'91 Explorer rear anti-lock brakes not working!

[TedfromVA]

My anti-lock brake light came on and they are not working!! It goes of sometimes then come back on. It's snowing here now and its been real fun sliding around but not exactly safe. Can anyone help?
Also I have an automatic transmission with 4 wheel drive in it now. Its almost shot, I lost overdrive about three days ago. Its just a matter of time before im setting along the road. Since I have had it rebuilt once I want to convert it to a five speed. Can you recomend the correct doner vehicle(s) to get one from? Any info will be helpful. Explorers Rule!

 

[ld50]

first of all, the anti-lock is only on the front brakes.

Check your hubs to ensure they are tight, that can light the ABS up. When mine did that it would clear when I restarted it, then come on when I did a sharp turn.
Tightened the hubs because one side was just a little loose and it fixed it.

Other than that, maybe the snow has something to do with it?

The best donor vehicle would be another explorer

or you could get the parts together and get some info from a thread around here by someone who has done it.

Use the search feature in some different parts of the forum and I`ll be you get all the swap info.

-cheers and welcome

 

[Opera House]

RABS is rear antilock brake system

on this vehicle. Never got a light on my 92 but don't ever think it worked. Have heard more people curse this system that most didn't think improved safety. If you havent been flushing this system on a regular basis you are in deep do do. Rear brakes should still function with this failure. I know one person who tried to blead the rear brakes and couldn't get any fluid out. Had to replace a clogged brake line. You haven't done any brake work recently. Improper bleed procedure can lock up the RABS unit. Have you checked fluid levels?

 

[ld50]

I thought anti-lock was only the front on 1st gens?

I`m confused, mine and a couple I`ve seen only have front ABS, did they really make first gens with something else?

Could be wrong, but I thought abs was a disc brake thing.

 

[ld50]

I searched and found that people say 92`s had rear abs.

I have a 93, and No rear ABS. Why is that?

I found a thread that says 91 and 92 were rear only, but I thought my buddy`s Ex (91)had front only like mine.

guess we need to know what he has for sure.
Is it an ABS light, or a RABS light?

 

[Opera House]

That seems reasonable ABS and disks

but my book shows the RABS valve interupting the brake line to the rear wheels. I have never felt mine work in all the years I owned the vehicle. Valve is easy to get at if you remove the transmission. Who thought that up?

Do have one suggestion for this fellow. Remove the speed sensor from the rear differential and clean it. These have a strong magnet that picks up metal particles. This reduces sensor output and could cause a light. My 97 was really coated. It is a shot in the dark that I don't think will help if he gets the light durring self test.

 

[JDraper]

As far as I know, no Explorers came with front ABS only (which would be inherently dangerous). They either came with Rear ABS (RABS) or 4 wheel ABS. I checked both my CD and repair manual, and neither mentioned anything about a front ABS only system. My old '92 had RABS, and I believe that RABS was only available in 91 and 92. Both the book and the CD show that RABS was 91 and 92, with 93 and later having 4 wheel ABS. I also looked in the manual for my old '92, and it only mentions the RABS system.

As for your problem, there are several possible things that could cause the problem.


1. Your ABS sensor could be bad or dirty. It's bolted into the rear axle housing. Fix is to remove the sensor and clean it, or replace it if bad.

2. The RABS module could be bad. It's located inside the driver's side frame rail where it starts to arch up to clear the front axle. Fix for this is to replace the valve, which is kind of expensive.

3. Your brake fluid could have too much water in it. Brake fluid is hydroscopic, meaning it absorbs water. When the fluid absorbs too much water, the specific gravity of the fluid goes down and fools the pressure sensor into thinking there is not enough pressure. This turns on the RABS light and disconnects the RABS system. (This is what happened to my '92. The cure is to get the brake system purged and replace the fluid. Sometimes it takes a couple of days for the light to go out afterwards because the RABS valve is on a dead end, and a little of the old fluid will remain.

4. Low fluid, but this is usually accompanied by the red brake light being on too.


Good luck and welcome to the board!

 

[ld50]

but my book shows the RABS valve interupting the brake line to the rear wheels. I have never felt mine work in all the years I owned the vehicle.

LOL, me neither, but I sure can feel the front sometimes. I even swear the rear have locked up a couple times on me.

Anyway Jdraper thanks for the info, I`ll look into it, I found another thread here that says the sensor for the rear is at the rear axle(?) or somewhere other than the wheels. I think you`re right, it does seem dangerous to only have front abs.

 

[TedfromVA]

I have a few places to start now!!!

Thanks for the responses! I will let you know the what works to fix the problem.

 

[TedfromVA]

P.S.

It s a rear ABS also.

 

[old mechanic]

My book says that my 92 has rear ABS only and that the rear ABS does NOT work in 4WD! And I found out that their right! My rear end swings out when I apply the brakes in the snow in 4 WD! Seems OK in 2WD!

 

[JDraper]

Yep, the rear ABS does not work in 4WD. If it did, we probably still would have my '92. When my wife had the accident, the rear end came around in 4WD and put her in the ditch that rolled her over. If the RABS had been functional in 4WD she probably could have controlled the slide. Only problem is that in a true 4WD system (i.e. no clutches in the xfer case) it is basically impossible to have ABS because all components of the drivetrain are tied together. With the clutch controlled xfer cases in the newer explorers, the ABS can decouple the drivetrain momentarily to make it work.

 

[ld50]

So would my 93 then only shut off the rear ABS when in 4x4?
Or is it all shutoff?

 

[old mechanic]

In 93 the X added (4 wheel) anti lock brakes that work in 2WD AND 4WD!!!

 

[ld50]

Hehe, kind of a trick question, I know my antilock works while in 4x4, as a matter of fact it is bothersome.
And I swear the back tires lock up while the front will do that abs chatter...

hmmm

 

[AlaskanJack]

Well I went through and replaced everything on my 91's brake system only to discover that my rubber line in the rear was swelling under aplying brakes.

So if you need a RABS valve or anything else give a yell I have removed the RABS from my system.

 

[FirstFord]

mine werent working for a while, changed the abs realay under the hood now its fine.

 

[TedfromVA]

Update!

Checked the sensor in the rear. Cleaned it! Still no change. The light is still on. Did not have anyone to help bleed the brakes, but i did find the control unit on the frame rail. YIKES!!!! Hope i don't have to replace it. Not eaxy to get too! I might check that relay next.....

 

[TedfromVA]

UPDATE

I had time to bleed the brakes the other day an it did not fix them, i guess, i will have to replace the RABS unit to get them to work.

 

[Padiano]

Sorry to revive an old post. But what ended up resolving this?