Brake Warning Light - HELP!

[PurpleBeeper]

If you can push pedal to floor slowly and you have no leaks you have a bad master cyl

That's my thinking. I think my "new/rebuilt" master cylinder is no good and I also might have a problem with my metering valve (maybe?). I haven't pulled the wire yet, but I will this weekend just to be sure I don't have short. The problem I'm having today is that both NAPA and Advance are out of stock for my master cylinder.....what the heck.

 

[Sixpactogo]

I had the same issue with my 68 Charger when I replaced all the brake parts and upgraded to front discs. I was able to vacuum bleed all four and had a good pedal. The brake light was on and the rear brakes would not lock up. I also tried the brake stomp trick that did nothing. The problem ended up being in the new proportioning valve. After trying two different valves from inline tube, I contacted Cass at Dr Differential and he sent me one from a supplier he uses and it worked perfectly. Having said that, I don't think your master cylinder is the culprit here. I have two of the new failed proportioning valves to prove it.

 

[mccoymail]

any updates? I feel invested in this and would like to know what you found.

 

[PurpleBeeper]

Well....I bench bled a new master cylinder & put it in and the pedal is still soft & light on. I'm sure I have some air in it since I've only gravity bled the lines for 15 min. I'm looking for one of those tools that holds the proportioning valve pin-whatever down while bleeding the brakes. Anybody know where to get one? I saw a picture and it looked like maybe a 2" x 3" piece of sheet metal with a notch on one side to slip under a notch on the little nub sticking out of the proportioning valve. The piece of metal is doubled over so when it's in place it sort of acts like a spring keeping the little nub pulled out. My next step was to put the OEM metering valve & proportioning valve back in but stupid me threw them away. I'm starting the second-guess the quality of the replacement brass valves I got with my stainless brake lines.

 

[Sixpactogo]

If you got your brass valve from Inline Tube, there is a very good chance that is where the problem is. I have two new ones from them that failed. When I spoke with Cass at Dr Differential, he told me that he has had lots of guys call him with the same problem and all had bought their valve from Inline Tube. I don't know why the failure rate is so high but like I said I have two of them.