Total Brake Loss '98 XJ Non-ABS

Ok, I should have done this months ago, but since the Fall is rapidly approaching and I've heard from two sources that the Farmers Almanac predicts a bad winter.........we need to get this fixed before it gets too cold out.

In January I was driving my '98 XJ after work, we had just put a new tires, radiator, water pump, theromostat, new #1 plug (haven't swapped the other 5 yet), new wires, cap, rotor and a few other things to try and get my XJ ready for last winter, I went to stop for a red light that happened quicker than I expected and pushed into the brakes hard, felt and heard some sort of POP and the brake pedal went to the floor while the truck started to roll faster......right through the now red light. I was able to get it home by manually shifting it and using the handbrake while it was in full time 4wd (it's an AW4 and Selec-Trac truck) to slow and eventually stop the truck as needed until it was home.

Right now all the brake pedal does is activate the brake lights and works the brake interlock on the trans so we can get into and out of park as well as into reverse. At the time the POP happened, the brakes were hard to depress and I had to put a lot of force into them before the failure happened, so it could be seized front caliper(s) that helped instigate it. The pedal seems to travel fine, but feels "disconnected" from the rest of the brake system at the same time. I have a friend that is a former GM Mechanic and now a newly minted automotive tech school teacher suggested it could have been the master cylinder seal failure that took the power booster with it, which had recently had happened on his '07 Silverado too. My Father is wondering if I somehow tore the booster guts apart while trying to panic stop. We will likely need to swap the front calipers, pads, rotors, and likely hoses (rears drum assemblies were installed in 2016 and still about 90%-95% new) anyway with how it wss behaving before this happened and back in 2018 when I had to get it through the Chicago Area emissions tests the last time. The only warning lights that are on are the "BRAKE" and "AIRBAG" lights, since the clockspring is dead too, and ones related to occasional voltage issues that Dad wants to try and throw a new belt at to see if that helps. I don't know if Dad ever checked the brake fluid in the master either, but he wants to try and pressurize the system to see if he can find any leaks.

Does anybody have any idea what we might want to look for while we start to dig into this?

I would check the master cylinder it sounds like a hose or btake line busted

If you haven't seen brake fluid all over something since January. then it's most likely the MC.

A failure of the booster wouldn't have the pedal drop to the floor. It might be the cause of the hard pedal though. I'd suspect a popped front brake line and rears not working, something in the linkage broken (I've seen the pedal connection break), or a complete failure of the master cylinder. Time to start looking at everything.

Thanks guys!

jeep ride said:

I would check the master cylinder it sounds like a hose or btake line busted

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Dad popped the cap off the master, it was empty:scared::scared:

Gave him flashbacks to the '90 XJ Laredo he had when it tore the rotors off the hats 20 years ago on his way home from work when he got cut off in traffic. He also drove it the rest of the way home too.

Pull the MC. Super easy. Pop the brake lines off. Booster likely bad too

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Thanks denverd!

Any recommendations on what brands to look at? I quite literally have pretty much every parts house here in town and within a few miles from home.

stock replacement is all you need. so then it's down to price and availability.

before you remove the clip holding brake pedal to booster plunger, test your booster with MC removed. if you hear a "whoosh" sounds when pushing the pedal, booster is bad. likely is anyway, just sucks removing the booster. I took driver seat out to gain better access to the nuts on they firewall holding booster in. if you have a small friend, definitely time to give them a ring. I couldn't get both hands under the dash at the same time. use some extensions and wobble joints or u-joints on your tools.

denverd1 said:

stock replacement is all you need. so then it's down to price and availability.

before you remove the clip holding brake pedal to booster plunger, test your booster with MC removed. if you hear a "whoosh" sounds when pushing the pedal, booster is bad. likely is anyway, just sucks removing the booster. I took driver seat out to gain better access to the nuts on they firewall holding booster in. if you have a small friend, definitely time to give them a ring. I couldn't get both hands under the dash at the same time. use some extensions and wobble joints or u-joints on your tools.

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Thanks again, my above mentioned and much, much skinnier, ex-dealer mechanic friend has offered to help if we need it and the seat needs to come out anyway. I have a dead power track that has the seat so far forward that my fat gut drags on the wheel and a manual track in the back of the truck that needs to be swapped in place of the factory part.