Disc conversion

Got the Front drum brakes removed and the Front Disc brakes installed on my 72 Skylark (spindles, rotors,calipers, prop. valve(gm) and I have a question. The back brakes took a little time to bleed, front bled fine. The brake light came on in the instrument cluster and has not gone off (haven't driven other than around the yard yet). Any ideas why? The pedal is firm and the car stops fine.

 

Question: have you changed the master cylinder to a disc/drum unit?

 

Yes. MC changed to disc unit. Power booster not changed.

 

You might have an air bubble in the proportioning valve. You can either bleed it from the proportioning valve by cracking the lines at the valve, or stomp the brake pedal really hard a few times while bleeding to force the bubble out of the valve and down the lines.

-Josh

 

Pretty much what the guy above said. I've done this on several cars with fresh systems. Open one or both rear bleeders JAM the pedal to the floor, close the bleeder(s), repeat a few times then do the same to the front. This has always fixed it for me but your mileage may vary.

regards

 

The "combination valve" as GM refers to it seems to be the most likely problem. I did notice that you are still using a drum/drum booster. The disc/drum booster is different from the drum/drum booster. That may dontribute to some of the issue.

 

is the wire from the prop valve brake warning system plugged in?

 

Wires are plugged in and working properly. I will be working on it again tomorrow night and will re-bleed. Thanks for the ideas.

 

I ran into this problem after I swapped the discs from my totalled Skylark to my new one. I bled the brakes several times and the light didn't go out until I backed down the driveway and slammed the brake pedal a few times and the light went out.

 

There is a rod that goes from the bottom of the sending unit ont the porp.valve. I have had to remove it and reset the switch manualy in the past to get the light to go out after it was activated.

 

wne u slam on the brakes, what i think u are doing is releasing the bleed plunger/switch in the prop valve. chassis manual explains it.

 

So what happened?

 

re-bled from the valve, then each wheel -no change. Drove back and forth in the shop yard. After 4 hard stops, the light went out. The brakes feel good. The pedal is right there and is smooth.

Thanks to everyone for the advice

Craig

 

just wondering did you use a conversion kit or junkyard parts? I'm looking to do this same thing soon and would love to know any perspective you have on it since you just finished.

Thanks,
Charlie