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Just to settle this once and for all, I have a couple questions about the brake warning light for a 68 std.

First off, does it have any relation to the parking brake or is it strictly a warning light for brake system failures.

Secondly, I have heard when it was illuminated one portion of the brakes were bloked off. I ask because mine is on and I bled the brakes with no problem after replacing the leaky wheel cylinders in the rear which makes no sense if a portion were blocked off. Furthermore, the service manual says it will stay on after repair and bleeding. If it blocked off one of the brake systems, wouldn't they be impossible to bleed blocked off.
 

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I'm pretty sure there's a thread on this in the archives somewhere - or maybe just farther down in this group - anyway - the brake light you are talking about has absolutely nothing to do with the emergency brake (unless it's the emergency brake warning light on the lower part of the dash - this one flashes when the emergency brake handle isn't pushed all the way in - NOT the one you are talking about, I think).

Anyway, here, in a nutshell, is what you have going on...

There is a valve in the mess-o-stuff near the proportioning valve near the master cylinder (mounted to the inner fender shell on the driver's side, near the hood hinge). If you look at that, you'll see a cute little switch, identified because it will have a wire connected to it.

If you were to take that switch out and look at it, you would see a little brass button coming out the bottom - that sits in what I like to think of as a "V" in the rod below it inside the valve housing it screws into. Actually, it is a piston with a "V" notch in the middle of it's shaft (kinda like a dumbell with a "V" slot cut in the center of the handle). That "V" is on a valve that can move forward and backward. It sits in a fluid-tight chamber in the valve - on one side of it, it is exposed to fluid pressure for the front brakes, the other side of the "V" bar is exposed to fluid pressure for the back brakes.

When this piston is in the middle, the post on the bottom of the electrical switch is in the deepest part of the "V", and the switch is open, so that the light on the dash is OFF.

If, as I am sure is the case with your cat, the pressure on one side of the valve (either in the front circuit or the rear one) is less than the other - - - say, due to a leak in the brake system - or, interestingly enough, due to the mechanic bleeding one set of the brakes *wink* - - - then the dumbell/piston slides toward the side of the circuit with the lower pressure - - this causes the "V" to move, and push the post on the switch upward, closing the circuit and making the brake light inside the car go on.

Viola' - one frustrated cougar owner!!!

I got around my problem by unhooking the switch *LOL* - but - I intend to get around to fixing it next time I have to do any brake work.

Check out the archives - if you bleed the front and rear brakes to try to center the piston - it won't work - because the piston will always move to the open side of the circuit. You have to somehow "hold" the piston in the middle until all the bleeding is done - there are some recommendations in the archive somewhere about doing that.

Damn...now my fingers are tired - but - I do have an amazing sense of increased self-worth having written this dissertation, and in the process of doing so, helped out a fellow Coug owner. DAMN, I'm GOOD - Now...I'll be floating around all day on a cloud of self-importance, until my daughter asks me something I can't answer *sigh*

Hey, I'm easily impressed with myself - what can I say? ;)
 

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Ford has an answer to this. When you finish bleeding the lines, you need to "re-center" the proportioning valve. To do this you go the other side from the last side you bled. That is if you bled the rear last, you re-center on the front, and vice-versus.

You might need 2 people to do this. You have one person in the car with the ignition switch set to ON (not running). You then have them slowly press on the brake pedal while you open a bleed screw on one of the calipers/cylinders. When the brake light goes out, you tighten the bleed screw. I'm just repeating what I read. I haven't tried it yet, but I'll give it a try next week when I get the brakes back on.
 
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