“Brakes” light constantly on in instrument cluster

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1st73mach

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Hey guys so I have been working on my mod one and I got my instrument cluster to work with all the lights and stuff and I noticed that the brakes light has been constantly on. Is this only supposed to turn on with the parking brake engaged? I have never activated my parking brake so I don’t know if it works at all. What wires should I locate to see if I can get this light to shut off and work properly? It stays on when the car is running and when I just have the key in accessory power.
 

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KevinP

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Two most likely possibilities are (1) brake switch on combination/proportioning valve is broken, or (2) that the piston in the proportioning valve is actually stuck (often happens after bleeding brakes if you don't use the tool to lock the piston) and the switch is doing its job.
 

KevinP

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Also to clarify, that light is has nothing to do with the parking brake. It is a brake fault light to let you know there is something wrong with the main hydraulic brake system, and is triggered by the switch you can see with the wire going to the proportioning valve
 
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The light comes on when there is a front/rear in-balance in the hydraulic braking system. It can be triggered by bleeding the brakes as well.
The procedure to recenter the Pressure Differential Valve and turn the BRAKES warning light off is in the Shop Manual, section 12-01.

Pressure Differential Valve.jpg

Description and diagram:
Pressure Differential Valve2.jpg
 
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The first thing to do is to make sure that some part of your brake system hasn't failed, like a hole in a brake line, or a bad wheel cylinder or caliper. Check the brake fluid level in the master cylinder. If there is nothing wrong with the brake system then troubleshoot the brake warning switch/proportioning valve.
 

1st73mach

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Okay so my brakes work, everything is sealed and no leaks anywhere. Where can i locate this pressure differential valve? Is there a wire that is supposed to lead to this part? And if its not plugged in, could this cause the light to be on at all times? This whole car has wires that arent connected where they should be so i wouldnt be surprised if the wire isn’t attached to it. What color wire should i be looking for?
 
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The brake proportioning valve with the switch you are looking for is right under the brake master cylinder. Just follow the two brake lines that go out of the brake master cylinder and a little beneath it you will see it. Here are some photos of the valve with the switch:
 

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You have already received in this thread some great ideas on what is wrong, and how to fix it. So I won't go into any deep details. But, I also feel it is your brake line Proportioning Valve that needs to be re-centered AFTER you determine the problem with the brake hydraulic system that caused the Proportioning Valve to go off center to begin with. This could be a leaking component (brake line, wheel cylinder for drum brakes, caliper seal for disc brakes, or even an internal or external (or both) leak with the Master Cylinder.

In the event you do end up pulling the calipers for rebuilding or replacement, please be aware they can be installed on the wrong wide of the car. Attached is a graphic that shows why it is important to get the calipers on the correct side of the car. In short, if they are on wrong you will never be able to bleed the air out of the caliper(s).

1648739569848.png
 

KevinP

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The light comes on when there is a front/rear in-balance in the hydraulic braking system. It can be triggered by bleeding the brakes as well.
The procedure to recenter the Pressure Differential Valve and turn the BRAKES warning light off is in the Shop Manual, section 12-01.

View attachment 61832

Description and diagram:
View attachment 61833
The valve often gets stuck if the o-rings break down and you need to rebuild. There are a few You-tube videos how to do this (one from WCCC but is for the 69-70 switch, but process is the same) and you can get the kit here: https://www.musclecarresearch.com/valve-kit-kh
 

KevinP

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The valve often gets stuck if the o-rings break down and you need to rebuild. There are a few You-tube videos how to do this (one from WCCC but is for the 69-70 switch, but process is the same) and you can get the kit here: https://www.musclecarresearch.com/valve-kit-kh
You also should get the switch lock tool to use when bleeding. You screw it in in place of the switch during the bleeding process so the piston can't move. https://www.musclecarresearch.com/brake-valve-tool
 

1st73mach

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Alright sorry to leave everyone hanging on this one, ive been busy with life outside of cars but im back and on top of things lol. So i believe my calipers are in the correct orientation, i found the connection on the distribution block and it is connected, light turns off with it disconnected. I have a thought that there could be air in the lines and it’s triggering the light but im uncertain. I checked my fluid level and it seems a little low but there is fluid in it. I have pictures to include as well. Could somewhat low fluid trigger the light?
 

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Low fluid level won't cause the light to come on unless it sucked a bit of air into the system and, frankly, yours looks low enough that it may have.

Bleed the brakes. If you are a DIY shade tree mechanic I suggest getting some speed bleeders. It makes the brake bleeding job about 10 times, maybe even 20 times, easier.
 
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Agree with above the fluid is waaaaaaay too low. The big side of the master cylinder is for the front brakes, and the small one if for the rear. On the front side the hole that feeds the piston that is inside the master cylinder is on the back of the master cylinder, but it is usually like a raised area of it. You are so low that it is almost uncovered, and I am sure that when you hit the brakes, and the car nose dives, and inertia pulls everything forward, it is uncovering the feed hole and you are getting air in there. That is most probably why you have your brake light on. First thing is to fill that master cylinder with brand new brake fluid. You may not need to bleed the brakes to get the light to shut off and get everything working normally, but looking at the condition of that brake fluid, I would bleed the whole system of that old brake fluid as it is contaminated. The fluid level needs to be basically almost to the top of master cylinder, you also need to push the rubber gasket back into the cap, that gasket should look completely flat. The rubber on the gasket is designed to move down on the MC as you the brakes wear and your fluid level goes down, to take up the air space, it should never get to the point where your is at where both parts of it are completely deployed to their farthest reach.
 

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1st73mach

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Okay so i took the car out of the storage unit and noticed a small puddle of brake fluid where my passenger rear tire was on the ground. I had also taken the car to get looked at by my personal mechanic who works at a dealership, unfortunately the bossman threw a fit that my car was getting looked at and i wasnt able to have anything done other than he generally look it over and i asked him to top off my brake fluid. On the way back to my unit i was able to feel the air in the brake lines and i now for sure know i have a leak. It is coming from the drum and not the line I believe… but i also have never seen the inside of my rear brakes, all i know is the overlap where the front of the drum meets the rear has a line of brake fluid coming out dripping onto my rim, down the tire and puddling. Im assuming this is the cause of my brakes light being on from what you guys have told me?
 
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If you have brake fluid coming out of the drum, then the brake cylinder on that side of the car is shot and will need to be changed. If one side is shot then the other side can't be far behind, so the best thing would be to change both sides at the same time. The rear brake lining will also be completely drenched in fluid and will need to be changed too. At a minimum you will need to change the brake shoe on that side and the brake cylinder on that side. Brake shoes should be changed in pairs, so you should do both shoes at the same time. You should also have the drums turned, or buy new drums when you put new shoes on it. I have no idea how much you want to spend on the car, but on these old girls, the best bet is to do a complete rebuild of the rear brakes. Again, you can do the minimum and just do that sides brake cylinder and brake shoe and get the car back on the road for maybe $40, or you can do both side cylinders, shoes and turn the drums or buy new drums for maybe $50, or go all out and get everything and completely rebuild the rear brakes for about $120 with new drums. This assumes you will do all the labor. All you should need to do a complete rebuild is here:
1- brake shoes: under $20 at rock auto
2- new drums: AC Delco Professional under $23 each rock auto
3- wheel cylinders: under $10 each at rock auto
4- drum brake hardware kit: under $6 at rock auto
5- drum brake self adjuster kit: under $6 at rock auto

For how little the parts are you might as well change everything and do it once and forget about it for the foreseeable future.

One thing to note is that most of these cars use 2 left side wheel cylinders. So, if you buy one left and one right, the right one will not work.

If you are doing the rear brakes you should get the tools, Under $15 at you local Harbor Freight:

Really good video on how to do your rear brakes:
 
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If you have brake fluid coming out of the drum, then the brake cylinder on that side of the car is shot and will need to be changed. If one side is shot then the other side can't be far behind, so the best thing would be to change both sides at the same time. The rear brake lining will also be completely drenched in fluid and will need to be changed too. At a minimum you will need to change the brake shoe on that side and the brake cylinder on that side. Brake shoes should be changed in pairs, so you should do both shoes at the same time. You should also have the drums turned, or buy new drums when you put new shoes on it. I have no idea how much you want to spend on the car, but on these old girls, the best bet is to do a complete rebuild of the rear brakes. Again, you can do the minimum and just do that sides brake cylinder and brake shoe and get the car back on the road for maybe $40, or you can do both side cylinders, shoes and turn the drums or buy new drums for maybe $50, or go all out and get everything and completely rebuild the rear brakes for about $120 with new drums. This assumes you will do all the labor. All you should need to do a complete rebuild is here:
1- brake shoes: under $20 at rock auto
2- new drums: AC Delco Professional under $23 each rock auto
3- wheel cylinders: under $10 each at rock auto
4- drum brake hardware kit: under $6 at rock auto
5- drum brake self adjuster kit: under $6 at rock auto

For how little the parts are you might as well change everything and do it once and forget about it for the foreseeable future.

One thing to note is that most of these cars use 2 left side wheel cylinders. So, if you buy one left and one right, the right one will not work.

If you are doing the rear brakes you should get the tools, Under $15 at you local Harbor Freight:

Really good video on how to do your rear brakes:
As usual from you, a very good write-up. Do it once, do it right!
However, I doubt the offer of the T shirt is still valid!
 
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