Hello everyone, this is my first posting.

 

 

My son has a 91 Legacy Wagon that has a strange ABS problem. Sometimes when the brake pedal is pressed, about once out of 25 or 50 times, the ABS pump activates. You can feel the ABS pulsing the brake pedal. I checked all of the wiring under the hood and at each wheel looking for breaks or any obvious physical problems and everything looks fine. The other strange thing is that the ABS light never comes on but does work during the self test cycle when you move the ignition key to the first position the ABS light will iluminate. I am a long time backyard mechanic but have never had a car with an ABS problem and have no good documentation on the ABS system for this car. So any help or ideas would be appreciated.

 

Thanks

is he braking hard enough to lock the wheels?

The wheel may be locking or the sensor thinks it's locking.

Clean the tone ring and the gap between the ring and sensor. Mine rings developed a lot of rust and there was magnetic fuzz in the gaps. Chech the gap for the correct spacing.

Check under the passenger seat to see if any codes are flashing (open up the little carpet flap).Good luck.

alldata.com mentions "ABS - Relay sticking", circa 1996, but nothing elaborated about that. Doesn't say if the light will be on or off. It's in the service bulletins list generated for the 1991 Legacy Wagon but also shows up for other MY's.

 

If you don't know anything about ABS stuff, like me, then not sure that will help much.

Thanks for the input from you kind folks!

One thing I forgot to mention is that this problem happens while the car is idleing at a dead stop.

One thing I did find was a fair ammount of metalic fileings around the rear wheel sensors, on the back of the wheel, which I blew off with compressed air. Could crap around the sensor on the inside cause something like this? At one point the brake pads wore down to the metal and had metal against metal for a while so there could be metal fileings arount the sensor area on the inside of the wheel...I'll have to look at that this weekend.

It's the metal shavings.

 

 

While you have the wheels off, check the flexible rubber hoses that run to the calipers for "ballooning". Tends to throw off the ABS too.