2006 Chevy Malibu Brake Issues
 

Ok, so we've been having an ongoing issue with my mom's brakes and I figured I would post on here to see if any of you car gurus have had any similar issues or ideas for us. Here's whats been going on:

The car was bought in 2006 and had no real problems until this past fall. The brakes would basically lock up and the car couldn't be driven anywhere. We took it in to the dealership to see if anything was still under warranty. The ABS unit was so they replaced that this past fall along with the rear brake pads. They mentioned that they had trouble closing the calipers but it was stopping fine so we thought it was fixed. Then towards the end of April the brakes started locking up again. My mom said it felt like the emergency brake was on but it wasn't. She would let the car cool off for 20-30 mins and then it would be fine for a little while (meaning hours, days or even a couple weeks). It happened a few more times and she finally took it in. They said checked it out and couldn't see any visible problems but that it could be either the master cylinder or the brake boosters. They decided to change the brake boosters. We got the car back and it was running fine. We even drove it down to Lexington and back this weekend with no issues at all, until last night when it happened again.

Now, I'm starting to get skeptical about this dealership but they have seemed to be pretty straight forward with us and gave my mom a rental car to use at no cost to her this past fall. We've even called around to other mechanics and checked with our normal mechanic and he's as stumped as the dealership.

So, has anyone dealt with this kind of problem before? Any solutions or ideas?

I'm ASE cert in brakes so I'm not talking out my ass here.....

Sounds like its ABS related. Could be off on this, but I'd start looking at that. Just skimming through the diagnostics on it there is a release valve that operates during intialization on startup. If that fails to fully open again then you'll have slow or no release.

What did the dealership replace in the ABS that was under warranty? How many miles are on the car? Any accidents or repairs prior to the problem?

Dealership can only fix the problem if they experience it or have a code to go on. THey sound like they are trying to make sure you are taken care of. Sucks to have an on going issue that is plaguing you but thats the way it works sometimes. I've been chasing a gremlin in my PT for a year now. Finally figured it out 100% the other day, but have thought it was everything from a bad sunroof motor to the cigarette lighter shorting out. Can't troubleshoot something that isn't broken.

I believe it has right around 50k miles. They replaced the entire ABS unit. It was in a minor front end accident a couple years ago but everything was fixed and checked out. She took it back in today and they said they were going to replace the ABS unit again.... Luckily that's still under warranty so it won't cost us anything but hopefully it actually works this time.

Most likely what they are replacing is the ABS computer (EBCM in this case) and not the valve pack (BPMV.... yeah... another acronym). Looking at the schematic there's hardly any way that a short or open could cause the problem unless it was internal inside the EBCM. This is of course assuming its ABS related. An easy check to see if it is.... Wait until the car does it again. STop the car, unplug the ABS, start the car again and you'll have an ABS light. If the problem instantly goes away, its ABS electronics related. If not, it could still be the BPMV sticking from the previous initialization along with the rest of the untested components in the system.

Just found that there is a test to command each of the solenoids on and off to isolate problems and to bleed the system. THe stealership should have that scan tool to do that though. Would think they'd have thought of this already too.
Before you unplug the ABS .... make sure you can clear the ABS codes after.

This car seems too new to be this but FWIW I've had the flex line swell up on a car one time and I didn't have any problems stopping but it did cause the brakes to release slowly and make them drag, like a check valve. Wonder if it could be this since over time it goes away.

BTW mostly driving on the Hwy you would not notice it as much since you don't use your brakes as often as city driving. When I first noticed the problem it was stop and go driving.

Assuming the op has been taking it to a gm dealership, they should have a tech2 scan tool. Id take it to a different dealer and pay for an hour of diagnostic time and see what they say. Give them your reciepts of what the other dealer did and any other related work that was done.

Do all the brakes lock up? Or is it just one wheel causing the problem? A pinched brake line can cause this same problem.