vacuum lines connected to mufflers
Thread Starter
Pro
Joined: Apr 2006
Posts: 647
Likes: 22
From: Norwalk CT and Boynton Beach FL
vacuum lines connected to mufflers
I just purchased a 2009 Vert, automatic trans.
When I was putting the rear license plate on I noticed that the two vacuum hoses there are supposed to be connected to the mufflers were cut off and just hanging there --- and the cut lines were not pluggged up or capped off that I could see. I guess this was done so that the previous owner got a louder exhaust sound all the time. But doesn't the vacuum come from the intake manifold and wouldn't leaving these lines unconnected and unplugged cause engine running problems. Engine seems to run fine. I don't understand how this system works and I want to restore the muffler operation back to stock so the exhaust sound is quieter unless I'm pushing it. How does this system work and if the vacuum does come from the intake manifold why does it not seem to effect the running of the engine (unless the vacuum is plugged somewhere else ).
When I was putting the rear license plate on I noticed that the two vacuum hoses there are supposed to be connected to the mufflers were cut off and just hanging there --- and the cut lines were not pluggged up or capped off that I could see. I guess this was done so that the previous owner got a louder exhaust sound all the time. But doesn't the vacuum come from the intake manifold and wouldn't leaving these lines unconnected and unplugged cause engine running problems. Engine seems to run fine. I don't understand how this system works and I want to restore the muffler operation back to stock so the exhaust sound is quieter unless I'm pushing it. How does this system work and if the vacuum does come from the intake manifold why does it not seem to effect the running of the engine (unless the vacuum is plugged somewhere else ).
Racer
Joined: Jul 2011
Posts: 464
Likes: 17
From: San Jose CA
a few things I would start with.
- check if its an orig npp equipped car (options sticker in glove box must state npp)
- IF so check fuse (passenger floor), maybe its there, maybe not, maybe has ben replaced w a mild-to-wild setup,
- IF NOT there may be a npp-in-a-box setup somewhere in the trunk or underneath,
- just connect the vac lines (at least in a temp fashion) and see if the valves close after engine is started,
.
- check if its an orig npp equipped car (options sticker in glove box must state npp)
- IF so check fuse (passenger floor), maybe its there, maybe not, maybe has ben replaced w a mild-to-wild setup,
- IF NOT there may be a npp-in-a-box setup somewhere in the trunk or underneath,
- just connect the vac lines (at least in a temp fashion) and see if the valves close after engine is started,
.
Melting Slicks
Joined: Oct 2010
Posts: 2,220
Likes: 16
From: Sugarhill Ga
see if the mufflers have the valves to open the baffles. if they don't, you may have an aftermarket system. have someone start the engine while you press your finger up to the hoses, if they are connected, you should feel vacuum. the hoses are attached to the rear of the intake.
Thread Starter
Pro
Joined: Apr 2006
Posts: 647
Likes: 22
From: Norwalk CT and Boynton Beach FL
right side? Left side?
Do I have to remove the fuel rail covers to see/find the vacuum port?
Anybody have a picture so I know what to look for?
Are the mufflers the only things that run on vacuum on this car?
Thanks
Racer
Joined: Jul 2011
Posts: 464
Likes: 17
From: San Jose CA
if its NOT orig equipment it MAY be connected there or in front of manifold.
https://www.corvetteforum.com/forums...ll-on-1lt.html
Thread Starter
Pro
Joined: Apr 2006
Posts: 647
Likes: 22
From: Norwalk CT and Boynton Beach FL
It turns out I have a stock npp system. Today I just connected those cut and hanging vacuum lines to the mufflers and presto --- everything worked. What I don't understand is why the engine was running OK with those two vacuum lines hanging, unplugged and unconnected --- sucking in gobs of air into the intake manifold. Seems to me the computer should have been throwing codes left and right. I guess I really don't understand how this whole system works. But for sure, the car now runs quiet --- too quiet -- and I will need to do something about that.
Thanks for all your suggestions and analysis. If anybody can explain why the engine ran find even though those two vacuum lines were open and unconnected --- then please explain.
Thanks
Thanks for all your suggestions and analysis. If anybody can explain why the engine ran find even though those two vacuum lines were open and unconnected --- then please explain.
Thanks
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Joined: Mar 2005
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From: Austin Texas
It turns out I have a stock npp system. Today I just connected those cut and hanging vacuum lines to the mufflers and presto --- everything worked. What I don't understand is why the engine was running OK with those two vacuum lines hanging, unplugged and unconnected --- sucking in gobs of air into the intake manifold. Seems to me the computer should have been throwing codes left and right. I guess I really don't understand how this whole system works. But for sure, the car now runs quiet --- too quiet -- and I will need to do something about that.
Thanks for all your suggestions and analysis. If anybody can explain why the engine ran find even though those two vacuum lines were open and unconnected --- then please explain.
Thanks
Thanks for all your suggestions and analysis. If anybody can explain why the engine ran find even though those two vacuum lines were open and unconnected --- then please explain.
Thanks
Notice the size, length and diameter of the power brake vacuum line right beside the NPP tap. Huge hose for a short distance run. If that one was open you would notice the vacuum leak.