I'm thinking that as well. Funny thing is that I have no diffeence in pedal pressure or pedal travel to actuate the brakes. I don't know if we use a dual piston master cylinder or not, but if there was an internal leak, you'd think the brake pedal would feel different, travel farther to actuate whichever system is still functioning. I can get a new master cylinder from Rock Auto for about $60. Then I gotta figure out how to bleed the system properly. PIA!

 

Make sure that leak trail you see isn't coming from a leaky seal from the reservoir directly above. I say that because I'm seeing an oil/fluid stain (run) on the lower half of the master cylinder mount flange, and that wouldn't be coming from the rear master seal. Sure would hate to go through all the trouble of replacing the master, if that's not really what's leaking.

 

I'm going to clean it real good and keep a watch on it for a few days to see if I can pinpoint the leak. The wiring diagram shows the Brake light being controlled from the brake combo switch which is normally open and closes with unequal brake pressure. What does not make sense is I have no difference in braking ability.

 

Here's what I have found out. A normally open switch in the " brake combo valve" will close when it detects unequal brake pressure. This turns the dash Brake warning lamp on. Theoretically, if the switch is normally open and the light is on (which means the switch is closed), simply disconnecting the electrical connector would make the light go off, by opening the circuit. Well, disconnecting the connector on mine does not make the light go off. I checked the switch with my meter and the switch measures open, which should indicate there is no unequal pressure detected in the system. What I have found is both wires to the switch show continuity to ground. One is supposed to be, the other goes to the cluster. I'm thinking I either have a wiring problem (shorted wiring) or the EBCM is bad. Anyone ever checked theirs to see if both wires going to the combo valve switch show continuity to ground? That would narrow it to the EBCM then. A simple check if someone would have time. It's a tan/white and black/white wire going to the combo valve. Now if I can just find the EBCM....

 

so, yesterday the brake light just went out, on its own. Today, it came back on.

 

Follow up. Here's a real head scratcher. The past few days the weather has been rainy, misty, generally wet outside. The light went off and has not been back on. Pull the parking brake, the light comes on, put the parking brake off, the light goes out, just like it is supposed to. Today it has dried up and the sun has come back out. The light turned on and has not turned off. Would you be thinking electrical problem? I would think that also if the opposite were true; wet causes light to come on; however, in this case, moisture causes the light to go out. I'm still thinking EBCM, but d@mned if I can find it.

 

My 94 had the ABS INOP light on when I bought it. The PO said that light was on the whole time he owned the car. I started a thread on the situation and will see if i can find it.

I scanned the system and all the wheel speed sensors were working fine. There was a pump motor failure code which lead me to believe that the hydraulic pump assembly under the hood was bad so I replaced it with a junkyard part. Light still on and me very unhappy because replacing that thing and bleeding the brakes was a real messy PITA.

The only thing left to replace was the ABS controller and, like you, I had to find it. Well it's behind the instrument panel above the drivers left foot. It's crammed up there and very unpleasant to access unless you're a midget.

I hit the U-Pull-It yard again and got the controller from the same car that provided the hydraulic unit. Installed the controller and I had working ABS again!

I find it pretty weird that my 94 has a LOW TRAC light. I mean, if you can't tell that the ABS is operating by the sounds and pedal feel you're pretty dense.

Looks like your car's master cylinder is toast. I've seen that weep stain many times and the cause is always the same. Replace that sucker.

The symptoms on your car (regarding warning indicator operation in dry vs. damp weather) are strange and opposite of what I'd expect.

Here are some pics of the controller.

 

Found the thread I started 2 years ago:

https://camaroforums.com/forum/93-02...ou-gone-55110/

 

Thanks! I have read that thread a couple of times because it always comes up when I do an internet search for "abs inop". I had mine scanned by the dealer and there is an open somewhere for the ABS. But, the brake warning lamp comes from the same EBCM. I can live w/o ABS, it's the brake warning I got to fix because that will fail inspection. Now that I know where the EBCM is, I can get one from a junk yard and try it. This brake warning lamp has got to be an electrical issue. The brakes work the same as the day I got it. The leak at the master cylinder is a seal on the reservoir.

 

The only thing that makes sense to me about your brake light situation is you may have a poor connection.
Then when there's humidity and moisture in the air (water is a conductor), that could be completing the connection.
Much the same as how humidity can allow a bad plug wire to jump to ground when it otherwise wouldn't in the dry air.