Dragging Brakes

Hey all,

Reaching out to the community for some brake issue diagnostics help. I feel like I’ve watched 50 YouTube videos at this point and want to get some opinions before replacing stuff.

All four of my brakes are failing to release on my truck and the front brakes seem to drag more than the rear. I might be feeling the drag on the drive train on the rear wheels. They take some muscle to move but aren’t locked up like the fronts. After accelerating the truck to 55 or 60 mph the brakes will release and the truck will surge forward.

Here are the things I’ve checked so far:

1. Pulled the front calipers and manually pushed in the pistons to confirm they are not seized.I also confirmed the hubs spin freely with no brake pads in.
2. Cracked the bleeder valve on the calipers and the brakes free up (although they still drag some).
3. Cracked the flex hose fitting and the brakes freed up.
4. Cracked the line coming out of the master cylinder and the brakes freed up.
   
5. Unbolted the master cylinder from the brake booster and the brakes stayed locked up.

This would point to a faulty master cylinder correct? I’m reading conflicting information on if a master cylinder can cause an issue like this.

I don’t know if this is related or not but if I hit the brakes hard while the truck is running the brake pedal will slowly depress another centimeter or so.

 

Well if for some reason the port in which the fluid returns to the master cylinder reservoir is clogged or the return reservoir is full then theoretically yes. If cracking every valve and connection on the way back up to the master cylinder releases pressure from the lines and allows the brakes to release then that's all I can think of that would cause that issue. Does your brake pedal come all the way back to the normal height as it did before you started having this issue? Can you pull up any further on it?

 

I’ve only owned the truck a month or so not history. It’s had the brake issue the whole time. The brake appears to be in a normal position and cannot be pulled up any further.

 

From your testing it appears the master cylinder has failed .

The fluid is now behind the piston not allowing the brakes to release in a normal fashion.

Given enough time sitting the brakes might release then might not.

Be very careful many poor quality remanufactured parts around.

Good Luck!

 

Maybe check the pedal Freeplay adjuster under the dash? Possibly not releasing pedal pressure?

 

Updating my progress here.

so today I decided to change out my brake fluid just to see if that does anything before replacing my master cylinder.

I removed most of the fluid from my reservoir and filled it up with fresh fluid. I then hooked up my new Motive pressure bleeder and pressurized the system to 10 psi. After cracking the passenger rear bleeder I get a drops of fluid coming out. Moved to the front brakes to see if there is a difference. On this one I totally remove the bleeder valve and a tiny trickle comes out.

So I cannot move fluid from my reservoir into the system.

I’ll proceed with changing my master cylinder.

 

Just a thing to note- on the rear brakes, you need to bleed the proportioning valve as well. If you are having issues with getting fluid at the drums, you can try disconnecting the lever arm connected to the valve and raise it all the way to the bed and ziptie it. This should open the valve all the way and let full pressure through the lines. I realize this may not be your issue as you should see ample fluid movement at the front calipers regardless of the LSPV, but just throwing it out there for completeness' sake.

I believe I asked already, but do you have ABS?

 

Good to know thanks! I do not have ABS.

 

Not having ABS is going to help you, or at least eliminate the possibility of air being trapped inside the module. So be stoked on that.

Out of curiosity- What happens when you open a bleed valve and have someone step on the pedal? Does it move fluid?

 

I can get a little fluid out the first time I step on the brakes and crack the line.

after tightening the bleeder, pumping, and hold/crack again I get no fluid movement.

 

Alright replaced the master cylinder.

My brakes no longer lock up or drag. The problem appears to be solved.

Thanks all. That was a great learning experience.

 

Glad you got it straightened out!