NPP vacuum issue need help!
Thread Starter
Melting Slicks
Joined: Nov 2011
Posts: 3,183
Likes: 265
From: Virginia
NPP vacuum issue need help!
I installed the NPP in a box kit on my base LS3 today and it works but the butterly valves don’t close all the way, you can barely tell a difference between on/off. The vacuum line is not pinched anywhere so I’m not sure what’s going on. If I push the actuator and manually close the valve while holding my finger over the vacuum port the valves stay about 90% closed when I release the actuator. So I’m not sure if I’m problem is not enough vacuum or if my actuators aren’t working exactly right. These mufflers came off a low mileage grand sport and it would be pretty odd if both were bad so I feel like it’s a vacuum problem, but why?? Any help would be appreciated.
Pro
Joined: Dec 2007
Posts: 595
Likes: 241
From: Maine
2022 C6 of the Year Finalist - Unmodified
Do they move freely by hand? If so my guess would be a vacuum leak. Check all your connections. Did you use the EZ Tap or the connection at the back of the intake manifold? Nevermind the last question, see someone asked it while I was replying.
Thread Starter
Melting Slicks
Joined: Nov 2011
Posts: 3,183
Likes: 265
From: Virginia
they do move freely they def aren’t stuck but it takes a good amount of force to close them… when I manually close the valve and put my finger over the vacuum port then release they don’t stay fully closed, only partially
Intermediate
Joined: Dec 2012
Posts: 32
Likes: 11
From: TX
I would get a vacuum hand pump and first check to see if you can connect it directly to both actuators and confirm you can close them with the hand pump. If I recall, mine both closed at around 10-12 inches. If that is working properly, you know the actuators are good. Next would be to connect the pump line to line coming from the NPPin a box and turn it on to see how much vacuum you get when enabled. You should see at least 10 -12 inches.
Thread Starter
Melting Slicks
Joined: Nov 2011
Posts: 3,183
Likes: 265
From: Virginia
I would get a vacuum hand pump and first check to see if you can connect it directly to both actuators and confirm you can close them with the hand pump. If I recall, mine both closed at around 10-12 inches. If that is working properly, you know the actuators are good. Next would be to connect the pump line to line coming from the NPPin a box and turn it on to see how much vacuum you get when enabled. You should see at least 10 -12 inches.
Thread Starter
Melting Slicks
Joined: Nov 2011
Posts: 3,183
Likes: 265
From: Virginia
Just to follow up on this for those in the same situation, I used a gauge and checked vacuum. I was good off the 3/8 line coming off the intake but had very little vacuum off the 9/32 lines that attach to the actuators. I used zip ties on all the connections of the 9/32 line and that fixed it, works perfect now!
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Thread Starter
Melting Slicks
Joined: Nov 2011
Posts: 3,183
Likes: 265
From: Virginia