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Capped vacuum line?

4K views 28 replies 5 participants last post by  kgschlosser 
#1 ·
I Replaced a busted intake hose/nipple today and found what looks like a missing vacumm line cap. Maybe I busted it off when I vacuumed out a mouse nest from under the engine cover.
Can someone tell me what this is and if I’m missing something?

Also with the silicone intake from DDM, the nipple is longer than the OE plastic one; Any solutions for reducing the length of the braided vent line or nipple?
 

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#3 ·
That my friend is not supposed to be capped. There is supposed to be a line that runs from where that cap was over to the front of the turbo. I would need a picture of the front of the turbo to be able to tell you what to do. IDK if you still have the factory turbo in your vehicle.

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If you look at the image above you can see a white circular thing on the upper left that is off white in color and has 3 bolts in it. There is a hose that is supposed to run from the nipple in the middle of that off white cover to where that cap was. You are also supposed to have another one of those black electrinic looking things attached to the front of the turbo
 
#4 ·
I can see the off whgite cap has a hose coming off of it in your second photo. IDK where that hose is connected. The vacuum lines are not connected properly in your vehicle I can tell you that much
 
#8 ·
Did you do this or was it like this when you bought it?? The reason I ask is the car must have a tune on it and the error code for the bypass valve must have been disabled because with the way the hoses are connected your check engine light should be on.

for some reason people did this kind of a change to the vacuum lines believing that in some way it made the engine create more HP. It does not do anything like that. The bypass valve is what takes the boost after the turbo and puts it into the intake before the turbo when you let off the accelerator. The turbo doesn't have brakes so it keep on building pressure when there is no longer a need for it. That pressure has to go somewhere. On older vehicles it would be blow off to atmosphere and it was a BOV (Blow Off Valve) that did that. On modern vehicles that use MAF (Mass Air Flow) sensors you can't take air that has been measured and just blow it off to atmosphere. So they came up with the BPV (ByPass Valve (aka recirculating valve)) to handle the excess pressure after the turbo. The BPV is a better system because the pressure doesn't just disappear like with the BOV so the turbo isn't starting off at 0 PSI if you decide to accelerate again. It is starting off where you were. This is a HUGE benefit if you vehicle is a manual transmission where you have to let off the accelerator when you shift the vehicle. The cars ECM controls how much to open that bypass valve and what has basically been done with that wye is the control by the ECM has been removed. This is not ideal as there are minor adjustments the ECM will be making to keep the pressure where it needs to be for how open the throttle plate is.
 
#9 ·
I bought it like this. Its a manual, aftermarket exhaust; I suspect with some kind of tune.. Out of the corner of my eye I swear that on occasion i see the check engine light flicker, like it is forced off.

Thank you. I appreciate your advice and will reconnect the vacuum lines. A Tube cutter should work to shorten the turbo intake nipple.

Was it also common for people to fill the rear end with epoxy or some other filler to stiffen it?
 
#12 ·
No there is no aftermarket BOV. and even if there was you would still have the hoses connected to the solenoid properly.

No reconnecting the lines will not effect the tune at all.

The trunk pan is made from fiber reinforces plastic so maybe that is what you are seeing? It's not metal. It should be blackish in color. I have not heard of doing anything with an epoxy in the trunk. It wouldn't do a whole hell of a lot unless it was 2" thick and it would probably end up cracking is it was actually secured to the frame rails properly. Heavy as well. Would have to see it to know what you are dealing with as far as that goes.

What does you boost gauge read when you have the accelerator pushed to the floor at 5000 to 6000 RPMs?? If there is no tune it will read 14-15 PSI at sea level and at high altitude 6000+ feet it will read closer to 18 PSI. If you have a tine those number will be 4 to 8 PSI higher depending on the tune. I do not believe you have the GMPP tune because your TMAP sensor in the pipe that connects to the throttle body has 2 bolts/screws holding it in. the upgraded ones that come with the GMPP tune has only one bolt. The GMPP tune was a tune that GM offered for the vehicle that would increase the HP to 290. It is an EPA and CARB compliant tune so if you live in California you would not have an issue passing emissions there with it.

The boost reading is an easy way to tell if a tune has been done.
 
#15 ·
No there is no aftermarket BOV. and even if there was you would still have the hoses connected to the solenoid
I beg to differ KG. This was actually a “thing” on the forum back in the day. Although i was mistaken as it was on the cold side charge pipe.
Not saying this is what the OP has, just that the odd hose routing warrants at least a check before dismissing.

 
#20 ·
KG, The metal tube is glued into the red intake hose so it seems that connection is good. Can add a clamp for good measure though. The metal tube as received has no ridge like the OE hose for the black plastic end of the vent hose to bite over/onto.
Have not checked boost lately, the first few days I was running around i know I saw boost up to 18 psi on the dash display; not sure at what rpm.
 
#21 ·
it's probably not "glued" in. The coupling is made from silicone so it is more then likely a very tight fit getting it in there. If you want to shorten up that metal tube take some tooth picks and slide them down between the coupling and the metal tube and then shoot some Windex there. wait a couple of minutes and you should be able to turn it and pull it out.

what is the elevation where you drive the car?
 
#25 ·
OK you have a tune then. I don't think it is the GMPP tune as that would require different MAP and TMAP sensors. It is more then likely a Trifecta tune. If you e-mail them your VIN number they might be able to look it up to see if they are the ones that tuned it.
 
#28 ·
Y

Found some time in the garage today and got the intake And vacuum lines corrected. Took it for a ride and all is well. I was mistaken about the max boost; I am seeing it peak at 14, then steady at 13 and then dropping to 0. Thank you again for your help.
 
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