My 95 Bronco has a weird problem I can't figure out. After running for a while my ABS light comes on and I feel relieved! After the light is on, I know my brakes will work until the next time I turn off the engine.

Before the ABS light comes on, it is a total crap shoot. Sometimes it'll work, sometimes the pedal goes to the floor and I feel it clicking. I quickly pump the brakes and usually it will catch and work, other times it will lock up on me.
Once the ABS light comes on, it runs fine - I could drive it all day with no problems.
Any Ideas / similar problems ??

 

Sounds like the on board ABS computer is having problems or going out, (but I'm not completely sure since mine doesn't have ABS.)

But are you saying that before the ABS light comes on, the brakes sometimes don't work at all? If so, first and foremost, I would not dare move that vehicle again until that problem is fixed. That's the kind of brake issue that could get you and someone else killed quickly.


Found this article, may point you to some more information:

https://www.ford-trucks.com/article/...ff_Switch.html

 

The rear ABS has a modulator/accumulator assembly that either adds back or bleeds off pressure to the rear brakes depending upon what the ABS sensor on the differential ring gear tells it the ABS computer. If the ring gear starts to decelerate too quickly (rear tires about to lock up) the modulator/accumulator bleeds off some pressure. Then it starts to add back pressure until the sensor says the ring gear is decelerating too quickly again (tires about to lock up) then it bleeds off some pressure and then starts adding it back again. This all happens multiple times per second and creates a balance where the rear tires receive near maximal brake pressure but do not actually lock up.

Sounds like the system is getting confused and it is thinking the ring gear is decelerating too quickly when it isn't. Thus it bleeds, and bleeds, and continues to bleed off pressure sometimes, and you end up with no rear brakes. Other times the system thinks it needs to add back pressure when it doesn't. So it adds, and adds, and adds more pressure and the rear tires lock up.

At some point the ABS computer senses something is amiss and so it disables the entire ABS system. The modulator/accumulator will no longer change rear brake line pressure. It's like it not even there. And you default to a 4-wheel non-abs braking system.

You can force this to happen if you just get under your bronco and pull out the electrical plug at the top of the rear differential. Then 2 or 3 seconds after you turn the key the computer will realize something is amiss and disable your ABS system. If the rest of your braking system is operating correctly this is not too big of a problem, them brakes will still work fine. But now they will lock up during a hard braking maneuver. Especially on a wet or slippery road.

You might disable the ABS like this as a temporary measure and then fix the ABS later, or just disable it permanently and drive very carefully on slippery roads. It sounds like you most likely have a bad ABS sensor. A bad modulator/accumulator, deteriorated wiring, or needing a new magnetic ring for the ring gear are other less likely possibilities.

 

His 95 has 4-wheel ABS so there are more potential failure points than the VSS in the top of the rear differential. There are individual excitor rings on each front wheel as well. Once the ABS light comes on, the computer is out of the equation which is why you can rely on the braking system again. The ABS portion of the system is no longer part of the process. I have my own opinions about ABS so I won't comment further except to say that the ABS computer generates its own set of fault codes and can be diagnosed just like the EEC-IV engine management system can.

 

Thx - The idea of disabling the ABS sounds like the only solution I could afford to try at this time ! As 91Bronc300 suggested, I will pull out the electrical plug at the top of the rear differential tomorrow and test it out (before mixing in with traffic). greystreak92 is correct that mine has the 4-wheel ABS. With that plug pulled, maybe the computer will quickly sense there is a problem and kick the ABS off? Will let you know what happens......

 

Abandonedbronco - Thx, I printed that article. It appears to be tailored to cutting out the 4-wheel ABS like I have. I'm going to try a shortcut suggested by 91bronc300 first to see what happens

 

Losing one sensor will trigger a fault but not necessarily shut the system down... the simplest way to disable the silly thing is to pull the fuse. You will have to either pull the "ABS" indicator lamp in the instrument cluster or just live with it being on all the time. That's the way mine has been disabled for years.

 

Honestly, you or your Bronco won't die without it. I've had a pickup without it and aside from two my not paying attention *** situations never had problems. They wiegh just over 6k lbs anyway, they stop past the dime regardless.

 

If the brakes act like normal every day brakes when disconnected, no, it'll be fine. May not stop as well under certain circumstances, but it's a whole lot better than not stopping at all. A lot of Broncos don't even have ABS to begin with, and didn't for a long time.

 

Oh, whoops. I didn't know late model broncos had 4wheel ABS. I run a 91 and I guess I just figured they didn't update them much before they (foolishly) killed them of in 96.

I hope it's a simple fix.

 

The ABS system becomes completely passive once it loses electrical power.

 

Well guys, Thanks for all the help. I pulled the fuses for the ABS a couple of days ago and problem solved. The ABS is disabled and I can drive with confidence. Really a super simple solution. Living in desert, so I will probably never miss the ABS. Thanks to everyone - Ken