Weird brake problem..

[roblun]

2006 Pontiac G6 Sedan, 54k miles, 4 wheel disc brakes, no ABS, brake light on dash not illuminating


I bought the car a little over a month ago. 2 weeks later the front brakes started dragging on my way to work( a 5 mile drive) and by the time i pulled into my parking spot the front brakes had locked up and the car couldn't drive without getting the rpms around 5500. just to go 5mph.
I let the car sit until the end of the day, at the end of the day the brakes released and i drove the car home, and at the end of the drive the brakes started dragging really bad again, not as bad as at work though. Well I decided to take the car to the dealer, (15 mile drive) and the brakes never got as bad as they did the first day. the suggested replacing the front left caliper, because it was hotter, made since to me so i did the job at home for a quarter of the price.
I took the car for a test drive ( 5 mile) and the brakes started dragging again, never as bad as the first day just enough to hurt my gas mileage and me to know and feel the dragging. So I decided to bleed the whole system. RR, RL, FR, FL, well the RR and FL had excellent brake fluid pressure, but the RL and FR only trickled out and had no brake fluid pressure. after all that was said and done the brake pedal wouldn't build pressure any more. and now the brake pedal goes nearly to the floor, then begins to stop the car. which is dangerous, and if you lock the brakes up only the FL brakes skids.
I took the car to a MIDAS and a Pep Boys, and they said the coulnd't find anything wrong with the car...
Well I drove the car from Chicago, IL to Virginia Beach, VA.
and the brakes didnt build pressure. Now, the FL and RR rims are covered in brake dust and the other 2 are spotless.

Obviously, no visible leaks, and im not losing any brake fluid, and the brake fluid is dirty, even after bleeding and replacing the brake fluid, its dirty again...

I don't know where to go from here...

[roblun]

Here's another piece to the puzzle. You know how your rotors get little rust spots on them after not driving the car for the weekend? Then after you driev the car they go away? Well my FR and RL rotors are covered in rust spots so they are obviously not being used? This makes me think the problem is in my brake fluid regulator, but i cant find the part on any auto parts site.

[grfnkl]

Have you checked your brake lines since you changed the fluid? Maybe one of the lines got kinked. I'm also thinking your master cylinder is causing the problem. You won't get a "brake" warning light unless you are low on fluid normally. good luck with the repairs.

[roblun]

Hey,
Thanks for your reply... Most of the lines are metal, but I will double check the rubber lines. I'm starting to think it's the master cylinder too.

[Firehawk7]

Originally Posted by roblun

Hey,
Thanks for your reply... Most of the lines are metal, but I will double check the rubber lines. I'm starting to think it's the master cylinder too.

Sounds like you might have gotten air into those calipers that are not working since the details changed after you bled them.

Not saying there isnt a problem but it did not stay consistant after you worked on it.

[roblun]

Now every time i bleed the brakes, no fluid is coming out of the FR and RL, it's been like this for a long time.
Is this my master cylinder?

[roblun]

Okay, I just tried bleeding at the master cylinder and the forward brake line, bled out like normal( a normal amount of fluid at a decent pressure). When i bled the back line(closest to firewall) it barely trickled out. So this means I need to replace or rebuild my master cylinder correct?

[XGamesJ6]

I would say so, most master cylinders have to pistons inside, and its a split system, in the event one line bursts, you have another one to protect you...and many cases its a diagonal split system, which sounds like what you have....one front and the opposite rear will work, while the others dont...it definetly sounds like a bad master cylinder.

Dont forget to bench bleed it before you put it in the car...just an fyi. although you probably already knew.

also if the car has ABS...try not to let the ABS module completely bleed out...from what i understand, those aren't too easy to get all the air out...but i could be wrong with the module in the g6. not to sure

[roblun]

Hey, thanks for your help, I forgot about this thread until XGamesJ6 responded and i got an email. I just wanted to say that it was the master cylinder that was bad. I thought it was so weird for a 2006 to have a bad master cylinder.... but that's what it was. Anycase anyone else has this problem, they can see what worked for me.