View Full Version : '00 GA GT Brake Problems.....
06-10-2012, 02:39 PM
This is my first post here, and I want to say thank you in advance for any help y'all are willing to give.
About my car:
2000 GA GT, 48K miles.
Calipers and rotors are original, as is MC, booster, lines, hoses.
Brakes were getting thin, so I replaced all pads and hardware on all 4 corners.
Here's what happened:
Used a big C-Clamp to push piston back into calipers.
Pulled rotors, scuffed up surfaces with 120 grit to give a good bite.
Replaced all pads/hardware.
Noticed there was too much fluid in reservoir after doing this; figured the Jiffy-Lube guys must've topped it off as the level went down with pad wear.
Jump in the car, brake pedal super soft and spongy. Dang.
Never cracked the system open, but decided to bleed anyway. Got some big air bubbles in the front, and some fizzy bubbles in the rear. Drove a few miles to heat everything up, then parked it 2 days to let the fizz settle.
Re-bleed. Got some air out. 1.5 quarts through just to be safe, and now the pedal is back up where it should be, but still much softer pedal than before!
After driving about 100 miles, checked the rotors.
All my scuff marks were worn nice and shiny in the rear, but only half of the rotor surface on the front brakes was worn shiny (the outer half, like a ring around the rotor).
Pulled front calipers, and pads seem to have wear only on the outer half as well.
Before, the car had a nice rock hard pedal with little travel, and braked nice and straight. No shake, pulsing, shimmy, or other signs of warped or sticking parts.
Now, the car has a softer pedal, a slightly longer travel, and still brakes nice and straight. No shake, pulsing, shimmy, or other signs of warped or sticking parts.
No leaks around MC or booster.
Hoses are all in top notch shape, no leaks or seeping anywhere around any hard lines.
Brakes were properly bled, and I am confident there's no air left in the system (not my first brake rodeo)
All caliper bores are dry (no leaks).
W.....T.....F is going on here?
Did I push the pistons too far back and now my front calipers are failing to travel as they should in the front?
I suppose I could just throw new calipers at it, but I'd rather get to the bottom of this.
The suspicious thing is the sudden presence of air in the system after just replacing the pads. That's gotta count for something; coupled with the front pads not engaging the rotors completely, I suspect this is where my problem lies.
Thanks to all who respond; I could really use some input.
06-10-2012, 04:08 PM
You blew a seal somewhere.
Did you take the cap off the master cylinder before compressing the caliper pistons?
06-10-2012, 04:20 PM
You blew a seal somewhere....
It had to be at the zoo...he doesnt live on the coast.
06-10-2012, 05:27 PM
LMAO. !!! Sorry back on topic !!!
06-10-2012, 05:31 PM
Sounds like pistons are not straight if your only getting wear on the outside of the pads . Is it on both wheels ?
06-10-2012, 05:32 PM
The most common problem for the soft pedal after the work you have done is a damaged master cylinder seal...this typically happens when you have to pump the pedal to get the pedel back up and the caliper pistons seated on the pads....normally, this means the pedal is pushed farther into the Bore and the master cylinder seal gets damaged from the crude in the cylinder from lack of fluid changes. First, You also should check to make sure all the slides on each caliper are free and not binding. But if he system is bled correctly most times a spongy pedel is a leaking master cylinder
06-10-2012, 06:27 PM
Yeah, you probably should have taken the cap off the M/C before pushing the pistons back in, and maybe even bleeding new fluid through them first would have been a good idea.
As for the pad wear and the wear pattern on the rotors. Your rotors are probably worn uneven. First, you don't need to scuff them with sandpaper when putting new pads on. In fact I don't recommend it. It's not needed to break in new pads. Second, 48k miles is a LOT of miles on a set of stock rotors that have never been resurfaced. Stock discs and pads usually don't last that long, and a lot of people have had issues with stock rotors warping. I always tell people to get the rotors resurfaced on at least every other set of brake pads, so that you have a fresh and flat surface for the new pads to bed in on. Otherwise you are just going to mess up a new set of pads and wear them down faster. Also I don't recommend turning stock rotors more than once because they get too thin and warp easier. You probably need new rotors. Maybe an new M/C now too. But make sure the caliper pins are well lubed up first, as mentioned above... although that shouldn't cause a spongy pedal.
06-12-2012, 09:58 AM
It had to be at the zoo...he doesnt live on the coast.
The mechanic tells him it'll take a while to figure out what's wrong and to come back later.
So the penguin decides to walk around town and gets himself an ice cream cone.
However penguins don't have thumbs, so the poor fellow gets ice cream all over himself,
When he returns to the mechanic, the mechanic looks at him and says, "Looks like you blew a seal."
To which the penguin replies, "No, that's just ice cream."
06-13-2012, 11:21 PM
Thanks for all the responses.
I'm "feeling" like it must be the MC, if for no other reason than the fact that both front calipers are performing equally (albeit poorly).
The brake fluid had not been flushed prior to my work on this car, so that's 10 year old fluid that did indeed look quite black when I bled the system.
The caliper pins are indeed well greased, I made sure of that when I slapped on new hardware, and I don't think the rotors are warped or worn unevenly, as the old pads had a nice level cut to them, and there's no warping on the rotors. I didn't bother to check the runout since they were performing so well before; perhaps I'll slap a gauge on a see what I get.
Lowest price for a new MC is around $68. WTF! Guess I need to find a rebuild kit somewhere.......
And the "Zoo" in my screen name refers to Mizzou, or Univ of Missouri :)
Any more suggestions, I'd love to hear.
06-14-2012, 04:12 PM
$68 is expensive?
06-14-2012, 06:10 PM
....and never sand a rotor..brakes operate on clamping force, not friction. The smoother ur rotors are the longer your pads will last.
06-17-2012, 02:20 PM
$68 is expensive?
If I knew for sure, 100% that the MC was at fault, then no. Since I'm more or less going to start throwing parts at the problem (albeit with solid input from the forums, thank you again!), then yeah, $68 is a lot to throw down on a part that "may" fix it. If I can find a rebuild kit and save some cash, I'd feel better.
Please understand I am not discounting or second-guessing anyone's advice; I'm just a tad cynical when it comes to my own good luck and fixing cars :D
I did find a rebuild kit for the MC; $16 before shipping.
As for the rotors, I've been doing that for years to break the glaze when changing pads/shoes. If the rotors or drums are decent enough not to warrant turning, I'll scuff the surfaces. It's not as terrible as it sounds. I've had back luck *not* scuffing the surface, but that's just me. We all have our little routines.
06-17-2012, 06:13 PM
If at a stop, engine at idle, if you press down on the pedal and it continues to go to the floor.......you have one of 2 possible issues....air in the lines and or a leaking master cylinder. That it. So..are you sure you have all the air out including the abs module? . If yes, then the master cylinder is bad. What is happening is the seals are bad so as you put pressure on the pedal fluid is leaking past the rubber seals in the master cylinder bore...the brakes work sorta but the pedal drops. When you bleed the brakes and have not kept up with fluid changes you should not push to far on the pedal..like to the floor....as the gunk in the cylinder can wreck the seals. If you do replace the master cylinder you must follow the correct proceedure to remove the air in the line before the abs module or you will have the same problem all over again
05-23-2013, 02:48 AM
It has been a year since I posed in this thread seeking advice, and thanks to everyone who replied.
In that time, the poor Grand Am has suffered some serious hail damage; about $2800 worth. That really sucks, especially on a car with so few miles in (previously) great shape.
I'm living in Saudi Arabia now, so the car just sits and is rarely driven. When I was home over Christmas break (I'm a teacher), I took the car in to get inspected. They mentioned that the BRAKE PADS WERE ON BACKWARDS?!?!?!?!?!?!?!?!?!?!? You can imagine how embarrassed I was, after all the headache this car has caused. I was flustered and told the guy how certain I was I got them on the exact same way they came off. Mind you, the pads coming off are the factory pads......
He said "oh yeah......a bunch of these cars came from the factory with backwards pads".
Is that true or was he just trying to make me feel better about myself?
Pads were switch, brake pedal feel immediately improved.
Sorry for the very late update.
No on to that pesky LIM leak.....
05-27-2013, 10:58 PM
i am told that when decompressing the piston not only remove the cap on the mc but, there is a valve thing by the caliper to release or take off to keep from any crud going back into the lines. i will be doing my brakes soon. can someone link to me anything i might wanna read over.
05-28-2013, 06:57 PM
Curt, I have never opened up the bleeder valve to compress the piston back in. I open the cap and slowly, evenly push the piston back in. I have no clue how many times I've changed brakes on dozens of cars, to guess low, and never had a problem doing it that way.
That bleeder is for bleeding air out of the lines, not for keeping "crud" out, the system is sealed up, as long as the lines aren't deteriorating, pushing fluid backwards wouldn't push anything into the fluid upstream.
vBulletin® v3.7.2, Copyright ©2000-2018, Jelsoft Enterprises Ltd.