I am having an issue with the brakes on my 2000 Jeep XJ. After driving and using the brakes for a few miles the pedal gets stiff and the front brakes start dragging to the point you have to give it quite a bit of gas to move. My xj has 382452 miles. I have replaced the front pads, rotors, calipers, rubber lines, proportion valve, master cylinder, and the booster. The system has been bleed 3 or so times. Booster is getting good vaccum and lines are all in good shape. Once the brakes start dragging of you leave it sit for awhile it's back to normal until you drive a few miles. At first they feel normal until the pedal gets stiff. I am not sure what it could be at this point.

Thanks for any help with this. Would really like to get it back on the road.

 

The knuckles where the brake pads ride usually get divots in them and can cause this. You can weld them and grind them down. I've done it on mine. Works great.

Edit:
On second thought, this sounds like an improperly adjusted brake master cylinder pushrod. You need about 1/2" of pedal freeplay.

There's a vent port in the master cylinder that allows fluid to expand back into the reservoir as the calipers heat up. If that vent port is covered by the piston (because the pushrod is too tight) then this EXACT situation can occur. The fluid expands, the brakes get hard, and it slowly locks the wheels up.

 

 

I had that issue with the Mustang after replacing the booster. Brakes were fine for a couple stops, and then it struggled to move. Front brakes wouldnt release. That pushrod was the problem. Too long.

If you still have the old booster, measure the pushrod length and adjust the new one to match.

 

I messed with the rod adjustment. Tried it several different ways to all the way in and same issue. I do not have the old parts anymore. Is there a process for a measurement to take from the master cylinder to transfer to the booster push rod? Thanks again

 

You should have only shortened to rod. Nothing else.
Stick some clay into the back of the master. Bolt the master and booster together.
Disassemble. See how thick the clay is or isn't. Should have 3'16" or so.