philwarner

Yesterday driving my 1996 Gnd Cherokee V8 I reset the MPG on the trip computer and noticed it started at 22 and then slowly dropped while driving 50 on a two lane road, and when I got on the freeway I felt an unusual vibration at 60 and when I slowed to get off the freeway the brakes juddered and smelled hot. When I got stopped the right front wheel was hot and had a lot of brake dust on it, so I assumed the caliper was sticking (like I had experienced on both of my Plymouth Voyager vans), and I figured I'd let it cool down while I ran some errands on foot. An hour later I started the engine and heard a loud whoosh when I stepped on the brake peddle that seemed to come from under the dash directly in front of me. I still had some braking, but no power assist, and driving carefully home the whoosh sounded with each push of the peddle.

I'd used this Gnd Cherokee a few days before to pull my boat and there was no unusual brake action then, but that was only a mile or so at low speeds (and, no, the wheels did not get into any water). BTW, the ABS light has been on since I've owned this Jeep, but not the red brake light and the brakes had always behaved like normal non-ABS brakes. All the ABS sensors check OK so the ABS problem is somewhere else and the red brake light is still off if the hand brake is off.

So.....are the hot brake and whoosh part of the same problem? Or just a coincidence? I did not hear the whoosh until after it sat for an hour, and while the wheel was too hot to leave your hand on, it was not valve stem cap melting hot like one of the vans had been when its caliper stuck. What is the first thing I should check?

philwarner

Forgot to mention that no codes are set and the right front wheel turns relative freely back and forth by hand with just a little sound of pads rubbing rotor after sitting overnight.

jakbob

I would say the lack of power brakes would be the brake booster.

philwarner

Yes, I figured that too since the whoosh is loudest at the inside of the firewall where the booster link comes through, but I still wonder if an impending booster failure could also make the right front caliper drag. Seems really odd that both things happened almost at the same time and are on opposite sides of the Jeep.

I noticed this morning that when I push the brake peddle at idle the engine momentarily speeds up and then drops back; it must be getting lean from the vacuum leak and then the computer is compensating, but the Hg reading on my Actron doesn't change much when it does it.

dave1123

I'd say you have two problems. The brake booster is leaking and the caliper pins on the front brake are sticking. Replacing the pins and rubber bushings is easy and inexpensive. The booster is a PITA and not cheap.

philwarner

I did replace the booster and I agree it was a PITA, especially when someone had rounded off one of the two nuts hidden under the thin metal bracket holding some of the ABS stuff to the MC. Had to force vice grips in there and then replace both the thin nuts. The booster will come out without disconnecting any brake lines, but not without a fight. I'll check the RF caliper when the rain stops.

dave1123

I had this problem on my 97 ZJ after changing the brake pads because the pins moved to a location they were stiff in. I replaced all 8 pins and bushings to be sure I wouldn't have this problem again. I found I had to jam a thin screw driver in to break the bushings away from the caliper bores because of the rust. Then I used a steel brush to clean the bores and lubed the pins with high temp anti-seize. Lots of labor with a small cost for parts. Because I'm 68 years old and have a bad knee, most of the hard part was moving the jack and taking the tires off.

philwarner

I had to drive my 96 GC to pickup a trailer before I had a chance to check the RF caliper and guess what? No dragging of any brakes with the new booster installed.

I had wondered if it was just a coincidence that the booster started leaking right after the brakes got hot, and apparently it was not a coincidence and a failing booster can partially apply the brakes and the right front just happened to get hotter than the left.

I would never have thought the booster was the cause if it hadn't started whooshing.

dave1123

I'd still check your pins. It could be the heat loosened them up.