midweekwarrior

i have a squishy brake pedal and a vaccum hiss from under the driver side dash. Power brake booster gone bad? ..that's my opinion

92ragtop

Since the booster is a PITA to change, you'd want to first ensure that it's not a vac hose that has broken, split or let go. Also, you can use a dental mirror to check the booster for obvious cracks.

NASCAR314

Try flushing the brake fluid by bleeding at least 1 quart of new fluid thru. Best method is a person inside pressing the pedal while someone else cracks open the bleeder at the wheel (RR,LR,RF,LF) don't let the master cylinder run out of fluid. Get clean fluid out of the first corner before proceeding to the next.

If booster was cracked, you would have to stand on the brake pedal to get the car to stop. But, as noted earlier, you can inspect it for cracks. They are plastic, and crack near the exhaust manifold side.

If brake pedal goes all the way to the floor, it may be the master cylinder is leaking internally. Or, massive amounts of air in brake lines.

jhammons01

^^Yes, a squishy pedal would not be brake booster.....

midweekwarrior

This couldn't be caused by a bad diaphragm inside the booster?

More information:

As far as i can tell the booster has no cracks, and no fluid leaks from the master or lines since, my master is topped off still.

Inside underneath the dash (where the brake pedal enters the firewall) is where i hear the most "hiss" and there is a rubber gaurd of sorts (not sure what it is) that covers the area. Im not sure if that gaurd has to be attached to something or not, but it is loose on my car.

The valve, where the vaccum takeoff connects from the engine, I can wiggle with my fingers (pretty sure if i tugged hard enough i could pop it out).

The level of "squishy" increases or decreases with the amount of time i drive the car or how cold it is outside. When it was snowing the other day i had to almost use both feet to get it to stop, and no i wasn't sliding.

This issue also happened overnight practically, if i remember right, i might have locked the brakes up or something.

JackDidley

Maybe squishy is not the right term ????? If the pedal is hard, like you said you needed 2 feet to press it, you have a bad booster. Its not hard to replace. Do a search for the best way.

jhammons01

Ahhh, check the ABS module....

Many members, and I do not know how, have done something that resets the ABS module and years of chasing poor brake performance disappears with a "click"

Sorry for not having more info on the ABS reset procedure, but think of it this way, your ABS is fighting you as it thinks one or more wheels may be sliding...so it pushes back against your foot as it is designed to do.

midweekwarrior

the pedal isn't hard...

it is squishy, with very little resistance, for the top 1/3rd or so of the travel and the resistance increases and you have a "hiss" noise. As you increase your foot pressure on the pedal the pedal becomes harder and begins to feel like a normal brake pedal