Rear Anti-lock brakes not working
 

Hello everyone,
I was wondering about my rear antilock brakes on my 94 pickup. I had purchased new brake pads and shoes at NWOR, and upon inspecting my brakes, I realized that they didn't need to be replaced yet. However with the wonderful "no refund" policies at NWOR, I was stuck with them so I just replaced them all. That was about 2 months ago now. I noticed that when I slam on the brakes that the rears no longer pulsate (the anti-lock function). When I took off the rear shoes, I didn't open the brake lines. I was wondering whether there is a fuse or something that will restore the function to my rear anti-locks. It stops fine and all, it is jut not working "properly." Any experience with this problem? :bang:

I don't have an answer, but I wanted to bump this because I'm having the same problem in my '95 V6...

rear anti-lock lights pops on during start-up then turns off which I think is the normal behavior. but I can't feel any pulsing the brakes when locked up on snow or ice. Checked what I think is the ABS fuse and it was okay...

Anyone?

Just wondering, but, how do you guys know it's not working? I've never been able to feel any pulsing in the brake pedal. Have you guys tried slamming on the brakes in a controlled situation and gotten out to see if there are skid marks?

:) Steve

Other ABS systems I've used (Honda/Acura) I can feel the pulsing quite strongly. Maybe this isn't universal.

Also, the car slides in slush under braking as if under full lock. It doesn't feel like it has any directional control, like the other ABS equipped cars I've driven, but those were full ABS, not rear-only.

Hey guys,
The reason that I know it isn't working is because I know that it used to work. I had made a few "panic stops" in my truck before and the brake pedal used to pulsate because of the rear antilocks. After changing out the pads/shoes and having the rotors turned on the vehicle, and the drums on a brake lathe, well it doesn't pulsate in a panic stop anymore.

Could it be possibly, the rotors and/or drums were warped, and you thought that pulsation was your ABS?

And when you did this, the problem was corrected.

You have any pictures of your engine bay? I dont remember ABS being an option on 94 Pickups.

Jay

They put abs on drum brakes?? Ive only known it to be on disk brakes... but, what do I know? Not saying you don't have abs on the fronts. Different ABS systems make different noises... but you should definately feel SOMEthing, espcially on ice. My 'ol volvo used to make a farting noise when I was on ice/packed snow. Amusing for about 3min... oh well, my 3rd gen makes an odd sound too, its more than just pulsing, though I feel that too.
ps, sorry... its late... hope something could be had from my latenight babbling :yawn: oh well, off to bed.

lol :laugh: that's too funny!




Yup, for the 2nd gens we only got abs on the rear drums.

Steve

Here's an easy way to test them that get's my ABS going everytime. Go out into a field or somewhere you can spin the tires in 2WD. Turn like your going to spin a cookie and spin the inside tire. Immediatly after this slam on the brakes you should get the vibration in the pedal. I've gotten it there several times when out wheeling. Good luck getting to the bottom of the problem.

I am pretty sure that my rotors/drums were all right, I just had them turned because well it should be done. AS far as the pulsation, it would do it on wet pavement, or on dry loose surfaces such as a gravel road... especially when turning. I bought the truck used in 99, and I have the "Rear Anti-lock" indicator when I first start up the truck. So what should I look for under the hood to determine once and for all whether or not I have anti-lock rears? :pat:

Look on the rear diff. Right on the top of the diff is the ABS sensor. It has a line that looks like a brake line that is mounted to the back of the fuel tank but is seperate from all the brake lines. If you have this little sensor you've got ABS.

I was under there yesterday changing the fluids in all the gearboxes, and there was an electrical connection on the top of of the diff. So do all of the trucks/4runners even the ones without rear anti-locks have the "rear anti-lock" light when you start up the vehicle?

I figure you got to have antilock brakes if you have the light. I'm fresh out of ideas but I can't image why changing the brake pads/shoes/drums would do anything to the antilock brakes.

Good luck,
Steve

Regarding the ABS not working onice/packed snow, I don't think it WILL work all the time on these surfaces. There system has to feel that there is some friction or resistance working against the tires in order for it to actuate, so with the very low amount of friction between ice/snow and tires I can see a lot of times where the sensors will not detect any resistance.

I would also concur with the possibility of the drums/rotors being a little uneven. Wouldn't take much for it to really be exaggerated under hard braking with ABS.

Also, ABS will not always kick in. This may be different for different manufacturers, but some won't kick in unless you really have the brake pedal buried. It also does not kick in every time you brake, since ABS actually increases your stopping distance. ABS was designed so that you could steer around the obstacle while still maintaining steering control, NOT so you can stop before hitting it. There is definately more friction under a tire that is locked up thanone that is rolling under ABS, which is why, in most cases, locking up your brakes results in shorter stopping distances than ABS.

I am no mecahnic, but I get to do a lot of high speed driving/training for work, and these are the things I have learned and experienced.

Finally, my '91 truck has ABS (drum) in the rear only. When it is NOT FUNCTIONAL, the ABS light comes on and stays on until the problem is fixed. I would expect this would be the same for you (???). Could it also be that, with the new pads that provide more efficient braking, not need to actuate back on forth so aggressively, resulting in you not feeling it kick in?

Honestly, I would think that if your ABS light is not on constantly, your system should be working. The light comes on when you start the car to indicate that the system is "charging".

Well I looked at the fusebox under the dash and there was a 15A ABS fuse that was intact. Don't know where to procedd from this point.

I guess your next step would jsut be to take it to the shop and have them test it. :dunno:

If you only have ABS in the rear, then it's gonna take a heavy foot on the brake pedal to get the rears to get to a point where the ABS will kick in. In my experience with both my 92 (w/ rear ABS) and my 2000 (w/ 4-wheel ABS), the 2000s kicks in alot more than my 92 (with the pulsating/grinding noise), because of the fact that the fronts also have ABS. Unfortunately, with my 92, my front brakes will lock before the rear ABS even comes close to engaging because there is a whole lot more braking power going to the front (70/30). The *only* time I feel the pulsating/grinding in the brake pedal is if I downshift and pop the clutch out, backfiring the rear wheels. Sometimes I will feel it offroad but not alot.