emlmarck

1992 D250 5.9L Cummins; Automatic transmission; 230,000 mi

Hello all,

My brakes seem to work fine (soft for 1/4 of the way down and hard for the remaining 3/4) despite the fact that my brake and antilock warning lights are intermittently on at the same time and sometimes stay on.

Recently only the antilock warning light was showing which made me nervous. I noticed that when I shut off the truck I hear a hissing sound from the back of the power booster (where it meets the dash). I dont hear it when the truck is running.

I have read various posts about people replacing their power boosters. Just wondering if that hissing noise is normal or an indication of a specific problem.

Thanks!

j_martin

Not normal. The booster has reached the end of it's life.

The light on is probably from the low vacuum switch. It'll light both lights.

thrashingcows

The seal around the outer surface of the booster piston is shot. Time for a new booster.

emlmarck

Thanks guys.

I appreciate your fast responses.

Is this something that could make my brakes fail completely? In other words should I stay off the road until it is fixed?

Thanks.

j_martin

Brakes won't fail. If the booster fails you'll have to put both feet on the brake pedal and attempt to pull the steering wheel, but it'll stop.