Help Me Stop!

I just recently bought a 1989 XJ with 100,000 km on it. My only major problem is with The ABS. Sometimes it works, sometimes it doesn't. I tried unplugging the ABS fuse "DON'T DO THIS" and it worked fine for almost a day untill I had to stop in a parking lot and there was no brakes at all. So I plugged it back in. It seems to kick on most of the time and when that happens you have to push pretty hard on the brakes to get it to stop. Then you get skidding and stuff. I'm not sure what to do and how to fix it. Could it be the main ABS computer? Anyone have a similar problem? Please Help.
thanks.hasta

Some of the earlier ABS systems used an accumulator and its pump to replace the brake booster. Bad idea, since now the ABS was integral with the brakes and NOT an add-on that could fail and the main system still work as designed. If the ABS failed, you lost the brakes or had extreme problems until you replaced the very expensive ABS parts.

Don't know if that is the case for your XJ, but check out the system, make sure there is Power Brake Booster that the Master Cylinder Mounts on.

ABS=absolutely bull s$$t (IMO)

Thanks
I will have to go and check the system this week some time, stupid snow.

Check on here for info. Put a M/C and Booster from a salvage yard 99 or so non-ABS. I put one in from a 99 Classic and my brakes work wonderful.

I think either 95 or 96 booster and mc (non abs) is a direct bolt-in for the Renix.

Sounds like I was right? The earlier Jeep ABS was the crap with pumps/accumulators from the ABS doing the power boost???

What in the world could they have ever been thinking? A $2000 ABS module, that if the highly stressed motor and high pressure accumulator leaked or failed, the entire brake system would malfunction. I don't know about Jeep, but the first ABS on the Mini-Vans was like this. There were so many lawsuits and warranty crap to come out of it, people were dropping $2500 a year to keep repairing their brakes again and again, and the only fix was too replace the $2000 module for the brakes to work again.

oh yea, also when i start up the truck it sounds like an air compressor is filling up under the dash. Could that be related?

I did the WJ booster/master swap. It's awesome. 89, no ABS.

call the dealership. The early bendix ABS system is covered under a lifetime recall for the pump .
the resons stated abofe are precisely why, if the abs pump fails they Jeep isn't driveable.

If it's within your means you might want to consider canning the ABS system and just going back to a regular master cylinder.

as to diagnosing your system:
The best thought would be to look at the basics.
fluid level - check this with your ignition key in the "run" position (engine doesn't need to be running), and allow the brake-pump to stop before looking at the reservoir - fill to the top of the "MAX" arrow. Most places are used to checking with the key "off" and that would cause them have not enough fluid in the reservoir bottle.

slow pump pressure - With the hand-brake pulled-up, start your Jeep and listen to how long the pump runs. The pump should stop in less than 4-minutes. Do not release the hand-brake or touch the brake pedal until the pump stops.
-- If the pump stops before 4-minutes, then your pump, actuator seals and the rest of the pressure system is in working order and you should look elsewhere.
-- If the pump runs for more than 4 minutes then your brake actuator piston assembly and/or the pump-motor assembly may be worn - these are the parts on the NHTSA recall. It's also possible that the relay controlling the pump and/or the switch controlling the relay could be bad.

computer fault - can't do much here without special tools - but on your '90, disconnecting the battery for 5 to 10-minutes may help clear the ABS computer's memory so you can start fresh.

bad/disconnected sensor - Look closely at all of the wiring associated with your ABS system -- the computer is underneath the rear seat on the left side of the vehicle - there are sensors at each wheel, and various connections to the pump, reservoir, distribution block, accumulator bloc, and stuff under the hood.

other - the Bendix system behaves oddly if you release the handbrake before the pump has built pressure - AND if you apply the brakes (foot pedal) while the system is trying to build pressure... if you ever drive with the hand-brake on, the computer also has "issues" (Most of these "other" items are related to the way the Bendix looks at the red "BRAKE" light on the dash pannel for input to some of its input)

and here's the NHTSA recall.

National Highway Traffic Safety Administration Recall 96V260000: ABS Hydraulic Pump Failure
relates to: Chryser recall notice #702

Vehicles equipped with antilock brake system (ABS).

Antilock brake system (ABS) hydraulic control unit can experience excessive brake actuator piston seal wear which could cause pump-motor deterioration.

If this occurs, the ABS function would be lose and reduced power assist would be experienced during vehicle braking. The instrument panel warning lights will signal system impairment and the base manual brakes will remain functional.

Dealers will test the vehicle's ABS and repair as necessary. The warranty on all ABS components will be extended to 10 years or 100,000 miles (except for the brake actuator piston assembly and the pump-motor assembly which will have a lifetime coverage). Owners will be reimbursed for previous ABS component repair costs.

Owner Notification began April 24, 1997. Owners who take their vehicles to an authorized dealer on an agreed upon service date and do not receive the free remedy within a reasonable time should contact Chrysler at 1-800-853-1403. Also contact the National Highway Traffic Safety Administration's Auto Safety Hotline at 1-800-424-9393.

Even if the dealer will fix the ABS, they may still ding you for anything in the brake system that doesn't fall under the warranty. You'd still be left with a crappy design that leaves you with no brakes if the fuse pops. I vote for pulling it and getting a 95/96 booster and master cylinder. It's a pretty common upgrade from the non-ABS Renix system which was a bit weak.

well i checked things out and it is pretty strange. the presseur seems to build up ok, but when i am driving you can hear the compresser kicking on all the time. BUT... if i lift up the e brake just till the light goes on I have no problems what so ever. I think i am just going to do the swap, what if any parts should i get or will need to do it? the master cylinder and booster swap. I saw a new one for 250 but i done know if that is a good price or not.

I also have a 89 XJ with the same prob. the dealership replaced the ABS part like 5 times in the lif of the jeep so far. It is acting up again so I need to give em a call one more time!

Yes if someone could tell me what parts i need to do this swap please help me out i would like to be able to stop one day........

I'm pretty sure that if you do a search, you'll find a number of writeups for swapping in a 96 booster and master cylinder. This is a common upgrade for the older Jeeps for better braking, but it also lets you pull out all the ABS crap.

I have done a search and have found nothing with a complete list of what i need to do this swap......

After looking around for my 91 I have come up with needing:

m/c , booster from a WJ do I need the prop valve also ? What else do I need?

Get all you can, even the brake pedal. I spent more time trying to get the frigging brake light switch adjusted than the M/C and booster install. I had to redrill my brake pedal a little lower to lign up with the rod. Yes get the prop valve and what lines you can also. Took me about 2 or 3 hours to replace the brake assembly probably 6 or 8 more the get the brake lights to work right.