My car holds good vacuum, about 17 to 18 inches on a brand new motor. However I was just going through the lines to double check that I had no leaks. It turns out that I have a couple issues.

Should all lines involved hold perfect vacuum? I only ask because I know there are check valves here and there, and I don't want to waste time if the line isn't actually supposed to hold vacuum.

For example, the HVAC line that comes from the wiring harness and tees into the passenger side of the plenum won't hold any vacuum.

Also, the line that heads down to the reservoir ball holds no vacuum either. I'm pretty sure that isn't supposed to be happening. Could this be a possible reason my cruise control fails to work? It's on the same line.

What kind of problems can these leaks cause? Is it difficult to service the vacuum ball?

Thanks!

 

Only lines behind a check valve such as the one that goes to the brake booster will hold a vacuum.

All the other lines getting a vacuum source from the engine won't hold a vacuum when the engine is off however they also shouldn't be leaking anywhere while the engine is running. None of those lines should require a vacuum signal when the engine is off.

The brake booster however does. It's to provide a couple of power assisted brake pumps to get you stopped if the engine dies. Once the vacuum reserve is gone, there's no power assist.