brake pedal goes down and Brake lights come on.

[frijoli]

When sitting at a light with my foot on the pedal, it gets soft and moves closer to the floor. Both the brake light and the ABS light come on. If I lift my foot and step on the pedal, it has full pressure against my foot again, but will allow the pedal to get soft again.



Is this an ABS issue or just a master cylinder rebuild? I just bought this 1993 4x2 truck. Need suggestions.

Thanks,

Clay

 

[Paychk]

Welcome to the forum!



The master cylinder is most likely the culprit, it can develope a leak between the reservoirs or a leak into the booster. I would recommend a quality new master cylinder over a remanufactured. The quality brands are Raybestos, Wagner, Bendix

 

[frijoli]

Thanks for the welcome.



I suspected the master cylinder, but I've not worked on an ABS vehicle before.



Thanks, I'm loving the diesel sound and torque!

Clay

 

[Paychk]

Clay



The ABS valve could also cause this problem (not as often) what you can do to test the system is go to a good parts store and get two brass plugs for the master cylinder. Disconnect the lines from the master cylinder, plug the ports and test. If it still leaks down, then it is in the master. If it doesn't leak, reconnect the line to the rear brakes and test again if it leaks then it is probably the ABS valve.

 

[frijoli]

good thought. I'll try that.

Clay