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I'm suspecting the hvac line in my 99 is disconnected behind the manifold, when I have the air on feet only it blows to defrost and feet and I'm getting a sort of vacuum sound when going 1500-2400 rpms before its drowned out by exhaust, do I have to take the manifold off to adjust the line and what position behind the manifold is it generally? To the drivers side/passenger side or in the center behind it?
Can only hear the noise under load, not throwing any codes. I'm pretty certain this isn't the line but I just want to make sure, this picture is on the driver side
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Last edited by 5thgenvette; Apr 6, 2016 at 11:46 PM.
Not sure what line you are talking about in the picture. The vacuum comes off the very back of the intake and goes to the tank below the battery. It then feeds thru the firewall to the HVAC unit.
I have good pictures at home if no one else beats me to it. Battery acid can destroy the tiny black plastic line in that area.
I was talking about the little black elbow in the pic, do I have to take off the manifold to get to it or would it be possible to check if it's connected just by feel of hand?
Is the small line with the plastic elbow tip on the end the line that should connect to the back of the manifold?
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Yes, that is the line. It also runs under the battery and back into the firewall. I had a similar issue and replaced the whole line back up into the firewall. I don't have good pictures, but maybe these can help you?
That little rubber 90 fitting and the NYLON line goes into the MAIN HARNESS on the back of the engine on the passengers side. It like THIS where it enters the harness:
The hard line from the rubber 90º elbow should run down to the area shown in ehillard0's photo and connect to a manifold. You'll want to take the RF fender off.
See pic, bottom hose should be coming from your intake.
Check the HVAC hose and see if it "holds" vacc.
ETA: also, you may be able to check the vacc "source" hose and see if you have a leak somewhere other than at the intake manifold elbow. I was able to discover a broken hose from the AIR pump just by blowing into it and hearing a whistle somewhere between the AIR pump and the fender, somewhere inside the harness bundle the hose was routed through. Since I wasn't about to open up the harness bundle, I just ran a new rubber hose along it.
Last edited by huesmann; Apr 11, 2016 at 09:54 AM.
Reason: added info
I just went ahead and took my whole manifold off the clean everything up nice, the problem was just that the little line wasn't in fully. Once again, thank you CorvetteForum members
1999 hvac line
