Dash Brake Light Issue.
Thread Starter
Instructor
Joined: Sep 2013
Posts: 175
Likes: 3
From: Palmyra NY
Dash Brake Light Issue.
1980 Corvette. I installed new brake pads and now brake light is on. A quick jab of the brake pedal does not shut it off. I just had a new master cylinder, proportioning valve and rubber lines installed. System bled with all new brake fluid. Light is on when car is started. Light goes off when the brakes are applied. When light is on it will fade and dim after awhile. I do know that stopping the car quickly it pulls to hard right. There is NO issue with emergency brake switch. Thanks. Don.
Race Director
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From: Virginia
Hopefully it is as simple as bleeding again. There's still air in the system, likely in the front left caliper, perhaps elsewhere.
Did you use a pressure bleeder? That helps. I had to tap the lines, junctions, and calipers, with a wrench to get the last of the air out. YMMV.
Did you use a pressure bleeder? That helps. I had to tap the lines, junctions, and calipers, with a wrench to get the last of the air out. YMMV.
Team Owner
Joined: Jan 2006
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From: Crossville TN
If the 1980 has the same 'distribution' block as the earlier C3's (receives brake fluid from the master cylinder), it has a shuttle valve inside which 'trips' to one side [to shut off the defective half of the brake system] when a leak is detected. During the bleeding process, that valve can trip and it will send a signal (electrical ground) to that BRAKE light bulb to turn ON. Note also that the same bulb will light if the E-brake handle is engaged.
If the E-brake is not applied, you can try to STOMP really hard on the brake pedal to get the shuttle valve in that distribution block re-centered. Try that 2 or 3 times to see if that works for you. If not (and IF you do not have another fluid leak in the system somewhere), you will need to remove the electrical switch from the distribution block and manually reset the shuttle valve to center position (this process is described in the Chevrolet Service Manual). Then you will need to re-bleed the brakes.
AGAIN this is assuming that the 1980 still has that distribution block design.
If the E-brake is not applied, you can try to STOMP really hard on the brake pedal to get the shuttle valve in that distribution block re-centered. Try that 2 or 3 times to see if that works for you. If not (and IF you do not have another fluid leak in the system somewhere), you will need to remove the electrical switch from the distribution block and manually reset the shuttle valve to center position (this process is described in the Chevrolet Service Manual). Then you will need to re-bleed the brakes.
AGAIN this is assuming that the 1980 still has that distribution block design.
Thread Starter
Instructor
Joined: Sep 2013
Posts: 175
Likes: 3
From: Palmyra NY
I think it's weird that the light is on but when you apply the brakes the light goes out. So, to replace the switch you need to bleed again? My mechanic said he bled the brakes 4 times, no leaks and no air but could not get the light to go out. He seems to think the one of the calipers up front are bad. No signs of leaks but he claims that there could be a piston(s) hanging up that could possibly be the issue. Another strange thing too is that if you leave the car idling for a few minutes, the brake light will dim. Sounds like an electrical issue?
Le Mans Master
Joined: Aug 2017
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From: Cool Northern Michigan
Yes, sounds electrical.
First, if you do end up swapping the Prop Valve Switch, GM changed design at one point. Make sure you buy the correct switch, or the harness will not fit.
No DOT3 will drain out if a "good" switch is removed. It's not under any pressure like bleeders are. Therefore, no bleeding again.
Perhaps you should snoop around under the parking brake handle and cover. But I suspect the wire connection at the Prop Valve is the issue. It should be loaded with PS fluid, tranny fluid, dirt, oil, road grime, etc = poor connection.
First, if you do end up swapping the Prop Valve Switch, GM changed design at one point. Make sure you buy the correct switch, or the harness will not fit.
No DOT3 will drain out if a "good" switch is removed. It's not under any pressure like bleeders are. Therefore, no bleeding again.
Perhaps you should snoop around under the parking brake handle and cover. But I suspect the wire connection at the Prop Valve is the issue. It should be loaded with PS fluid, tranny fluid, dirt, oil, road grime, etc = poor connection.
Thread Starter
Instructor
Joined: Sep 2013
Posts: 175
Likes: 3
From: Palmyra NY
Thank you for writing! I am tempted to remove the new switch from the new PP valve and install the old switch to see what it will do. I will check to make sure it is clean. I do not have any issues with the e-brake switch.
Race Director
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From: Virginia
And there are three grounds that can illuminate that bulb. The third is in the ignition switch. While the combination valve is most likely, it is worth confirming that pulling the valve wire turns the bulb off, and shorting it to ground turns it on.
Thread Starter
Instructor
Joined: Sep 2013
Posts: 175
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From: Palmyra NY
My mechanic told me he already did that test and no change. He told me last night while doing the parts replacements that when he clamped off the front brake lines the light went out. He believes I have a caliper up front causing some issues. So, next spring, buying four new calipers for the car and having them installed. Something must of happened when I did the pad change.
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Le Mans Master
Joined: Aug 2017
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From: Cool Northern Michigan
Remind your mechanic that only the front calipers, must have a copper crush washer installed when attaching the rubber hoses. The special washer usually comes with a set of hoses or sometimes comes with front calipers.
Race Director
Joined: Mar 2017
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From: Virginia
My mechanic told me he already did that test and no change. He told me last night while doing the parts replacements that when he clamped off the front brake lines the light went out. He believes I have a caliper up front causing some issues. So, next spring, buying four new calipers for the car and having them installed. Something must of happened when I did the pad change.
You know which caliper it is. Any reason not to try to rebuild/replace it yourself?
Race Director
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From: Virginia
Separately, yes.
Zip even has a diagram of where they go (on the front calipers). You may be able to see if they were installed, or not. Though if this problem occured after you changed the pads, I bet one of the pistons got crosseyed in the bore, or the lip seal is wonky. Use a new CSSB Inc. O-Ring kit to fix that (assuming smooth, SS lined bores).
https://www.zip-corvette.com/53-82-b...er-washer.html
Zip even has a diagram of where they go (on the front calipers). You may be able to see if they were installed, or not. Though if this problem occured after you changed the pads, I bet one of the pistons got crosseyed in the bore, or the lip seal is wonky. Use a new CSSB Inc. O-Ring kit to fix that (assuming smooth, SS lined bores).
https://www.zip-corvette.com/53-82-b...er-washer.html
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Thread Starter
Instructor
Joined: Sep 2013
Posts: 175
Likes: 3
From: Palmyra NY
Separately, yes.
Zip even has a diagram of where they go (on the front calipers). You may be able to see if they were installed, or not. Though if this problem occured after you changed the pads, I bet one of the pistons got crosseyed in the bore, or the lip seal is wonky. Use a new CSSB Inc. O-Ring kit to fix that (assuming smooth, SS lined bores).
https://www.zip-corvette.com/53-82-b...er-washer.html
Zip even has a diagram of where they go (on the front calipers). You may be able to see if they were installed, or not. Though if this problem occured after you changed the pads, I bet one of the pistons got crosseyed in the bore, or the lip seal is wonky. Use a new CSSB Inc. O-Ring kit to fix that (assuming smooth, SS lined bores).
https://www.zip-corvette.com/53-82-b...er-washer.html
Thread Starter
Instructor
Joined: Sep 2013
Posts: 175
Likes: 3
From: Palmyra NY
Separately, yes.
Zip even has a diagram of where they go (on the front calipers). You may be able to see if they were installed, or not. Though if this problem occured after you changed the pads, I bet one of the pistons got crosseyed in the bore, or the lip seal is wonky. Use a new CSSB Inc. O-Ring kit to fix that (assuming smooth, SS lined bores).
https://www.zip-corvette.com/53-82-b...er-washer.html
Zip even has a diagram of where they go (on the front calipers). You may be able to see if they were installed, or not. Though if this problem occured after you changed the pads, I bet one of the pistons got crosseyed in the bore, or the lip seal is wonky. Use a new CSSB Inc. O-Ring kit to fix that (assuming smooth, SS lined bores).
https://www.zip-corvette.com/53-82-b...er-washer.html
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
Technically, it's a "Crush Washer". And technically it's a "One-time" use.
Brake calipers are cast iron. Where the hose threads into the unit is machined but still pretty rough. If a shiny steel hose fitting were to contact that ruff cast iron, a leak is sure to follow. That's where the crush washer makes a good seal and sacrifices its form. You are only supposed to use a crush washer once. But I have reused without issue.
Don't let a parts store sell you copper washers. It's not the same. Crush washers are very soft copper.
Crush washers are still used today on modern vehicles where a rubber hose fits a cast iron caliper. The crush washer really needs a lot of torque on the hose fitting to do so. Some mechanics place the caliper in a vise and attach the hose with a line wrench and muscle it down. Then install both as a unit on the vehicle.
Note that the rear calipers do not have a rubber hose connected but instead have a flared steel line that matches the flare inside the caliper. Therefore, do not require a crush washer.
Brake calipers are cast iron. Where the hose threads into the unit is machined but still pretty rough. If a shiny steel hose fitting were to contact that ruff cast iron, a leak is sure to follow. That's where the crush washer makes a good seal and sacrifices its form. You are only supposed to use a crush washer once. But I have reused without issue.
Don't let a parts store sell you copper washers. It's not the same. Crush washers are very soft copper.
Crush washers are still used today on modern vehicles where a rubber hose fits a cast iron caliper. The crush washer really needs a lot of torque on the hose fitting to do so. Some mechanics place the caliper in a vise and attach the hose with a line wrench and muscle it down. Then install both as a unit on the vehicle.
Note that the rear calipers do not have a rubber hose connected but instead have a flared steel line that matches the flare inside the caliper. Therefore, do not require a crush washer.
Thread Starter
Instructor
Joined: Sep 2013
Posts: 175
Likes: 3
From: Palmyra NY
Technically, it's a "Crush Washer". And technically it's a "One-time" use.
Brake calipers are cast iron. Where the hose threads into the unit is machined but still pretty rough. If a shiny steel hose fitting were to contact that ruff cast iron, a leak is sure to follow. That's where the crush washer makes a good seal and sacrifices its form. You are only supposed to use a crush washer once. But I have reused without issue.
Don't let a parts store sell you copper washers. It's not the same. Crush washers are very soft copper.
Crush washers are still used today on modern vehicles where a rubber hose fits a cast iron caliper. The crush washer really needs a lot of torque on the hose fitting to do so. Some mechanics place the caliper in a vise and attach the hose with a line wrench and muscle it down. Then install both as a unit on the vehicle.
Note that the rear calipers do not have a rubber hose connected but instead have a flared steel line that matches the flare inside the caliper. Therefore, do not require a crush washer.
Brake calipers are cast iron. Where the hose threads into the unit is machined but still pretty rough. If a shiny steel hose fitting were to contact that ruff cast iron, a leak is sure to follow. That's where the crush washer makes a good seal and sacrifices its form. You are only supposed to use a crush washer once. But I have reused without issue.
Don't let a parts store sell you copper washers. It's not the same. Crush washers are very soft copper.
Crush washers are still used today on modern vehicles where a rubber hose fits a cast iron caliper. The crush washer really needs a lot of torque on the hose fitting to do so. Some mechanics place the caliper in a vise and attach the hose with a line wrench and muscle it down. Then install both as a unit on the vehicle.
Note that the rear calipers do not have a rubber hose connected but instead have a flared steel line that matches the flare inside the caliper. Therefore, do not require a crush washer.
Thread Starter
Instructor
Joined: Sep 2013
Posts: 175
Likes: 3
From: Palmyra NY
Okay, I did some checking today. Unplugged the connector on the proportioning valve switch and the light goes off. There is a copper washer at the end of the rubber hoses. One thing I noticed and fixed was that the rubber seal on the bottom of the master cylinder didn't have the two cups pulled down. Drove car, light on but when applying the brakes the light will go off. I will be buying four new calipers for it in the spring (money really tight right now) and have them installed. My mechanic did mention that when he clamped off the front brake hoses the light goes out. Sometime freaky must have happened when I installed new pads.
Race Director
Joined: Mar 2017
Posts: 11,953
Likes: 4,510
From: Virginia
Okay, I did some checking today. Unplugged the connector on the proportioning valve switch and the light goes off. There is a copper washer at the end of the rubber hoses. One thing I noticed and fixed was that the rubber seal on the bottom of the master cylinder didn't have the two cups pulled down. Drove car, light on but when applying the brakes the light will go off. I will be buying four new calipers for it in the spring (money really tight right now) and have them installed. My mechanic did mention that when he clamped off the front brake hoses the light goes out. Sometime freaky must have happened when I installed new pads.
But the highlighted part is concerning. There is a tool for this, but still....