Strange brake performance

[Guest DTerry]

Got a call from my son this afternoon, said he had no brakes and the brake light was on. Told him to stay put and I'd come get him. When I arrived, he told me the brakes were working again. I turned on the ignition and waited until the pump stopped (seemed like an awfully long time), light out; turned off ignition and it took 6 strokes of the pedal to exhaust the pressure and the pedal to become hard. Ignition on again and it took about 30 seconds for the pump to stop, light off. Well, it's dinner time, so we took a dinner break, and in about an hour came back to the car. Everything checked normal, so I drove it 17 miles home, no problem. Re-checked pump down strokes and pressurize time, and it's perfectly normal.

What the heck? Anybody have any idea what could have happened? Other than electrical - and the pump was running - how could it be intermittent? The accumulator can't be intermittently bad. Stuck relay? But they're solid state. I'm baffled.

[Guest F14CRAZY]

I'm thinking that your relay is defective. I can't remember which of the three it is near the firewall at the moment, but I think the harnesses have stickers on them which will indicate which is the ABS relay.

It could also be your pump motor failing. If possible, when the pump dies again, see if there is power going to it with a voltmeter or test light. if there is power, it's the motor. No power would be a bad relay. I wouldn't think that the pressure switch would be intermittent.

The relay is not expensive. I can't remember the figure at the moment but I'm certain its under $15 from a good auto parts store like NAPA. This is your call though...the pump could go out again at a bad time, but in reality that's part of the accumulator's purpose.

[Guest DTerry]

I suppose the pump could have been shut down for a while, but that doesn't explain why I got six pumps before depletion and the pump started right back up. Or maybe it does?

I have a half-dozen or so spare relays, so I might as well change it and see what happens next.

I hate intermittent problems. Why can't it just quit and be done for? Nahh...that would be too easy.

[Jim]

I have found the most common problem with these symptoms is the pressure switch. It is located just above the pump motor in front of the accumulator. Remove the connector on the pressure switch and look inside for any signs of brake fluid near the pins. Even one very small drop means the switch is leaking. I have a good one if you need one. I can be reached at jfinn@cpinternet.com

[Guest EDBS0]

I have seen old "wet" brake fluid boil due to under hood temperatures in hot weather. The pump runs constantly because it can't build pressure and the red light is quickly lit.

A brake fluid flush will fix this easily.

[Guest DTerry]

Y'know, I thought about that. It hasn't been flushed in over 2 years, and it was a hot day - son driving it on county roads, multiple stops. I just got back from a test drive, and the brakes are fine; excellent feel, excellent stop. Brake tests indicate that the accumulator may be a little weak, but it's only a little over 2 years old.

Jim, the pressure switch is bone-dry, and I'm relatively sure it's okay. By the way, I got it from you a couple of years ago.

I'm gonna assume it's okay for now, flush it first chance I get, and see what happens next.

Thanks for the suggestions, folks.

[Jim]

If the pressure switch is good the other thing I am seeing more and more lately is the pump motors are getting bad. This is from age but I think more the cause of the motor getting bad is they are running more than they should. A weak accumulator causes the motor to run almost everytime you step on the pedal because the "reserve" is not there. With a new accumulator you have a reserve of a couple of applications of the brake pedal before the pump runs but with a weak one the pump runs more often.

If the red and yellow lights are on and and won't go off, with the key on try tapping on the motor with a metallic object. This will jar the motor enough so the probably bad brushes make contact and the motor will start.

[Guest DTerry]

That's quite a fifty...one?...Chevy you have there, Jim. Looks like a real go-fast.

Drove the car 25 miles to the city today, and quite a bit of city driving in Terre Haute - just to check out the brakes before my son drives it again. Absolutely perfect. Beats me.

By the way, the yellow light has been on for over four years. Someday I'll get around to that, but anti-lock just isn't important to me. It hasn't made the top 25 on the priority list yet.