Weird Brake Booster Problem (87)

Hey, on my '87 TC the brake booster went out a while ago. It was unusually soft when I got the car and then one day the brakes all but died. When I put them to the floor I had almost no resistance and barely enough braking power to keep the car still. So I disconnected it and plugged the vaccuum line. Worked fine. Well this weekend I reconnected it so that I could try to test exactly what was wrong with it before I decided to replace it. Low and behold, its exactly as it was before the brakes went out. Very very very soft. It also makes kind of a whoosh sound (the pedal not from the engine compartment) when I depress the brakes. It stops fine but I'm worried about it going out again. Any ideas? Should I replace the booster or does it sound like something else? Also, anyone know how hard it is to replace a brake booster, it seems like its easy enough to do at home, but I'd like to hear someone's opinion on it. Thanks.

-Joe

I had a few big-ass Fords that made that woosh sound too. It turns out, Ford put a air piston thing on the pedal in an early attempt at anti-lock braking.
The air bellow's or chamber, or whatever they called it back then stopped the driver from quickly depressing the pedal.

The booster is assisting you depressing the pedal by pulling the pedal down, as you're pushing it... So yes, it should feel much "softer" with the booster connected.

The fact that you can get the pedal to go all the way to the floor has nothing to do with the booster, that's a Master Cylinder problem.

Two things kill a booster.
One: Rubber deteriorates and cracks. This causes engine vacuum to bleed when you press the brake pedal. Vacuum leaking sound may or may not be audible. Engine idle is severely effected.
Two: Master Cylinder end seal leaks into booster causing the booster chambers to fill with fluid, poor booster performance, and erratic operation.

Master Cylinder plunger cups (rubbers) loose their edge and their ability to hold tight to the bore of the cylinder, fluid bypasses the cups, braking effectivity fades, pedal travels abnormally downward.

So what I'm getting out of this is I might want to go ahead and do a replacement on the master cylender instead of the booster. I dont think there is a vaccuum leak in it because it idles fine when depressed.

You may have to replace both, if the mainseal in the Master Cyl. was leaking into the booster. I've seen some homebaked mechanics simply flush the fluid from the booster, clean it out, dry the inside throughly with compressed air and good 'ol sunshine, and reinstall the booster. You'll definately have to remove the booster to make that determination, cause you can't really tell what's in there, or not, from an installed position.