1999 Intermittent Anti-Lock Issue

[friendlydan1]

I have a strange intermittent problem with my Astro's brakes. Anti-lock warning light is on. No fluid leaks that I can see. 95% of the time all is good...then suddenly I will feel my pedal drop about a half-inch...and I loose part of the brakes completely...Feels squirrelly to handle so I think it's the rear brakes literally dis-engaging. It will stop but not as it should....then no problems with it for a day or so. Anyone else have this issue? Sure wish it just did it all the time....versus just once in awhile!

[paulo57509]

I don't have this issue but it's not uncommon from what I understand.

I recall reading on the Chevy Talk forums that a rusty reluctor ring at the wheel(s) can cause issues like this. Also mentioned are bad speed sensors among other things.

Instead of throwing parts at it needlessly, the first step would be to retrieve the ABS trouble code when the ABS light is on.

However, some generic code readers will read ABS codes, some won't. Perhaps Autozone or a similar store can read them for you.

[Astrofarian]

X2, That^^^ Totally agree with Paulo there. The rings and sensors are the parts that are the most "exposed" to damage and the elements. Start there.
If you have an independent brake-specialty shop nearby it may save some headaches to let them pull the codes and recommend a course of action. Expect to pay them for at least an hour's worth of their time and be up front about letting them know that you plan to repair it yourself. Some shops/techs will work with clients this way, some won't. But if they will, you may have to purchase your parts through them as part of the deal.
Depending on your experience and comfort-level working on ABS systems, this may be your best option. They can always take over if you find yourself in over your head.
-M!ke-

[AstroWill]

With the ABS light on it's seeing a problem, read the codes to find out what problem it is detecting.

[friendlydan1]

This problem could be a huge expense to fix. The brakes are fine for a week or so...then one day I hit them and the pedal drops and I lose most of the brakes. Dangerous as hell so I haven't been driving it much. Then the problem goes away for days at a time.....

But....if I just remove the ABS main fuse and take it out of operation...won't that stop the intermittent craziness with what I feel almost certainly is a malfunctioning Brake Pressure Modulator Valve? I don't mind if the anti-lock feature is not there if the brakes just work normally!

[Leeann_93]

I don't know that the pedal intermittently dropping is a BPMV problem. It sounds more like a hydraulic problem - when's the last time you fully bled the system, getting out all the nasty fluid until it's clear and bubble-free at the calipers?

Most BPMV problems come with a groaning sound under the driver's seat (where the BPMV is) and a nasty pulsing you can feel through the pedal. On my '02, I had gotten completely used to immediately pulling my foot off the pedal when I heard groaning and felt pulsing, then immediately reapplying the pedal, which overcame the BPMV problems and allowed me to brake normally. I never did get around to reflowing the solder joints.

If it is the BPMV, pulling the ABS fuse should bypass the problem. But if there's air in the ABS pump or anywhere else in the system, that won't help.

[AstroWill]

This problem could be a huge expense to fix. The brakes are fine for a week or so...then one day I hit them and the pedal drops and I lose most of the brakes. Dangerous as hell so I haven't been driving it much. Then the problem goes away for days at a time.....

But....if I just remove the ABS main fuse and take it out of operation...won't that stop the intermittent craziness with what I feel almost certainly is a malfunctioning Brake Pressure Modulator Valve? I don't mind if the anti-lock feature is not there if the brakes just work normally!

Read the codes first. But sure you can simply pull the fuse and see if that makes any difference. Either way gives you a place to start.