here is what i did according to my manual.

1. pump brakes until pedal is firm. hold pedal down in firm position.
2. start car, pedal should depress slightly. continue to hold pedal in this position
3. turn off car

when i turn off my car, my pedal goes to the floor (bc i have positive pressure pushing on it form myt foot.) the book siad it should go down after 30 seconds. mine did it imediately.

do i have a bad booster or just a vacumm leak?, my brakes seem to work but squeek at low speeds. any thoughts? i hav enever heard of one of these goign bad.

 

The booster is vacuum powered. You might want to replace the hose that goes from the engine to the booster, it have have small holes in it if its old. If not then you do probably need a new booster. Do you have to pump the brakes when the car is on and you are driving?

 

when i am driving i don thave to pump the brakes, but when i am at the stop light i can press them to the floor.

 

OK so no matter if the car is running or not the pedal will sink to the floor eventually correct? If so then its your M/C and not your booster I was having the same problem that they sunk to the floor no matter what and I replaced my M/C and its all good now. Oh but I woulod check the hose like he said and if anything check the check valve as well.

 

if the car is off and i dont turn it on, I can pump my brakes and get great pressure.

its only when i turn the car on and then turn it off that it goes to the floor, or when it is on.

 

It doesnt matter if you can pump them and get good pressure if you sit and hold your pedal down do they sink?? I was bleeding my brakes and they bled fine but the M/C was still bad. I could pump them and get pressure its just when your sitting there with constant pressure is when it would sink.

 

Its probably your MC. Sounds like the seal inside is slowly breaking down. Mine did the same thing, it would work fine when the car was cold but if I used the car in the heat for a while the pedal would sink to the floor when I stopped.

 

I think my brake booster is bad(only thing left I haven't replaced). When I'm driving, I have to pump the brakes to get them to work. First pump goes to the floor, second half way, then 3rd pump as to where it should be. I followed the tests in the helms manual:

"Start the engine with the pdel depressed. If the pedal sinks slightly, the vacuum booster is working. If the pedal height does not vary, the booster or check valve is faulty"

I did this and the pedal did not move. There is also another test in the manual:

"Depress the brake pedal with the engine running, then stop the engine. If the pedal height does not vary while depressed for 30 seconds, the vacuum booster is ok. If the pedal rises, the booster is faulty."

I did that and my pedal came up right away Time for a new booster?


Modified by miataguy at 2:18 PM 9/1/2003