It's all brake related stuff, this week.
With the engine running, the brake pedal does not return. It does return when the engine is off. I'm guessing vacuum.
Any ideas?

 

your vacuume booster is probally bad. my f-150 had this problem when i got it runing the pedal would go allway to the floor if the booster was hooked up while running. I got a new one for about $60 from the local auto pars store. Another thing to replace while you got it appart is the master cylinder because they are only $12 and is cheap insurance. Also what year, model,and drive truck do you have?

 

I'm driving a 77 3/4 ton
Thanks

 

My plow truck does the same thing,and i spray the linkage behind the power booster with some P.B.Blaster,and work the pedal back,and forth for a moment,and this usually does the trick.the truck sit's all summer,and get's crusty.Just a Idea

 

I have seen many of our trucks with a fabbed up return spring from a rear brake kit for drums. It pulls that pedal back nice!

 

Hey. Thanks! Another cool idea.