OK, this is driving me nuts. The brake light comes on and stays on. I've blead the brakes 3 or 4 times and each time the light goes out. I park the car on level ground for a couple of days and when I start it the light is back on. If I park the car nose up on a grade for a few hours the light goes off.

I suspect it's the metering valve on the frame below the master cylinder. Does anyone have any better ideas? Does anyone have a replacement? I've checked Ground Up and Year One catalogs but neither lists them. Does anyone rebuild them?

TIA

Have you checked the brake light switch under the pedal? I had a problem with my brake lights staying on, and the switch was loose. Tightened it up and the problem went away.

Chris

Have you tried pulling the connector off the valve to prove it's the valve causing it? The light should go out.

Is that the same light on the dash, that lights when the parking brake is on with the car running? That switch could cause the light to go on and off if it's loose.

If I park the car nose up on a grade for a few hours the light goes off.

I suspect this combined with RedSS's suggestion is your problem. I think gravity is helping pull the brake pedal "up" when you park on a hill. Put the car on level ground so that the light is on and then pull up on the brake pedal to see if the light turns off. Could be the return spring is broken/weak.

Have you tried pulling the connector off the valve to prove it's the valve causing it? The light should go out.

Yes John, when I pull the wire the light goes out (that's how I drive it between bleedings).

I also know that it's not the pedal switch. On the chevelles that I've looked at the light is not as bright with the pedal depressed as it is when the fluid switch is offset. I replaced the pedal swich a couple of years ago an I know it is adjusted properly. This problem has developed more recently.

That was a good idea though, thanks.

Any more?

Don't know of a good way to determine if the switch is rocking towards the rears or the fronts. It will rocker if the pressure is low on either one. Thought Ground Up repaired the later (71/72) combo valves. Maybe they also work on your year. Maybe True Connections has a used one.

Year One has them. They are high priced. This place rebuilds them. They advertise in Hemmings. http://www.whitepost.com/brake.html

Are your brakes working well, just the light is the problem? I had trouble after replacing the master cyl a couple years ago, but along with the light on the brakes didn't work well. Took a lot of pedal effort to stop. Bled the brakes 4 or 5 times. Finally wet the pavement in the driveway and stomped the brakes while rolling. The rears wouldn't lock up. I thought it was the master cyl but turned out to be air still in the lines (yes I bench bled the MC). After getting a special bleeder wrench and a thorough bleeding of the rear brakes, problem gone.

I agree with Von. There's an air bubble hiding in the lines somewhere that needs to be bled out. You might try bleeding them in this manner-- Use a piece of clear hose attached to the bleeder so you can see any bubbles, and only open the bleeder 1/4 to 1/2 turn. One person in the car, one by the wheel (start with the right rear). Open the bleeder and say "Open!". Then have the person in the car slowly push the pedal down until it bottoms, then that person says "Down!". Close the bleeder, and say to the person in the car "Up!". The in-car person then lets the brake pedal up and says "OK!". Do this 3 or 4 times or until you no longer see any bubbles in the line. Then check the level of the fluid in the master cylinder & top it up. Go to the left rear, then the right front, then the left front. If you still have a problem, then the valve is probably bad. I just replaced my booster & master cylinder and I wore Angee's leg out getting all of the air purged. :D

BillL

OK, thanks. I'll try it again. (the car is getting dizzy though going up and down on the lift)

In addition to the last post, bleed the brakes starting from the farthest cylinder to the closest(rr, lr, rf, lf). Also, if working alone, you can use a longer tube on the brake bleeder, with the end submerged in brake fluid. Just open the bleeder, and pump the brakes. Just keep an eye on the fluid level in the master cylinder. Also, a vacuum pump can be used to suck the brake fluid out from the bleeders, and they make pressure bleeders that go over the master cylinder. If you haven't had your brake system open prior to this problem starting, I would suspect component problems rather than air. Don't drive the car with this problem. Most metering valve systems will close off the ports to the leaking system of the car. So if you blow a rear wheel cylinder, the valve in the block will move under spring pressure and block the port to the rear wheels, to prevent any further fluid loss.
You mentioned that parking on an incline will shut the light off. THAT sounds like air. I would be more suspicious of the fronts. It seems the air could travel to the calipers and hide there, on level pavement, the air could slowly creep into the metering valve, where it would be compressed easier, and allowing the piston in the vavle to travel and block(or partially block) the fluid to your front brakes. That is especially bad, since your fronts do most of the work. I would not drive the car until the problem is resolved.
Metering blocks are very simple(as the rest of the hydraulic braking system), comprised of a porting piston, seals, 1 or two springs and the body. The piston rarely(almost never, normally) travels, so wear and scores don't happen. As long as the system has had fluid in it, the seals should be okay.
If for some reason, it is the metering valve, I think you would be okay to get a junkyard replacement, as long as the brake system hasn't been compromised. Brake fluid is hydroscopic(attracts water/moisture).

Did you trying playing around with the parking brake pedal? My 70 has this problem, if I disengage the parking brake, the light will stay on since the switch on the pedal works off of ground and it's not grounding out to make the light go off. I need to adjust the tension on it, but I usually just give it a little pull upwards with my foot and it goes off.

Also, a vacuum pump can be used to suck the brake fluid out from the bleeders, and they make pressure bleeders that go over the master cylinder.

I've had poor luck with vacuum bleeders on drum brakes. The problem is that the vacuum contracts the seals in the wheel cylinders and they will draw in air. Pressure bleeding works best since the pressure expands the cup seals so that they do their job. :thumbsup:
BillL