So having an issue with the brakes on the car. It seems as you drive the car, and use the brakes, they slowly keep clamping tighter and tighter, so like after the first 2-3 stops the brakes are almost engaged enough to stop the car on their own. When you pull the vacuum line from the booster, they go back to normal, plug it in and drive a couple stops and same deal. I'm guessing a booster or master cylinder, but any other ideas?

 

If they release when the booster vacuum is removed, the booster is the most likely suspect.

 

That's what I'm thinking, but confirmation is good.

 

sounds like the master cylinder pushrod is out of adjustment...

If you can hold the brake pedal down firmly WITHOUT it sinking,The master cylinder is good.
If you can feel the brake pedal get harder after turning the engine off, the brake booster is good.
If you can get 2-3 soft pumps out of the pedal AFTER the engine is turned off, your check valve is good.
Hope that helps.

 

Check the pedal for free play. If the freeplay is tight then adjust at the MC pushrod to give a bit more freeplay.

If pedal freeplay is zero or not enough then the piston in the MC sometimes cannot move all the way back in the cylinder when the pedal is released (possibly related to normal booster function, not sure), so that the piston seal doesn't uncover the fluid port leading back to the reseviour. When this happens residual pressure in the cylinder doesn't escape through the fluid inlet / outlet port back into the reseviour. As the brakes heat up the trapped fluid expands, and the residual pressure in the hydraulic system increases and the brakes start to drag, generating more heat and then more expansion / pressure then more drag then more heat...

I had this problem on my CB7, and it caused the rear brakes to lock on, I've heard reports of a similar problem causing the front brakes to lock on. Increasing pedal free play slightly fixed it instantly. There is a specified pedal free play for a reason, even if it seems more than you'd think it ought to need to be.

 

TY for the help, I will try a few adjustments before I go buying parts.