Rather than adding this on to the thread of the brakes not working, I thought it should be a new thread. To recap, we are working on a 1970 Road Runner that was last driven at the Mopar Nationals in 1999 and trailered home and hasn't been started since. We got the motor running and then fixed the brakes with help from FBBO on another thread. But the power brake booster was not working. So I contacted Harmon's and got a quote on rebuilding the booster. He said it would take 3 weeks, and that's fine, but the owner wants to take it home next week so he will have to do it at home. The owner called me last night and said that there is a check valve in the power brake system. I told him I would check it out. The power brake hose goes from the intake manifold to the check valve and the check valve pushes into the booster. So this should be easy enough. I pulled the check valve out of the booster. So if you start the engine now it should almost not run because of the massive vacuum leak. I started the car and it ran perfect. So the booster wasn't getting any vacuum, that's why it's not working. So that means there is a 100% chance the check valve is stuck. So I removed the check valve and shook it (like a PCV) but it didn't rattle (like a stuck PCV). So I removed the check valve and sucked and blew on it and it appeared to work properly. So I put it back together and started the motor again. The power brakes still didn't work. I don't know what's going on but the check valve can't be working. So I removed the check valve and used a fitting to plug the hose straight into the booster. The power brakes didn't work. So I removed the hose and blew through it. The hose is not stopped up. So I started the car without the hose even on it. It ran perfect. Now I'm looking straight at the big vacuum fitting screwed into the intake manifold knowing it's hard for that to malfunction. But the car is running perfect. It's nearly impossible for a fitting that large to "crust over" completely. (Don't get me wrong, where I live mud daubers can fill any hole, and very quickly, but there was no signs of mud daubers on this car.) So I got a straight punch and stuck it down into the fitting. It stopped about 1-1/2" down. So I lightly tapped and it broke through. I put everything back together and now the power brakes work. So the moral of the story is before you send your brake booster out for rebuild, check your vacuum. Strange things can happen.
