be tested by pumping the pedal with the engine off. If the booster is the cause, pumping the pedal will release the residual vacuum on the front side of the diaphragm and the wheels should spin free.

And if per chance you HAVE adjusted the booster, then you have a good place to look for the cause.

Thanks…I just bled them and the discs freed up…although the fluid did look dirty. I then had someone pump the pedal while I spun the hub and the calipers seem to be working on/off fine. There is a rubber hose that runs down to a metal tube that is bolted on at the bottom inlet to the brake…it looks like one piece. Everything is rusted badly so I can see this is not going to be easy. Thanks again…

Thanks for yours and Comfort Eagle’s reply…, I only replaced the master cylinder…I did not touch the vacuum booster. Before I bled the fronts today, I did pump the pedal a few times to check for caliper movement, but they were still tight after a few pumps…but it may have required more pumps for your test.