Anyone have any tips on diagnosing inoperable rear brakes (ABS)? I can tell they arent functioning by the way the truck drives. Shoes are brand new. Lights on dash (rear abs, brake) are on constantly. I have bits and peices of a toyota shop manual (on cd) and as far as i can tell, the problem stems from a speed sensor on the rear end. Anyone tinker with this sensor? I imagine it reads the edge of the ring gear to compensate for rear wheel lock up. If this is something other than a simple sensor replacement, im just going to remove this abs stuff, and install a porportioning valve to level out front / rear pressure.
This sensor wouldnt have anything to do with the cruise control would it? (inoperable also) Any tips or shared experience would be greatly appriciated.

91 4run SR5, V6

Brian
Sarasota, Fl.

 

I don't know much about the ABS, but if you rear brakes aren't working that is more likely improperly adjusted shoes. There is a small rubber plug in the inside of the backing plate, remove it and you can reach the adjusters. Lift the back wheels off the ground and adjust until the shoes just start to scrape, then back off a couple of clicks.

The rear brakes are self adjusting and should move the adjusters when breaking in reverse. Of course the adjusters could be rusted up in which case you'll have to take the drums off and clean or replace them. If you do that take one adjuster off at a time so you don't mix them up. It's easy to do,(and no I'm not telling you how I know that ).

I have the entire section from the service manual if you want to pm me with and email address I'll send it to you. It has everyting on testing the ABS.

One other thought if the brake warning light is on all the time you could have air in the rear lines. You might want to try bleeding the brakes in this order, FR, RR, RF, LF and then bleed the proportioning valve above the rear axle. This last one is important to get all the air out.

If you're driving with only front brakes you'll overheat and warp the rotors so hopefully you get the problem solved.

 

Non functioning ABS will not affect your braking or the way the truck drives (except if you brake hard enough to lock up the rear wheels, they will lock up rather than pulse.) The most common problem is the sensor in the rear housing not being close enough to the ring gear. Most are adjustable but I can't see how these would be. My light is on too. Other than looking at the sensor when I put my gears in, I haven't tried to troubleshoot it yet, so I'd be curious to see if anyone has a solution.

 

The sensor can be checked with a multimeter by reading the resistance etc. A chiltons or the CD should tell you how to do this.

A lot of times when the Pbrake light comes on it means the fluid is low, try filling it to the full mark.

The malfunctioning cruise control should give you some trouble codes. Again, a chiltons or the CD should tell you how to diagnose is.

Your 4runner already has a proportioning valve.