My brothers truck, a 1993 F250 4x4 5 speed 460 c.i., has the abs light staying on. The light has been on since he has owned it, about a month. He noticed that once in a while during a regular stop, the brake pedal will feel hard, the abs light will go out, and the brakes will not work as good. Then at the next stop the brakes are ok and the light is back on. Any ideas on what is causing the problems? BTW, the front pads are thin, so we are replacing them tonight.

 

Brake light is activated by; the emergency brake applied, Fluid level low in master cylinder (Float switch). Check wiring to be sure nothing is grounded. Also the float switch in master cylinder may be stuck or hte emergency brake switch may be stuck or broken.

 

The light I'm talking about is the yellow "abs" light, not the red "brake" light.

 

The ABS light will come on if brake fluid is low. That's a fairly normal issue. Brake fluid levels drop as pads/shoes wear out. It is normal to have to top off the brake fluid once in a while throughout the life of a set of pads and shoes.

Another thing. Brake fluid should be bled once a year, to get rid of contaminents. Brake fluid, by nature, absorbs water. Living in Vancouver, you're especially susceptable to water in the fluid issues due to the amount of humidity in the air all year round. Consider even bleeding them every 6 months just to be sure...brake fluid's a lot cheaper than new brake parts. Start at the right rear wheel, then left, then front right, then left.(Working from furthest to closest wheels from the master cylinder)

I'd bet the front pads being thin is part of the problem. The reason the light will go out once in a while, say several stops in quick succession, like city driving during rush hour, is that the brakes are pumped up, but once you get a block or two in of steady driving, they are back to normal. This would indicate a low fluid problem, likely caused by the worn front pads.