Brake Problems ABS System

My brother has an 89 XJ with ABS. The brake pedal is rock hard, like no vaccum boost. It dosen't have the standard booster behind the master clinder, but a ball to the left of the master (looking from in front of the engine compartment). I don't hear any leaks, do these systems have common issues that I should be looking for?

StuckonTheDock said:

My brother has an 89 XJ with ABS. The brake pedal is rock hard, like no vaccum boost. It dosen't have the standard booster behind the master clinder, but a ball to the left of the master (looking from in front of the engine compartment). I don't hear any leaks, do these systems have common issues that I should be looking for?

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The Bendix system is crap! OK I got that out of my system....

The Bendix system does not have vacuum boost. It relies totally on the pump located on the passenger side firewall for braking pressure. It should cycle every so many brake uses (a small buzzing sound). The "ball" you talk about is the accumulator. It is a dangerous little sucker if you don't treat it right. Its job is to store the pressure on the brake fluid until needed by the modulator (the big block where the master cylinder should be). Before doing anything with the brake system, pump the pedal with the power of at least 40 times to bleed off any residual pressure "stored" in the accumulator. Even then the accumulator still holds a nitrogen charge and should be treated with care.

There was a recall on the Bendix system because of a failure in the accumulator that cause excess cycling of the pump and its subsequent failure. Without the pump you had no brakes. It's the same if you blow a pump fuse, you will loose your brakes. Loss of power of any sort and you loose your brakes. It’s the stuff of law suits. Actually if you remember the law suits against Chrysler over the minivan ABS failures of the late 80’s early 90’s, it’s the same brake system.

Make sure you hear the pump run if you press the pedal down several times. Beyond that I would take it to a dealer to have it checked out if you aren’t very mechanically inclined. If you decide to tackle the project I would recommend a Factory Service manual as most Chilton type manuals won’t cover this system well, probably because of liability issues.

My suggestion is to pull the Bendix system and install a non-ABS set up out of a ’96 XJ. You loose the death trap of a Bendix ABS system and gain the dual diaphragm brake power of the later XJ’s for a huge improvement in braking power.

Bendix survivor,

Bones :skull1:

Thanks Bones, I think your post says it all, it is time to swap out the system!

StuckonTheDock said:

Thanks Bones, I think your post says it all, it is time to swap out the system!

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Now check out this old post...

Here

Bones :skull1:

Man! That is gonna be a pita, will the system out of an '87 work in a '90? The joy is going to result from the fact that the '87s owner used it as a salt water boat launch vehicle, and never was much on rinsing things off after. Will have to lube all fittings for a week to get them to break! What size are the line fittings, I have no line wrenches, so will need to buy the right ones...

StuckonTheDock said:

Man! That is gonna be a pita, will the system out of an '87 work in a '90? The joy is going to result from the fact that the '87s owner used it as a salt water boat launch vehicle, and never was much on rinsing things off after. Will have to lube all fittings for a week to get them to break! What size are the line fittings, I have no line wrenches, so will need to buy the right ones...

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I'd grab the hard lines and all (including the pedal assembly!) from a salvage donor vehicle. Most yards won't sell the used lines as replacements for legal reasons. I just told them I was going to use the lines as templates for new ones. I got them for nothing when I picked up the rest of the non-ABS stuff. If you are worried about getting things apart just replace the rear brakes including the wheel cyls, all flex lines, and calipers with new stuff. The only line I kept from the ABS system was the right front line. All the rest were replaced when I went from the ABS to the '91 non-ABS. If you do decide on new wheel cyls in the rear check the cyl diameter between the ABS and non-ABS cyls and use the largest diameter ones. I went to a D44 at the same time so I never looked into the sizes for the D35.

I recommended the '96 stuff because the dual diaphragm booster adds a lot of braking power over the single diaphragm of the pre 96 XJ's. I did it in two steps as I was the guinea pig on the swap. At the time I did it the only advice I got from DC was it couldn't be done, and from one other source, "just cut it out and replace it." Not much was available and I was forfeiting my warranty from the factory so I was a bit cautious at first.

It's one of the best safety mods one can do to the pre '92 ABS systems these days. I still can't understand why DC hasn't offered this as an option to repairing the overpriced Bendix crap.

Bones :skull1:

I have the donor vehicle on hand, and it is the one that I am worrying about getting the parts off of, you see, the fellow who owned it before giving it to me used it to launch boats in salt water, and wasn't real worried about rinsing it off, cause it's other job was as a tractor, dragging logs out of the woods, pulling Scotch Broom (bane of the Pacific Northwest), etc. So I really worry about the chances of getting brake parts off intact....