2007 Silverado Classic Brake issues…PLEASE HELP!!

[CCMC]

I’m having a brake issue with a 2007 1500 Silverado classic. I’ll give a little history of the problem..it began with a bad booster, could hear it blowing air while pumping the brakes, oil in the booster and the brakes not acting quite right. So the process began, I figured since I was replacing the booster, I’d replace the master cylinder, fluid was nasty and figured I kill two birds with one stone. I replaced master cylinder and booster, bled the brake system, test drove it and brakes worked as they should!! Thought I was done…not hardly!! My son drives it for a day or so and advises me that the brakes had locked up and needed help. Once the brakes cooled, I was able to drive it to the mechanic shop, I did this because I had no idea why and had no time to troubleshoot it at this point. So fast forward 3 weeks…and multiple problems caused by contaminated brake fluid…new calipers, new ABS module, tried 4 different aftermarket master cylinders, multiple bleed cycles, GM saying to use aftermarket because the one we need is discontinued (which we’ve used 4 different ones). After all of this, the shop says, front brakes are still dragging…shop said if they break the line at the master cylinder the brakes release…so I mentioned, “I still have my old master cylinder (confirmed leaking) wanna try that to see if it makes a difference? Low and behold, old master cylinder works no dragging, and the brakes operate like they should. So bingo found the problem, I’ll just order a new GM master cylinder and go on down the road… not so fast…after multiple superseded gm part numbers still can’t get the correct master cylinder to fix my sons truck!!

 

Sorry for being so long winded…I can fix pretty much anything, there are two things I haven’t been able to fix, is a karaoke microphone for my daughter and this truck! 

 

I’m hoping someone out there has had the same issue or am I missing something really simple…any help will be greatly appreciated!!

[CamGTP]

Can you take apart the master cylinders you have and just swap seals to make the OEM stop leaking?

[CCMC]

CamGTP…A rebuild kit did cross my mind, but not swapping o-rings etc from a aftermarket…if I remember correctly, there is a snap ring holding the plunger assembly…might be an option!! 

[txab]

Have you got the brake booster travel length adjusted properly? iirc, that comes into play when replacing. Been too long since I had to replace a booster

[CCMC]

I’m not sure if the rod is adjustable, at this point anything is possible!! I’m wondering if it’s a reman tolerance issue.
 

If that is it, would you be able to relieve the pressure at the master cylinder and release the front brakes?

[txab]

Maybe some else will chime in. As I said been quite a while since I did one but do remember adjusting the rod on that one.

 

Also I would think your mechanic would have taken care of it if it was an issue

Edited February 20, 2022 by txab

[CCMC]

Ok I have an update…tried the original master cylinder and it worked….for about a week and now I front brakes dragging again…. I’ve got some front brake lines ordered but I’m thinking this could be a booster issue now. I did check the original booster and there is no adjustment visible. Any one have any other ideas?

[txab]

Here's what I was talking about possibly adjusting. whether it could be causing your issue, not sure. I know it affect your brake pedal

 

 

Edited March 3, 2022 by txab

[CCMC]

Awesome!!! Thank you!!! I’m gonna try and mess with it this weekend!! I’ll let you know what happens.

[txab]

I'm surprised you haven't had many others to chime with their experiences. Did you ever persue a rebuild kit, if they make one anymore, for your original MC?

[CCMC]

That will be the next thing!! I did look at the factory booster today and I don’t think it’s adjustable…maybe the after market boosters are adjustable. 

[Sbrowder]

Did you ever figure out what was going on and how to fix it?  Same issue with my kids classic.  We have changed out so many parts and nothing seems to be fixing the dragging and locking up.

[PunchT37]

On 3/2/2022 at 8:08 PM, CCMC said:

Ok I have an update…tried the original master cylinder and it worked….for about a week and now I front brakes dragging again…. I’ve got some front brake lines ordered but I’m thinking this could be a booster issue now. I did check the original booster and there is no adjustment visible. Any one have any other ideas?

Brake lines. Meaning brake hoses?

[asilverblazer]

On 9/15/2024 at 1:13 AM, Sbrowder said:

Did you ever figure out what was going on and how to fix it?  Same issue with my kids classic.  We have changed out so many parts and nothing seems to be fixing the dragging and locking up.

Really old thread, but the idea is that there might be a tolerance issue with the master cylinder, brake booster rod. The rod length might be keeping the brake booster slightly 'open' applying the brakes.

 

A couple things to check, unhook the vacuum line from the booster and plug it so the engine doesn't have a massive vacuum leak and carefully test drive. You won't have power brakes so it will be difficult to stop. If the problem doesn't present itself then proceed with brake booster master cylinder diagnosis.