NO (rear) BRAKES!!!

[Remus Redbone]

'95 Cherokee XJ SE with ABS that hasn't worked in years. Light is on. This rig had only 9000 mile put on it in the past 14 years, so obviously, it sat a lot.

The left front caliper was not releasing, so replaced the caliper and put new pads on both sides of the front Bled the side that got the new caliper. Brakes seemed pretty good.

Had a little too much pedal travel, (firm, but low) so decided to check some things. Jacked up the vehicle, started it, put in gear, and the wheels turned slowly. I hit the brakes and THE REAR WHEELS KEPT TURNING. Decided to a
adjust up rear brakes. Drivers side turned too easy, auto adjuster wasn't against the adjuster wheel, so I pulled the drum to inspect. Front shoe was worn out, rear shoe was still thick.

I very lightly pushed the brake pedal with the drum off and noticed only the front shoe moved, so new shoes and new wheel cylinder. When I got ready to bleed the driver side, I had very low fluid pressure. Wife was doing the pedal work so I thought she wasn't pushing very hard. Got the air out and put the wheel back on. Still hadn't touched the passenger side other than adjusting.

Since both rear wheels were up, I started it up and put it in gear. Wheels got up to about 5 mph, I pushed the brake and the rear wheels kept turning again. I stood on the brake and got them to stop, but unless I kept HEAVY pressure on the pedal, the wheels started turning again. Had wife assist again and told her to really stand on the pedal. I open the bleeder and get a very weak stream, just barely more than a dribble.

So, Is it;

1. Proportioning valve?
2. Improperly bled ABS system?
3. Master cylinder?
4. ????

No bends or kinks I can see in the rear brake line from the front to the rear.

[bruggz351]

Ok.
We just had a member on our Aussie forum with this exact same problem. His gremlin turned out to be mal-adjusted tone ring pick-ups, on the rear wheels. The gap was TOO BIG.
This tricks the braking system into thinking the rears are locking and reduces fluid pressure. The HCU is simply doing its job. But with incorrect information.

My advice is check the gap on the tone rings/pick ups on the rear wheels, adjust, and go from there.

HTH...

cheers

[Remus Redbone]

I don't know if the ABS can limit fluid flow to the rear since the ABS hasn't been functional since about 2000. I know for sure the pump is not operating. Is there some part of the ABS system that continues to function when the system is in fault that can restrict fluid flow?

[4.3LXJ]

Just for giggles pull the fuse for the ABS and then check the rear brakes

[Remus Redbone]

Did try pulling the ABS fuse and testing before the testing below. No change.

Testing;

1. Opened line to rear brakes at end of steel line just before "T" block on rear axle housing. Attached rubber hose and ran it into a jar of brake fluid; started XJ and operated pedal. Had significant pedal resistance.

2. Opened rear line where it comes out of ABS pump. Attached rubber hose into jar of brake fluid. Still had significant pedal resistance.

3. Opened rear line coming out of proportioning valve where it enters ABS pump. Attached rubber hose int jar of fluid. Freed fluid flow & almost no pedal resistance.

Conclusion: ABS pump restricting flow to rear brakes. Bruggz351 says above that a member on the Aussie forum found the pickups too far from the tone ring on rear and the ABS was just doing its thing. That sounds like a problem diagnosed on an ABS system that has been working. The ABS on my rig hasn't worked since some time around 2001. I'm going to plumb around the ABS pump for the rear feed & move on....

[4.3LXJ]

That is what most people do. It is an expensive fix

[Remus Redbone]

Well, the plumbing to bypass the ABS pump isn't obtained by just moving the connection from the pump to the proportioning valve. The fittings on the pump are metric and have a bulb flare, whereas the proportioning valve ports are English with a common flare. As the guy at NAPA said, "Chrysler did everything they could to keep you from bypassing the pump".

I got the guy at the salvage yard to make me a bypass line for the rear brakes, but little did I know the output of the pump to front and rear are common, so you can't just bypass the rear unless you plug the rear pump ports or you're spraying fluid on every brake pedal press.

I put everything back original, the ran a wire from the battery and operated the pump a few times, then I did a four-wheel brake bleed. I'm back to a full pedal with what feels like good brakes.

Now I'm going to see if I can fix the ABS problem. Can anyone tell me where the ABS control module is mounted on a '95 XJ?