Antilock sensors

[90Xjay]

I have had an intermittent "check antilock" light for several weeks now, it comes on when I barely touch the brake pedal and goes out in about 2-3 seconds usually whether I keep the pedal down or let off. Well now it has stayed on but sometimes still goes out on it's own and has also brought the main "brake" indicator light on occasionally.

I checked the fluid and bled the brakes, even though the pedal has always felt fine. I also just adjusted the rear brakes slightly, they were a little loose. I have not helped the problem at all.

I bought the jeep last fall, bone stock and did a 3" with 31" tires. Funny thing: I can lift up slightly on the emergency brake handle and the anti-lock light goes out and somtimes stays off until I hit the brakes again. I hope this is just a sensor or something I can adjust away. Any suggestions please??

 

[MudderChuck]

Just guessing, the only XJ I have with ABS, is the next generation from yours and has near stock tires (one size bigger). My alldata is for an 88, which probably isn´t the same as yours either.
I´d think maybe the ABS controller unit is tire specific or near tire specific (my Chev. is). Your XJ probably came with 27 or 28 inch tires.
The guys at www.naxja.com may have an answer, do a search at naxja. www.madxj.com is kind of a brake guru, his site may have some relevent information.
P.S. Checked out your site, like your ride, you do good work. I´m thinking of two toning mine an 88 8), think we have the same color XJ, mine is kind of a red/brown, cordavan or Russet (whatever they call it), silver accent looks good.

 

[90Xjay]

Thanks Mudder, :lol: glad you liked the Jeep page.
Today I took my jeep to a friend with a Snap On scanner and we kept having a commucation problem with the link, when it was working in between the comm error, it showed wheel speeds at different wheels at different times of 42mph?? This is with key on /engine off. I am suspecting bad ECM, and the pressure pump for the ABS runs constantly with the key on and I think it should go out when the sensor tells it the pressure is there. I have alot to check out and read up on that is for sure.

 

[MudderChuck]

Don´t know if it´s relavent or not, (different system) but the wifes 95, seemd to always (mostly/alot) have the pump working on her XJ, also chattered a lot, when stopping on osme road surfaces, really harsh. When I changed from, the 60 series tires it came with, to about 28--28 1/2" inch tire, the constant pump action, dissappeared, ABS function smoothed out some. One thing I did notice, is it didn´t stop instantly, when I changed the tires, it took some days. Maybe the computer and/or the brake controller needed to relearn for a certain number of cycles.
Pump valve body leak and excessive motor, in the early ABS units from Jeep. Seems like a pretty common problem, most people disable the ABS, have seen more than a few threads concerning this on other sites.
Might be worth a try to disconnect the battery, for awhile and see what happens. Simple and sometimes it helps, when things get a little wierd. But usually not a permanent fix.

 

[graewulf]

most likely a sensor is going bad and/or you have mud in there somewhere.. check the wheels.. there is usually a toothed gear behind the brakes that the sensor reads... anti-lock brakes don't care what tire size you have, so long as they are all the same size. the system is only concerned with differences in wheel speed. If you get mud in where the sensor is, or hit it with something/knock it loose you can get these kinds of problems. Check the connections too.. i know someone who had a connection come loose on his car and the antilock acted up.

 

[90Xjay]

Well, I tried to just disconnet the ABS by pulling the 2 amp fuse in the fuse box and the pressure pump stops working, the light stays on and the brakes become hard as heck. I can't hardly stop the thing on a panic stop.
If I put the fuse back in is stops good again. Very similar to unhooking the vacuum booster on an older car.
At this point I really just want to disable this thing, but I can't live with the hard brakes or the constant pump running. It could stop running under a hard brake and cause some problems on a hill somtime.
I think I am going to change out the ABS computer this weekend with a used on and then try and track down where the pressure is being lost, I think that is why the pump runs all the time.

 

[XJNick]

Hi,

I've always been under the impression that vehicles with ABS still have a vacuum operated brake booster. If thats the case, then you shouldn't be feeling a hard pedal simply due to the ABS being disconnected if the booseter is functioning properly. But then again I don't have ABS on either of my Jeeps :mrgreen:

But I guess you have no vacuum booster?

-Nick :!:

 

[graewulf]

there's still a vacuum booster with ABS, but when the system is offline it goes into a bypass mode, and some vehicles lose the front brakes when this happens... Get it fixed by someone who knows ABS.. you may not have a computer problem at all....

 

[90Xjay]

I have been checking this thing out more thanks to Mudder for the links and to all of you for the good info. When your ABS pressure pump begins to run alot, that indicates a loss in pessure. When your master cylinder begins to bypass, this allows the pressure to drop and makes your pump run when you use the brake. All of the test I have been doing point to master cylinder bypass. This ABS system is unique to just a few year models, but if the ABS pump is offline, you have very hard brakes, the ABS pump provides the brake boost you would normally get from a vacuum style booster.

 

[90Xjay]

After looking more at Mudder's links he suggested( Mudder you definatley have a Christmas card coming from me this year!!) I found out that my year model XJ had the Bendix 9 or 10 ABS system which if the pump and or actuator fails, the main hydraulic brake become near impossible to panic stop. While most all other ABS systems enhance your ride's brakes, this system depends upon the ABS pressure pump for the "boost" that a normal vacuum booster system would normally give. These systems do not incorporate a vaccum booster. Hence the NHTSB enforced a mandatory saftey recall on Chrysler in 1997 making these systems subject to a full warranty as long as the vehicle is running, mileage and age does not matter.
The Recall # is 96V260000.
My XJ is in the dealership right now waiting for a new pressure pump and actuator to be installed tommarrow --FOR FREE!!!!!!!! :lol:

 

[MudderChuck]

I read through the ABS threads at NAXJA last night and noticed there was an open ended recall on the early ABS (was gonna tip you off), doing a search on Bendix (at NAXJA) turns up a whole lot more info (nice to know, might be usefull next time). If you ever decide to do, the tear it out by the roots approach (recall is only good once, I believe), what Madxj did on his site, seems to be the best replacement setup, for about the same cost as the original stuff.
Glad it worked out for you.
My booster is hissing, gonna do Madxj´s dual diaphram steup this summer. XJ´s are never ending fun. Kinda glad I don´t have the ABS.
www.alldata.com is worth the subscription, even if you have the FSM. They list all recalls, and major customer complaints, there electrical section is fairly complete and broken down into sub sections.
Headache, a regular NAXJA forum poster, has a thread today, ABS revisited. Gives a little insite, into what happens when the master cylinder, goes from internal leak, to complete failure.

 

[90Xjay]

Re: Rubicon production ceased

Mudder, The local dealer who is doing my recall said, and also according to the printout I read, the warranty for the pressure pump and main actuator is forever. Their records show that this is the second time around for my XJ, but it don't matter, they gotta fix it.

 

[MudderChuck]

Good news, not everything you read on the net is fact. Might want to post your experiences at NAXJA, and help out some of the guys.

 

[jerryoster]

I have a GCherokee 1997 and the ABS light intermittantly comes on. The dealer said I need a new pump ($1000 !!!) The brakes otherwise seem to work fine in regular mode with no evidence of vacuum assist loss. Does anyone know what type of ABS was on the 1997 GC? I noted the Bendix recalls mentioned here. If I really do need a new pump, anyone know of a source for a less expensive pump, or a good pump from a junked vehicle. Also, what years's pumps might be compatable with my 1997?
Thanks