Did search: Bendix ABS revisited

I have a '91 XJ with the Bendix-9 ABS system and yes I know that I should get it replaced. I just have to find a good mechanic who is able to do it.

I had no problems with it, but a few days ago the brakes started acting strangely just before tha car comes to a stop. Brake pressure is then shortly decreased by the system and put back on almost immediately. It does not really affect my control over the car, but is not a nice feeling.

In order to disable the ABS system, I removed the ABS modulator relay: that means I have no ABS, but the problem is gone.

Is there any danger in the removal of the ABS modulator relay? The only difference I note is that the amber 'check antilight' is on permanently, but I can live with that.

Thanks in advance,
André

Headache said:

I have a '91 XJ with the Bendix-9 ABS system and yes I know that I should get it replaced. I just have to find a good mechanic who is able to do it.

I had no problems with it, but a few days ago the brakes started acting strangely just before tha car comes to a stop. Brake pressure is then shortly decreased by the system and put back on almost immediately. It does not really affect my control over the car, but is not a nice feeling.

In order to disable the ABS system, I removed the ABS modulator relay: that means I have no ABS, but the problem is gone.

Is there any danger in the removal of the ABS modulator relay? The only difference I note is that the amber 'check antilight' is on permanently, but I can live with that.

Thanks in advance,
André

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Headache the fluctuating pressure when stopping that your describing is what happens when the master cylinder seals start going bad. That is exactly what mine (’91 limited with POS Bendix ABS) did for about a week before the master cylinder actually went. There is no warning when it goes, mine when from the fluctuating brakes to no brakes in under 30 feet. When the mast cylinder goes you will have NO brakes. I found this out the hard way when I came out of a Wal-Mart parking lot and inadvertently merged with 4 lanes of traffic. I just about broke the center console trying to get the emergency brake on. After I limped the Jeep home on emergency brakes I promptly clean the seat and changed my pants After a few phone calls I discovered that the Bendix ABS is covered under a recall, but the master cylinder is considered a normal wear item. You may or may not be able to get your local dealership to replace it. If you have to replace it yourself it runs about $240 from Shucks. For the same price, or slightly less if you are frugal, you can swap it out for a conventional system. That’s the route I decided to go. It is a very easy project, nothing more than a remove and replace type of thing that I did in an afternoon. I would certainly not pay someone very much to do it. Go to a junkyard and find a ’95 or ’96 non-ABS Cherokee and take the vacuum boost, master cylinder and proportioning valve (they are all together on the same bracket). The hardest part is removing the old Bendix ABS parts and lines. Replace your old booster and master cylinder with the new one (the op rod is the same length and style as the old one and will fit perfectly). You will have to bend the brake lines a little bit to make them match up with the new cylinder, very easy to do I just bent them with my hands. You will have to cut the lines and put new fittings on them. This is also very easy to do, but you need a brake flaring tool (~$20) and a small cutter (~$5). I cut and flared the brake lines BEFORE putting in the new assembly. It gives you a lot more room to work with. Your engine should already have a tap in the side of the intake manifold for the power booster. Just hook up the vacuum line from the intake manifold to the vacuum booster. A little bit of Dawn dishwashing liquid makes the hose slide on much easier. Hook up the brake lines to the proportioning valve, bleed the brakes and give it a spin. I had to bleed the brakes multiple times to get all of the air out of the system. The difference in braking power is night and day. The first time I hit the brakes I just about threw myself through the windshield :laugh: Its pretty easy to lock up my 31”x10.5”s, I imagine this brake setup would be good up to 35” or so. PS Running with the ABS warning light on doesn’t hurt anything, you just don’t have ABS. If you want to turn off the light, open the fuse box under the hood and pull the relay labeled “ABS yellow light”.

Hi Wiley Coyote,

D'''''d if it is indeed the MC. It was replaced under warranty less than 4 weeks ago by an official dealer. Because I had problems with the ABS pump/motor assembly (sometimes it would not activate, leaving me without power assist), they re-did the 702 recall and replaced both the pump and the MC.

The ABS-pump looks brandnew, but the MC looks re-manufactured/revised.

But is it possible that the effect of the leaky seals disappears when I disable the ABS?

Thanks,
(Even more) Headache

PS: if it does not matter if the ABS system is disabled by removing the ABS modulator relay, I would prefer this to removing the fuse. In the latter case, the red warning light does not function anymore (I have just tested it) and that really is an essential warning in case system pressure drops to an unsafe level.

Sorry, I misunderstood your post. I thought you were trying to get rid of the stupid yellow ABS light on the dash, not the modulator. I don’t think that you can disable the pump modulator because that is what supplies your “power boost”. I can’t confirm or deny that because I un-installed my ABS. If you decide to disable the modulator, go to a nice quite empty parking lot to try it out and be prepared to use the emergency brake if necessary. I’d hate for you to run into anything or anybody. I’m pretty sure that they quit making those master cylinders (they are not the same as non-ABS master cylinders) so it would make since that they put a remanufactured unit back in yours. I’m surprised that they changed it for you. You must have done some sweet talking or have a really good Jeep dealer. That’s the only draw back to doing the conversion; as soon as you cut the brake lines you void the recall/lifetime warrantee. In exchange you get a better performing and much safer (for you and anyone in front of you) brake system. I stood and looked at my ABS for quite a while before I finally worked up the nerve to yank it all out. Looking back, I’d do it again in a heartbeat. PS If the master cylinder seals are going it won’t matter if the ABS is disabled or not you will still have that same mushy fluctuating feeling. Mine was also pushing brake fluid out of the top of the reservoir. If you are having problems locating a ‘95/’96 booster, Schucks (www.partsamerica.com) can order one for $100 plus $30 core charge. I have no idea how much shipping would be to the Netherlands, but it does have a lifetime warrantee. I just picked up a new one from them today, my old one was leaking

Its pretty easy to swap to a normal brake system. I did it for $70 in junkyard parts. All you need is a M/C, Booster, proportioning valve and a few brake line connectors. I just spliced the new setup into the existing lines. Worked great, the hardest part was tearing out all the ABS crap.

You could at the same time upgrade to a dual booster system off a 96+ if you want, but you'll need to also grab the brake pedal and bracket off the donor vehicle.

Wiley Coyote said:

"I don’t think that you can disable the pump modulator because that is what supplies your “power boost”. I can’t confirm or deny that because I un-installed my ABS."

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Even though the brakes worked o.k. after disabling the modulator, your remark made me think again. What I've done now, is disconnect one of the front wheel sensors. This causes the ABS to go directly into 'fault mode' after above a certain speed (a few mph), but probably this is safer than disabling the modulator. At least now I know what is happening.

I think I will replace the system anyhow by a vacuum boosted system. Even if it was for the least annoyance, namely the wwweeeeeeeerrrrrrrrrrtttttttt of the ABS pump after each three or four times of braking.

hey mine does like the same thing iv got a 93xj though how do u get rid of it?

Jeepster4wd said:

hey mine does like the same thing iv got a 93xj though how do u get rid of it?

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Get rid of what? If you mean the sound of the pump: in my '91 the only way would be to replace the whole bendix system with a conventional vacuum boosted system. In the Bendix 9 and 10 systems, the ABS pump also provides the pressure for the power assist, so you CANNOT (!) disable the pump. However, I do not know what kind of system was used on 93 models: the situation may be competely different.

Brake pressure is then shortly decreased by the system and put back on almost immediately. It does not really affect my control over the car, but is not a nice feeling.

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thats what i have I mean.... right as im about to come to a stop.

Jeepster4wd said:

thats what i have I mean.... right as im about to come to a stop.

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I disabled the ABS by disconnecting one wheel speed sensor.

I was already dissatisfied with the ABS as it made the car pull to the right when braking, probably due to a misaligned/broken wheel sensor or corroded ABS rings (or both). So then I got the problem with the decrease of the brake pressure just before coming to a stop: I do not know what the cause is, so decided to disable the ABS altogether.

oh so diabling ABS should get rid of problem? im pretty sure thiers a fuse or something i can pull which will stop the abs ?

Jeepster4wd said:

oh so diabling ABS should get rid of problem? im pretty sure thiers a fuse or something i can pull which will stop the abs ?

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I assume that there is a fuse, probably in the fuse box under the steering wheel. Be careful with what you do: the type of ABS that you have may be completely different from mine and disabling it might affect the brake function.

I decided to disable the Bendix-9 system on my 91 XJ by disconnecting one wheel sensor, as I know that the ABS should then fall back into 'normal' braking operation. In my case, the problem with the short reduction in brake power disappeared.

You may also search on this forum, as I have seen several threads where some people said that they pull the fuse to disable the ABS when they go wheeling.

I have a '92 XJ I6 with ABS. My ABS was doing wierd things (there is another post about this) so I just unplugged both electrical connections to the pump unit (located adjacent to the MC). I may not have the same ABS system as your '91. Anyway my "check ABS" trouble light is permanently on but the brakes seem normal. I've been driving it this way since January without incident.