I was on my way to work today when my brakes suddenly failed... sort of. The pedal went just about 90% of the way to the floor then finally met some resistance and I got just enuf braking power to stop at low speed. After a quick check of the resevoir I determined that I don't have a major leak.

I searched this site for a bit and saw a post by 64elcamino explaining how badly adjusted rear brakes can cause a pressure differential in the system. so, I took the velle out, got up some speed in reverse, slammed on the brakes, and got pedal! Lots of it too, just like normal. Same thing would happen going forward. As long as I hit the brakes hard and fast, they reacted like normal. If I simply try to slow down, the pedal sinks almost all the way and my BRAKE light comes on. Any idea what could be going on? If there is air in the system, why do its compressibility effects only affect performance over a (relatively) long time? And how could just a finite amount of air enter the system during my commute?

thanks,
Dan

Sounds like what happened to me with a bad master cylinder.

I was able to stop by pumping on the pedal. Once every 10 pump or so, I'd get pressure. That was a hairy ride home on the highway. smile.gif

Tim.

Dan, I'd bet my last 32nd of tire tread you have a bad master cylinder. Very common symptom, do us a favor a don't try to get by a few more days by pumping the brakes. Not enough of us enthusiasts left to lose one over something so easy to fix.

Do you recomend replacing any other components, such as the combination valve or power brake booster at the same time? I really don't like these parts failing on me, not a happy surprise. The chevelle was originally all drums brakes and the PO put discs up front (probly junkyard) about 6 years ago. thanks for your help.

Dan

If you didn't change the combination valve you should, everything else should be OK.

Ok, I replaced the m/c and everything is happy again in chevelleland. Just wanted to follow-up for anyone searching in the future with my symptoms. Thanks again eveybody.

Dan