brake pedal jumps when applied

[tipatalon]

hi , its my first post and glad to see that there's other fans of the grand prix. i'm in quebec so sorry for my english! ok, i have a 1997 grand prix se 3.1L and today when i applied the brakes, the pedal started to jump hardly (no its not the abs) like if there were snow in my rims. and more the car slows down , more the pedal gets softer. i don't know if i described it ok, what do you think it could be? thanks

[csssaint12]

Do I understand you correctly that when you keep applying pressure to your brakes that it gets softer and goes down to the floor?

[98GPGT2D]

A 97, brake vibration, soft pedal. Im inclined to say 3 things here. 1, bad/warped rotors. 2. With the age of the car comes rotten brake lines and loss of fluid. 3. Possibility of a brake booster/master cylinder issue.



Jay

[tipatalon]

A 97, brake vibration, soft pedal. Im inclined to say 3 things here. 1, bad/warped rotors. 2. With the age of the car comes rotten brake lines and loss of fluid. 3. Possibility of a brake booster/master cylinder issue.



Jay

yeah that could be a rotor, i've seen the right rear rotor rusted a bit, will check this first thanks

[98GPGT2D]

the only way you are going to be able to accurately check for a rotor issue is to have a shop (or yourself, if your mechanicly inclined) do a runout check with a dial indicator. A visual inspection will tell you nothing, other than a ware ridge on the surface from pad contact, and maybe heat spotting or checking.

Jay

[subziro34]

I have similar problems with gas pedal does anyone know if a faulty EGR valve might also be the cause of my gas pedal jumping after I shut of my "Betsy" . I was told that I need and EGR valve and ISC motor to cure the Service light and the slight gas smell after shut off. I am replacing the EGR this weekend and then will see what happens before I replace the $$ ISC motor. I just want to know the gas pedal thing....it freaks me out .Also every now and then when I put ole "Betsy" in park...she idles high...could the egr and/or isc motor have any effect on this? Btw I solve my problems with brakes after getting wagner brakes from local store here at my place.

[real diehl]

Is it doing it in snow? Please don't tell me your car is just going into anti-lock

[tipatalon]

Is it doing it in snow? Please don't tell me your car is just going into anti-lock

please read my first post

[tipatalon]

the only way you are going to be able to accurately check for a rotor issue is to have a shop (or yourself, if your mechanicly inclined) do a runout check with a dial indicator. A visual inspection will tell you nothing, other than a ware ridge on the surface from pad contact, and maybe heat spotting or checking.

Jay

thanks will check that, if it were the front i would feel it in the steering wheel?

[98GPGT2D]

thanks will check that, if it were the front i would feel it in the steering wheel?

Yes and no, if its not too bad, no you wont. If it's really bad, yes, your steering wheel may "thump" or have a shimmy when the brakes are applied.