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post #1 of 7 (permalink) Old 05-01-2017, 09:28 PM Thread Starter
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Brake system and "Brake" light.

Okay, so researching this problem has taught me a lot, but I wanted to ask you guys for your experiences.

I bought this 94 V6 Automatic Camaro as a project. It was only $650, but it had a lot of small problems to fix. The brakes were bad, so I knew I'd have some work to do. One of the lights on the dash that was illuminated was the "Brake" light. I had assumed this had nothing to do with the brake problem as I thought this only had anything to do with the parking brake.

The pedal went all the way to the floor, but it didn't seem to be leaking fluid. I figured the system just needed to be bled. I jacked it up and started with the right rear wheel. I found out then that the rear brakes weren't engaging at all. After some research, everything I'd read suggested it was the master cylinder. I bought a new one, bench bled it, and installed it. Pedal was still soft, but I wasn't getting much air out of the bleeder screws. I figured I needed to drive it around the block, hitting the brakes hard and often to work the air to the ends of the lines. The good news was that I did now have rear brakes. The bad news is that the left rear cylinder was leaking. The drum was full of brake fluid.

Next time I'm working on it, I replace both rear wheel cylinders and once again bleed the system. I primed the cylinders before installing them. I got some air out when bleeding, but nothing significant. Pedal still soft. Tried driving the car again to work the air back, still not getting any air. Pedal still soft. Gave up and worked on other things for a while.

I decide to go back to the brakes. Since it still acted like it had air in the lines and the fluid was dirty anyway, I decided to flush the entire system. I made sure the reservoir was full, attached the "one man brake bleeder" tool to the bleeder screw and loosened it. I figured out it takes 25 full pedal strokes to fill that little bottle. Each time, I would empty it and top off the reservoir. Then repeat. I did this for each wheel until I saw clean fluid. For the right rear wheel, I got about 50 pedal pumps of nothing but air between the dirty and clean fluid. No air in the others, but at least now it has clean fluid. Pedal firmed up. Brakes work great. I think I'm done at this point.

Fast forward to the other day when I decide to remove the console so I can fix the "Brake" light issue. Come to find out, it's a single wire going to the switch at the bottom of the parking brake lever. When it's down, the switch is open. When you raise it, the switch closes and grounds that wire, causing the light to go on. Theoretically, you could just unplug that and make the light go off. But my light was still on. Did some google searches and apparently, there are two other sensors that can cause that light. One is the fluid level sensor in the reservoir. The other is a sensor in the ABS module/proportion valve. I decide to check those, and turns out, this car has neither that I can tell. At least not like the one in the console. There is NOTHING in the reservoir. I know because I just replaced it. The old one didn't have it either. There are wires going into the ABS module/proportion valve, but none that are a single wire like the brake lever. Also, none of them look like a sensor. They all just look like harnesses that work the ABS system. Plus, the abs system checks out. No ABS INOP light. So anyway, one of the things that can make that light illuminate is disproportionate pressure between the front and rear brakes ( according to the google searches ). That was a huge problem when I bought the car, but I fixed it all and the rear brakes work now, but the light is still on.

It looks like there are only 2 possible things going on.

1: There is air in the ABS module. My Haynes manual says to bleed it with the rear and front bleeder screws. The problem is that I don't see any bleeder screws. One link through google said to bleed it at the lines. Basically loosen the lines on top, one at a time, as you would a bleeder screw. But I don't think the Haynes manual would call the lines bleeder screws. Does anybody have a picture of the location of the bleeder screws?

2: If the light was on for too long, the sensor can be stuck. People have reported that even after fixing their problem, the light stayed on. Usually after going too long without fixing the issue. The solution is to go out now that it's fixed and just abuse the brakes. Build up speed, and just slam the brakes hard. Something about the pressure over the sensor will unstick it.

Can anyone here confirm either of those two issues? Does that brake light activate because of low fluid or air in the ABS unit?

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post #2 of 7 (permalink) Old 05-02-2017, 06:54 AM
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First, go to the following link and download the 94 factory service manual Haynes is a pos. www.mediafire.com/?40mfgeoe4ctti

Then go to the following link and download the 4th gen camaro parts book. The abs brake modulator assembly diagram will show where bleeder valve is, at least 1 of them. I'll assume the other is on the opposite side of modulator. Index of /pics

Brake light can come on because of uneven fluid pressure detected by modulator assembly, and/or, a problem with the electronic brake control module. The ebcm is located under ip next to lh hinge pillar, just above pass through grommet.

Can't say if slamming on the brakes will shut the light off.

Last edited by cocobolo95; 05-02-2017 at 07:00 AM.
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post #3 of 7 (permalink) Old 05-06-2017, 05:57 PM Thread Starter
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Quote:
Originally Posted by cocobolo95 View Post
First, go to the following link and download the 94 factory service manual Haynes is a pos. www.mediafire.com/?40mfgeoe4ctti

Then go to the following link and download the 4th gen camaro parts book. The abs brake modulator assembly diagram will show where bleeder valve is, at least 1 of them. I'll assume the other is on the opposite side of modulator. Index of /pics

Brake light can come on because of uneven fluid pressure detected by modulator assembly, and/or, a problem with the electronic brake control module. The ebcm is located under ip next to lh hinge pillar, just above pass through grommet.

Can't say if slamming on the brakes will shut the light off.
Okay, I downloaded the parts book. Sucks there's no table of contents at the beginning to help narrow down which of the 1395 pages has the parts I need...

When you say the EBCM is located under the IP, what is the IP? I'm not familiar enough with the website lingo to get that acronym.

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post #4 of 7 (permalink) Old 05-06-2017, 07:01 PM
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IP= instrument panel Parts manual should have a group listing that tells where most everything is. When you open parts book, it's on the left side of pdf window. Brake system is in group 4. GM parts books are organized into groups. Group 0 is engine group 1 = cooling system & drive belts group 2 = electrical group 3 = cruise, air pump, ecm & wiring etc. group 4 = transmission & brakes group 5 = rear brakes, axle, drive shaft, & wheels group 6 = front suspension, steering gear, steering column group 7 = rear suspension & bumpers group 8 = front sheet metal, hoses & pipes, spare wheel, blower group 9 = instrument panel, instrument cluster, stereo systems, a/c, & antenna group 10 = instrument panel part 2, mirrors, windshield, wipers,console, entry system, weatherstrips group 11 = seat hardware, interior lamps group 12 = moldings, stripes rear sheet metal, roof hardware group 13 = convertible top group 14 = folding top assembly, trim, seat assembly, inflatable restraint, seat belt hardware group 15 = rear seat, carpet, floor Every GM parts book is organized with this numbering system. At least up to 2002.
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post #5 of 7 (permalink) Old 05-06-2017, 07:03 PM
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Sorry again for everything in 1 paragraph. Quick reply is not working for me. When I use full editor, it jumbles everything into one big paragraph.
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post #6 of 7 (permalink) Old 05-06-2017, 08:40 PM Thread Starter
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Thanks for the reply. I actually found it not long after I posted that. I just kept scrolling up from the bottom until I saw the brake system. I think it was page 798 or something like that. I still don't think I understand what you are saying though as for using that parts book. I saw no "group listing". It was just one large PDF with nearly 1400 pages.

The good news is, I found the bleeder screws. There was no air though.

As for the slamming the brakes, that might actually work now that I found the problem. It is in deed the proportioning valve. It apparently works because there is a sliding valve in there that when there's a leak in either the front or rear, that allows the pressure from the other direction to push the valve all the way to the other end, triggering the light. The way to tell is to unplug the sensor. The light went off. Apparently, if that valve is all the way to one end and you fix the brake problem and the pressure is equalized, it will stay on that end as there is no pressure to push it back to the middle. Equal pressure means it doesn't move.

Some have said though that you can do a bleed with the key in the on position and see if the light goes off when you open either a front or rear bleeder valve. This will create uneven pressure that will move the valve. You have to do it with the key on though so the person pushing the pedal can see if the light goes off and then comes back on when the valve moves to the other end. If so, you have to then go to the other end of the car and do the same. Only this time, the person in the car yells when the light goes off and you have to close the bleeder before the valve moves to the other end and the light comes back on. I'm going to try this tomorrow.


Last edited by Black Bullit; 05-06-2017 at 08:57 PM.
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post #7 of 7 (permalink) Old 05-13-2017, 09:06 PM Thread Starter
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Okay, I tried opening just one bleeder valve and pushing the pedal gently to see if the light would go off. It did not. So either that trick does not work, or I was on the wrong end of the car. I didn't try a rear bleeder valve yet. Instead, I decided to go ahead and flush those two bleeder screws on the ABS module. The fluid coming of those was still pretty dirty. While I didn't get any noticeable air coming out, I did get quite a bit of contaminated fluid out. The light was still on and I was at a loss. Everything I'd read said the light should go out once you fix the brakes. Mine are fixed, but the light was on.

Fast forward to today. I started the car to drive it around the house to the front yard so I can buff the paint. Guess what? The brake light was off. Even though I flushed those bleeder screws out and the light stayed on, something must've happened because it decided to finally go off.

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