Fun with the 'Brake' warning idiot light.

[Drew]

1991 Firebird Formula 350, stock four wheel disc break system, somewhere around 120,000 miles.

So ok, I parked the car in my parents garage with an intermittent undisclosed transmission problem, no other problems what so ever. Someone decided they wanted to move the car to the other garage so they fired it up and moved it in the other garage in my absence. After removing the car from storage, the transmission issue went away and suddenly the 'Brake' warning light is lit up full time. If I disconnect the plug from the top of the proportioning valve the light goes off. When I bought the car it had an aftermarket cast iron master cylinder vs the stock extruded aluminum piece. Since I've had an extra OEM master cylinder laying around, intended for the swap I took advantage of the Brake problem as a chance to switch the parts. I bolted on the new master cylinder, and started bleeding the breaks. I got distracted and was reading in the Big Book of Fbody (Helms/GM manual) about the possible causes for the light to come on. With my set of circumstances the most likely cause that fits the conditions is that there was an imbalance in pressure between the front and rear brake circuits. I can only imagine that my mom, in typical Incredible Hulk fashion, over exerted the brake peddle trying to overcome the transmission issue and forced the sensor in the proportioning valve to go off center and trip the light. Since apparently the switch is not servicable and the entire assembly has to be changed, and I'm a cheap ass, I don't want to spend $120 for a new prop valve from the dealer, I'm looking for potential work arounds.

I've read on www.thirdgen.org that the sensors can stick, and be impossible to flip back. Also I've seen it mentioned that compressing the pistons in the calipers can reverse the condition and trip the switch back to neutral. I figure there's a 20% chance that completing my bleeding job will fix the problem. I've never disassembled one of these prop valves, has anyone here been through that? Can the switch be manipulated with the valve torn down? $120 to turn off an idiot light seems excessive, but I'm not into just leaving the pigtail disconnected either. So any ideas?

[Slush]

I have mine disconnected since i no longer have a stock gauge cluster. Besides the retarded light coming on, will it have any effect on how the brakes function? If it doesn't, then why not leave it off.

I think you can disassemble it but i'm not too sure of that. It would make sense if one set of brakes was working more than the others that the light would be triggered, but it should reset once the condition if righted, unless yours is stuck. Last ditch effort, whack it with a rubber mallet (not metal hammer) to see if that unsticks it. Sorry if i rambled and said nothing important :)

[Meatman]

From what I have heard you have to take that sensor out of the prop valve to get it to go back. I can rob the one off my v6 parts car before I send it to scrap if you would like.

[Drew]

Thanks for the offer, but I've got at least two extra prop valves in storage somewhere. The problem is they're from base model cars with disc/drum brakes. At least I should be able to tear one of them down and figure out how to unstick the switch. There's still a chance that all I need to do is finish bleeding the brakes and stand on the pedal and it might reset. I'd leave it disconnected but I believe in fixing problems correctly. Even if the car was just a daily driver beater, I'd fix it right, even if it does cost $120 for the part. I just don't always take the book seriously when it says something can't be serviced. Usually that's code for, it's faster to replace the assembly and charge more money for it, then to have a service tech tear it down and fix it.

[drek_67045]

well like my computer i fixed it myself versus hp telling me yet again its my motherboard and i need to send it in

[ddhawkfan]

Usually that's code for, it's faster to replace the assembly and charge more money for it, then to have a service tech tear it down and fix it.

not necessarily, thats like rebuilding wheel cylinders, pointless. go buy new, and save time. vs bringing it to me and tellin me to rebuild them and i'll charge ya X amount of time to pull them and X amount of time to rebuild them vs just the original X amount of time to remove them and reinstall them. and with labor rates "high" (i state that being a smart ass because labor rates in KS are CHEAP) its cheaper to just buy a new one.

[roostmeyer]

IMO, I'd just leave it disconnected. On the thirdgen cars the light will not trip until there is air in the lines, completely useless.

[Drew]

Yeah but I'd know and I'd see it everytime I pop the hood. I'll get around to fixing it one of these days and post back.