Purplejchild

I know I'm scratching my head also. The dragging of brakes is what got this all started. There was 2 stuck front calipers that might have been the original problem, and after fixing that mybe the pushrod might have continued the problem. I don't know...

How could the length change and cause an issue?

I think I might have a breakthrough. I drove it today and it started to drag to the point it was almost locking up. I got out a d loosened the master cylinder from the hydro boost and that released the pressure, so I drove it home loose and put washers on and drove it the rest of the day and no dragging. So I hope this did the trick. Thanks for your advice and help...

When I replaced the old master cylinder the cap on it wasn't swelled or anything

I usually open the drivers front and when I do the pressure is relieved and the truck rolls foward a bit

One guy was telling me he thinks it might be the abs module. Since it not effecting the same wheel it bounces around one time it might be the back dragging and the next time it's the front. He recommends pulling all 3 abs fuses and driving around and slowly putting in each one back in till I can narrow it down to the right system. Any thoughts on this or do you think it's still in the master cylinder?

Let me ask you this. The hydro boost wasn't leaking when I replaced it. It was dry inside. The reason I replaced it was, after driving the truck about 15 miles and the brakes just start to drag the brake paddle would might a high pitch squeak then after I release the pressure in the brake line the squeak would go away but then redevelop when the brakes start to drag again. Now after replacing they just start to drag with no squeaking.

Is there anyway of flushing the system and flush the master cylinder I have now?

Someone mentioned that to me so I changed all flexible lines out. Nothing changed.

It's only locked up once and was the rear. Once I feel the brakes start dragging, I pull over and open the bleeder valve on the caliper and it's ready to go. As your going down the road you can feel the breaks start dragging.

I have a 2011 Chevrolet Silverado 2500hd 4x4. It has developed a dragging brake issue. I have changed all 4 calipers, brake pads,all brake hoses,master cylinder, and hydro boost, flushed with new fluid. It shows no check engine or Abs lights or codes. I can drive it between 10 to 20 miles and you can start to feel the brakes applying till it locks up. Then I get out and pop the brake line and relieve the pressure then we're fine for awhile till it starts all over again. I've taken a temperature gun to the calipers when its locking up and the front can be up to 180 degrees and the back up to 150 degrees, or it can be the back hotter then the front. I've taken it to a dealer and they have scanned it and with no codes they are saying it has to be a mechanical issue, but I have changed all the mechanicals except the hard brake lines. I am starting to think it's the Abs module or pump, but with no lights or codes I hate to put another 1000in this gamble. Any advice or help would be much appreciated. Thank you!