1996 GC 3.8L

Intermittant loss of braking power. Some times when I apply the brakes there is a very hard feel to the pedal, there is a kugugugugugug like sound coming from the left front, and there seems to be almost no braking power. I have to stomp on the pedal very hard to get the vehicle to stop. Pumping the brake does not help because there is the same hard feeling with every pump. Once the vehicle is stopped and then moving again the brakes will work and feel fine until the next time this happens. About a minute after this happens the ABS warning light comes on and stays on until the vehicle is turned off. When the vehicle is turned on again the ABS light will be lit through the startup check and then turn off.

This has happened very infrequently over the past four months but has happened 5 times in the last two days. I almost piled into the back of another vehicle today at a stop light when this happened. FREAKY

The brake fluid is right up where it should be. There are no fluid leaks. I have had a gazillion vehicle and some with various brake issues but nothing like this.

Any suggestions?
Master cylinder?
ABS?
Proportioning valve?

 

I don't know how to fix it, but it sounds like the ABS is being activated which will limit your brakeing.

It should be possible to disconnect the ABS. I have no ABS on my van.

 

Faulty ABS sensor is one of my suspects. How can I test this?

 

First thing I would do is check the ABS module for stored or active codes. And go from there.

 

I have a generic OBDll code reader but it doesn't read ABS codes. If I remove the two ABS fuses from the engine compartment fuse panel, will this disable the ABS until I can get an ABS code reader and solve the problem?

 

I believe the issue is now resolved. I removed the ABS fuses from the fuse box under the hood. The dash ABS light came on but the feel and performance of the braking immediately normalized. I drove the vehicle like this for a couple of days to further validate the ABS hypothesis. I didn't bother retreiving the ABS codes because I could not beg, borrow, or steal an ABS code reader. I removed the wheels to check and clean the ABS sensors. I was hoping that the problem was created by something on one of the sensors interfering with the sensor's ability to detect the movement of the tone wheel. Sure enough the first sensor I checked had bits of ferrous material stuck to the surface facing the tone wheel. The tone wheel was undamaged. The other sensors and tone wheels check out ok. After cleaning, reassembling, and reinstallation of fuses, the test drive braking was normal (ABS activation with hard braking on gravel and solid non-ABS braking on dry pavement).

Fortunately a simple cheap solution.

 

Glad to hear that you solved your problem.