1990 Oldsmobile Cutlass Brakes

Hello and thanks for donating

first off, check to ensure you have brake fluid left in the brake master cylinder resevoir.

Since you do have brake fluid, lets make certain you have bled the brakes properly. You need to bleed the right rear brake first and when your helper is pushing on the brake pedal he/she needs to tell you when the pedal hits the floor when you open the bleeder valve so you can close the valve before they lift their foot. And when they pump the pedal back up they need to use slow long strokes. Left rear second, right front third and left front last. You should by now have some pedal feel. So rebleed in the correct sequence.
If you can pump up a fairly good pedal and hold light pressure for several minutes the master cylinder is probably ok. However if you can pump up a fairly good pedal and if you hold light pressure and the pedal slowly goes down you either have a leak or your master cylinder is bad. If you repeatedly bleed and get NO air bubbles in the bleed line but you have a very soft pedal, you have too much movement somewhere. The standard method to find the movement is to run one rear wheel brake adjuster up tight as you can to lock up that wheel and check the pedal again. Then do the other rear wheel the same leaving the first locked up. If you still have a very soft pedal leave both rear wheels locked up and take a bright light up to a caliper and look closely at the relation of the disk to the caliper and have someone pump the brake pedal while you watch for ANY movement. If you see movement then probably one piston is stuck and not moving and the other is pushing the disk over to meet the other brake pad/piston. Check both sides. A stuck caliper piston will make the other piston displace more fluid than the master can supply in one stroke. Don't skip any of this, every step is very important.

Well, one of the circuits in the master cylinder may have failed -- which would mean that the master cylinder is toast. If the pedal travels a long way before the brakes start to work, that might indicate a problem with one circuit (front or rear) in the master cylinder.

There could be a problem with the flexible brakes lines near the wheels. As the brake lines age they swell internally, this reducing the flow of brake fluid until the brakes start to grab. Sometimes this will start the brakes binding even when your foot its off the brake pedal. When you use the brake pedal, fluid is forced through under pressure, and the brakes stay on when the pedal is released because the fluid is very slow to leak back up the blocked flexible line.

Try this test - remove each flexible line from the brake hub itself (one at a time) and see if fluid dribbles through the line (take the cap off the fluid bottle up front to make sure it can flow easily).

If there is only a tiny drip or no flow at all, try removing that flexible segment and see if the fluid then dribbles out the metal body line. If the flow is good, then the flexile line is bad and must be replaced. They are not too expensive and should be replaced every ten years or so anyway.