c3 78 vette L350.

I thought I'd post this good news story to helper others.

So after reading thread after thread and all the videos out there, i found a link to a page where they walk you thru testing vacuum. after buying a vacuum tester at harbor freight for 44 bucks, i found a few T's that were old and worn. I bought a set of them on amazon for a few bucks and replaced the 2 i needed. the hoses seemed fine. Now on to the fun part. I tested the actuators and they weren't holding vacuum. As a matter of fact it was pretty bad. I bought a vacuum pump attached it and they came up great. when I reverse it they came down just as well. vacuum test kept showing bad though with the handheld pump with the gauge. Then on to the relays and the same thing. I thought oh well i'll buy both relays and actuators and swap them out. Once I got them I started with the relays since they seemed the simplest of the two. Once I did that I decided to test it. vacuum was PERFECT. UP and down no problem. So the vacuum test on the actuators was garbage. Thank goodness I tested after relay install. I sent back the actuators and saved 150.00 bucks. While I was at it I also changed the Vacuum Hose Check Valve & Filter since I was in there and it was cheap and easy to do.

Moral of the story, buy a vacuum pump, put it inside the car with window up so you can hear, plug it into where the vaccum check valve is, and listen for leaks. you'll hear them trust me. testing with the handheld vacuum pump and watching the gauge fall is what confused me. replace the relays before spending money and time on the actuators.
Good luck all

 

I'm confused as to how you're checking compression on a vacuum system.

 

http://www.corvette-101.com/vacuum.htm#relay

Hand Held Vacuum Pump: Used to verify the hoses and vacuum components will hold a vacuum.

maybe i used the wrong jargon. thanks for the correction.

 

I tried 2 different new check valves, they were both bad. I could blow air both directions through it. You have to plug one of the 3 holes to check it. I'm not sure they are making the new ones correctly.

 

actually the one I had would hold vacuum against my finger and the hoses just not the actuators which leads me to believe they are probably in the process of failing. What should have tipped me off was the fact that the vacuum pump opened and closed them no issues. Eventually I’m sure they have to go