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96Buick LeSabre 3.8L Lack of Brake Pressure

In Oct. my wife took the car 40 miles from home, lost the brakes, and limped into a gas station. The guy there gave her a bottle of brake fluid and some stop leak. He suggested equal amounts of both and limp back home. She drove back and went to the machanic in town. He wanted $365 to replace all of the brake lines. He said there may be brake pressure problems and he will address them later. Recently I loaned my son the car so that he could deliver newspapers. After 2 weeks we needed new front brakes. I had brake pressure problems. If the brake pedal did not feel spongy then the brakes felt inconsistent-sometimes high and sometimes down to the floor. There was a sticky passenger front caliper that was repaced. The brakes were bleed and are still spongy and inconsistent. I noticed that the reservoir cap is not good. Could the cap be the cause of the sponginess? There are no leaks around the master cylinder and there are no leaks. Should I replace the master cylinder?

There is no stop-leak product for a brake system. This is a safety system and if there’s a problem with the system it must be repaired.

But from what you describe, the brake master cylinder would be the first suspect.


I’m thinking this second mechanic believes the so-called “stop leak” the first mechanic put in was actually not designed for brake use, and now, since this substance is in the lines, the best sol’n is to replace the lines before it damages the rest of the system. There could be merit in that logic I suppose.

I expect the sponginess is the result of the brake fluid going low the first time. Air got into the system and remains. The cap on top of the fluid resevoir should be fixed, but it isn’t what is causign the sponginess. But it might contribute to dirt getting into the fluid, which could make the brakes fail. I guess if this were my car, I’d ask the mechanic to fix any visible leaks, check the master cylinder & replace it if it is not working correctly, then flush out all the existing fluid, replace with new, and bleed the system. Then I’d monitor the performance to make sure there weren’t any remaining problems.