Very Soft Brake Pedal - Cannot Figure Out What's Wrong!!

**SeveredStar** · 10-05-2010

I have replaced the brake pads, calipers, rotors, and master cylinder on my '99 Grand Prix GTP. I have done other brake jobs in the past on other GM vehicles with no issues whatsoever. This time around though, I can not get the brake pedal to stiffen up once the car is turned on. I have bled the line numerous times with the aid of my helper, thinking maybe air was trapped in there somewhere, but the fluid is coming out fine with no bubbles. I was told that I may have to purchase an ABS scanner to reset the ABS? (My ABS light has not come on once during this process so I am uncertain that's the cause)The brake pedal is very firm when the car is off, and all parts are the correct ones and are working correctly (calipers are grasping, etc), but as soon as I start the car the pedal goes all the way to the floor and after pumping it a few times it still will not firm up. Am I missing something here? I am really lost as to what the issue is, and no one I know has any idea as to what is the problem. I've checked the line for internal leakage/bulging and that's not a problem either. If anyone has any suggestions/ideas as to what may be causing the extremely soft brake pedal, it would be appreciated. I am just hesitant to buy a pricey ABS scanner since no one rents them in my area and it may not be the solution to this problem. Thank you!!!!!

**matt5112** · 10-05-2010

brake boooosta?

Throw an impala one in there.

**BillBoost37** · 10-05-2010

Mechanic buddy once suggested this to me when I was at my wits end about a soft brake issue and had bled them to death already.

Take 4 pairs of vice grips and clamp all 4 wheel lines on the rubber hoses. Use a reasonable amount of force that will close the line, but not hurt it. Push the pedal with engine running, it should be solid. If it's not solid, look at MC or booster. Doubtful, but possible air in lines. If it is solid, release one vice grip at a time and test the pedal after each release. When the pedal goes soft again, you've found the wheel in which to look over.

**SeveredStar** · 10-05-2010

The car initially just needed new pads/rotors, and I ended up replacing the calipers after further inspection; after much bleeding I replaced the master cylinder thinking that was the cause of the soft pedal but it wasn't. Can a brake booster give out after replacement of the mc, calipers, etc? Seems highly unlikely that the booster would turn to crap after a simple brake job, I wasn't having any major issues beforehand, just felt it was maintenance time to change out the pads, etc.

**kjohnson** · 10-05-2010

If you cant figure out whats going on I'd give the booster a shot. i had an s10 that when the booster went out I could hardly stop the thing. on the other hand tho I could still get the brakes to firm up once I got em pumping. so im hesitant to say booster

**SeveredStar** · 10-06-2010

Is it normal for a booster to just give out when you replace pads/calipers/rotors/mc? It just doesn't make sense to me that it would just quit working like that. I get parts at cost so it's no problem, I just don't want to have to spend unnecessary amounts of money and time (like I did on the master cylinder, which I know now was fine beforehand and was not the cause of the soft pedal). Does anyone know of any good ABS Scanners? I heard Actron was a good brand. I think I may purchase one and scan the system, I heard you may have to reset the ABS on the Grand Prix. Is that a necessary step? It was mentioned in my Chilton's but not as a necessity. Thanks again everyone!

**kjohnson** · 10-06-2010

youll have to wait for someone else to chime in about the scanner. I dont know anything about them. I dought that you replacing the parts would cause that to go out like that but when my last one went out it was more like an o **** I all of a sudden dont have brakes

**OH4CompG** · 10-06-2010

Crazy question.... Are your brake bleeders on the calipers pointing up or down? If your bleeders are pointing down, you put the calipers on on the wrong sides and you will always have air in the lines and a soft pedal. Swap the left with the right, and visa versa so that the bleeders are pointing up and bleed the brakes.

**SeveredStar** · 10-07-2010

OH4CompG - Are you talking about the front or rear calipers? Front go sideways; For the rear - one bleeder is pointing up and one is pointing down. Switching them will still end up w/ one pointing up and one pointing down. I had never heard of that before - that they both had to be pointing up; is that something specific for GP? I know I purchased the correct calipers, so I am a bit puzzled. I had a neighbor over last night who works at a Chevy/GM Dealership, we ruled out the booster as being an issue but even he was at a a loss since there's no air in the lines (bled everything for about the 50th time!) and no leaks. Thanks to everyone for their advice so far, any additional comments/advice are appreciated as well, I'll take anything I can get!!!!

**TheOtherNick** · 10-07-2010

The bleeds need to be above the line going into the caliper. Air rises

**BillBoost37** · 10-07-2010

With a bleeder pointing down, the fluid is going in the hose and staight out the bottom, leaving all the air in the caliper.

If you tried what I suggested, you'd be done already. I'm putting $5 on your feeling like a dumbass when you actually look and realize you put the calipers on the wrong sides.

Anyone ever wonder why people ask for advice and then ignore it? Good thing I burn a lot of calories typing all day to waste my time.

**OH4CompG** · 10-07-2010

Originally Posted by SeveredStar

OH4CompG - Are you talking about the front or rear calipers? Front go sideways; For the rear - one bleeder is pointing up and one is pointing down. Switching them will still end up w/ one pointing up and one pointing down. I had never heard of that before - that they both had to be pointing up; is that something specific for GP? I know I purchased the correct calipers, so I am a bit puzzled. I had a neighbor over last night who works at a Chevy/GM Dealership, we ruled out the booster as being an issue but even he was at a a loss since there's no air in the lines (bled everything for about the 50th time!) and no leaks. Thanks to everyone for their advice so far, any additional comments/advice are appreciated as well, I'll take anything I can get!!!!

On the fronts, make sure both bleeders are above the brake line connection to the caliper. On the rears, if one is facing up and one is facing down, they sold you two of the same side calipers. There is supposed to be a left side and a right side caliper for this very reason. You have air in your lines and no amount of bleeding will get it out as long as you have the wrong caliper on the rear. FYI, this is not gp specific, this is every vehicle with a hydraulic brake system specific. Air rises.

**SeveredStar** · 10-07-2010

BillBoost - I started this thread on behalf of my boyfriend. A good look at my username shows that I'm a female, as does all of my previous posts regarding Air flow sensors, etc. I was just typing what I knew based on the information he kept on giving me and what he told me he did/didn't do. I thought I'd get more realistic answers if I asked them as if I was doing the work, b/c I think girls aren't taken seriously on car boards (no, scratch think, I KNOW!!!) I really don't appreciate being called a dumbass, I was just giving everyone the info he was giving me, don't kill the messenger

I called him today to ask him about the positions of the bleeders and that's what he told me and said he never heard of that making a difference before. It's my '99 grand prix he was repairing, he told me what he's done in the past and what he did w/ this car so far. We had gone to O Reillys together to get the correct parts and I knew that wasn't the issue, I figured it was just the car being fickle because everything than can go wrong on a car has on this particular one. I was trying to get him the info at various message boards while I was at work and he was working on my car at home. Trust me this has not been a picnic for either of us. Turns out we didn't bleed the mc or something like that. Im just glad I'll have my car back to drive instead of having to borrow one. So yeah, thanks to everyone again for their help. And, I'll go ahead and tell him about those bleeder lines needing to be pointing up but I think it's already fixed since everything seems to be working okay now. Seems being the keyword

Hopefully it is. Thanks everyone for your help.

Oh and one more thing Billboost,
"Anyone ever wonder why people ask for advice and then ignore it? Good thing I burn a lot of calories typing all day to waste my time."
Hey! Welcome to my world, that's what it's like being a chick telling a guy what may/may not be the problem with a car

**JDCMoney** · 10-07-2010

I had the same problem... I was bleeding in this order... right rear, left rear, right front, left front and Kept getting a hard pedal until I started it up... Under alldata it claims to bleed in this order...

Right Rear, Left Front, Left Rear, Right Front

I did it that way and I now have a nice stiff pedal....

Give that a try.