No pedal at all with power disc brakes front and rear could be caused by one or more of the following conditions:
A defective master cylinder.
Sounds like a broken seal preventing any pressure from being acheived.
Air in system.
Believe it or not sometimes when you think you've removed all the air, you haven't! Go back and check to be sure all bleeder screws in the system are oriented properly to allow all air to escape. Be particularly careful that the caliper bleeder screws are pointed up allowing all the air to escape when bleeding.
If you are using a low drag or metric GM caliper without the correct quick take up master cylinder you will never get a pedal. In 1982 GM started using the smaller metric caliper because it's design retracted the caliper piston up to .125" ( a regular caliper retracts 2-4 thousandth's of an inch). This is a lot and without the correct quick take up master to move the caliper piston sufficiently your brake pedal will be extremely spongy. The metric low drag caliper can be identified by a chamfered leading edge of the square cut groove for the piston seal.
Rear caliper problem
If you are using Cadillac ElDorado rear calipers there are some important things you should know. One of the biggest advantages of a disc brake system is the fool proof self adjuster. Not so with this rear GM system. The rear calipers adjust off the parking brake. The parking brake is incorporated into the caliper. You must set the parking brake every time you park the car.The rear caliper pitons utilize a one way clutch inside the caliper piston. When the parking brake is applied the clutch senses when there is .030" or more clearence between the friction material and the rotor on the inboard side. When there is more than .030" the clutch turns inside the piston adjusting it out keeping the rear brakes adjusted. If you do not set your parking brake every time you will start to lose brake pedal (low and spongy) and the adjuster mechanism will not work any longer. Also: never use rebuilt calipers on the rear because the rebuilders use the old pistons and the pistons were the reason the caliper failed in the first place.
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