Dash brake light
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Junior User
Joined: Sep 2003
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Dash brake light
My warning light seems to be coming on a lot lately. I've bled the brakes and when i do the rear left brake always seems to have air in it. This gets rid of the brake light but then it comes back a week or so later.
Any ideas? I'm not losing fluid. How can air be getting into the system?
Darryl
80 Bronco
Any ideas? I'm not losing fluid. How can air be getting into the system?
Darryl
80 Bronco
Lead Driver
Joined: Sep 2002
Posts: 9,182
Likes: 12
From: Gateway to the West
If air is getting IN, fluid has got to be getting OUT. Otherwise you would have no problems. I would take that left rear drum off and make absolutely certain that wheel cylinder isn't seeping even a little bit. If thats not it, follow the steel line back to the splitter on the rear axle. If the only air is in the left rear the problem has almost got to be somwhere in that stretch of the system. Since the left rear is the furthest point from the master cylinder in the hydraulic system, its unlikely the problem is anwhere else or the air would be present at wheels closer to the master cylinder. Simple physics, the air will travel the path of least resistance.
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Junior User
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The side I'm talking about is the driver side rear.
I do notice some paint missing on the brake booster where the master cylinder attaches to it. The paint is bubbled as if you used paint remover and I know brake fluid takes off the paint. I wonder if the master cylinder has a small leak. Problem is the fluid is at the correct level.
This all started when I took the front calipers off and had to push the piston in on the caliper. Before it was working fine.
I do notice some paint missing on the brake booster where the master cylinder attaches to it. The paint is bubbled as if you used paint remover and I know brake fluid takes off the paint. I wonder if the master cylinder has a small leak. Problem is the fluid is at the correct level.
This all started when I took the front calipers off and had to push the piston in on the caliper. Before it was working fine.
Post Fiend
Joined: Nov 2002
Posts: 9,987
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From: Memphis, TN
The dash light doesn't monitor fluid level or air - it shows the position of the proportioning valve mounted inside the frame rail directly below the booster. By working the calipers like you did, you put the switch inside the valve off center. The Haynes manual tells how to recenter it by bleeding the brakes. That's the ONLY thing that will correct your problem.
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Junior User
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Makes sense but I bled the brakes and it didn't do anything. Well actually it did make the light go away and the brakes weren't as spongy but in less than a week the light was on and they were spongy again.
I replaed the master cylinder and so far everything is working pretty good.
Very strange.
I replaed the master cylinder and so far everything is working pretty good.
Very strange.
