My 79 fleetwood brougham has 4 wheel disc brakes from what i understand they (cadillac) did this for the 78 and 79 models. I had new brakes, calipers put on and then proceeded to bleed the brake lines. For the first week or so the brakes reacted fine, then recently when i engage the brakes the brake pedal goes to the floor and the brake light comes on briefly then goes out when i let up off the brake pedal. The owner before me explained to me that the different mechanics she took the car to said that the car had some kind of floating brake mechanism which to this point no body has been able to address. If anyone out there has any info that can validate my problem with your talents will be more than :worship:appreciated. My caddy has a 5.7 engine.

Are you loosing any brake fluid?

My 79 fleetwood brougham has 4 wheel disc brakes from what i understand they (cadillac) did this for the 78 and 79 models. I had new brakes, calipers put on and then proceeded to bleed the brake lines. For the first week or so the brakes reacted fine, then recently when i engage the brakes the brake pedal goes to the floor and the brake light comes on briefly then goes out when i let up off the brake pedal. The owner before me explained to me that the different mechanics she took the car to said that the car had some kind of floating brake mechanism which to this point no body has been able to address. If anyone out there has any info that can validate my problem with your talents will be more than :worship:appreciated. My caddy has a 5.7 engine.

First off, I have no firsthand experience with your '79 brakes.

Floating brakes generally means the calipers are free to move laterally. The bolts (pins is a better description) that position the calipers allow the caliper, and as a result, the pads, to move just slightly inboard or outboard when brake pressure is applied. These pins should be free of corrosion and lightly coated with high temp grease and the caliper should be free to move.

Your brake light is "probably" associated with the fluid level in the master cylinder. And certainly check for fluid leaks.

As already advised, check the fluid level. If the level in the MC goes too low (because of a leak, or when you're bleeding the fluid) you'll have to pull the MC and bench bleed it. Not hard, but while it's off, you might as well replace it.

By what you described, I would suspect the MC itself. It's easy to fix and not very expensive. Given the age of your vehicle, unless you know the MC is good (i.e. you have service records for it) I'd replace it.

Also, inspect all your brake lines. If they are dried out and/or cracked, get rid of them. This is another easy job.

Your car has normal disc brakes, as found in every other car out there, save for the C3 Corvettes (68-82). On those, GM used a floating piston that relied on a seal to keep the fluid in and the air out. While this setup provides excellent braking capability, it is very troublesome. Items as simple as inappropriate rotor runout, can introduce air into the system. Not fun. This problem can be addressed by rebuilding the calipers with O-ringed pistons. But you really don't have to worry about any of this.

Just check and/or replace your MC and brake lines. Then, you should be good to go.

I just want to say thanks to those of you who responded to my problem. You've been a big help in narrowing down what solution I need to correct my brake situation.

I had a 1979 Seville with the 4-wheel disc brakes that had the same problem. It ended up needing a new proportioning valve and master cylinder. Also, the dealership recommended that I use the emergency brake everytime I park the car, regardless of whether or not I am on an incline. They said the reason was because it adjusted the rear discs each time ... not sure of that but I never experienced the problem again after I started using the e-brake. Hope your problem is not as bad as mine was. If I remember correctly (I had the car in the early 90's for about 3 years) the proportioning valve and labor was not cheap from the dealership. Good Luck!

I had a 1979 Seville with the 4-wheel disc brakes that had the same problem. It ended up needing a new proportioning valve and master cylinder. Also, the dealership recommended that I use the emergency brake everytime I park the car, regardless of whether or not I am on an incline. They said the reason was because it adjusted the rear discs each time ... not sure of that but I never experienced the problem again after I started using the e-brake. Hope your problem is not as bad as mine was. If I remember correctly (I had the car in the early 90's for about 3 years) the proportioning valve and labor was not cheap from the dealership. Good Luck!
Setting your parking brake, everytime you park your car, is an excellent idea. This is true whether you have an automatic or a stick. It's the old "use it or lose it principal." Using the parking brake keeps the brake itself adjusted and the cables stick free.

Also, if you're not using your parking brake, you're relying on your automatic transmission to hold the car in place. The mechanism that does this is little more than a tab that at times, really can give out. Doesn't happen often. But wouldn't it be nice to know your parking brake is holding the car in place, as well?