Hello all,
I've been having some major turbo flutter issues lately. I want to do the vacuum leak test but the instructions I've seen are very vague (see below).

"We have found leaking vacuum tanks causing this dtc. When testing the vacuum tank, care must be used or the results may not be valid. The vacuum tank has an integral check valve not noted in SI. To check the Vacuum Tank operation, disconnect the hose that runs from the tank to the Bypass Valve Solenoid at the solenoid and apply vacuum to the tank. The tank should be able to maintain vacuum with no decay. Note: If you remove the vacuum hose from the intake manifold and plug it and the decay stops the check valve is leaking, if the decay continues the tank itself is leaking."

Ok, so how are you supposed to 'apply a vacuum' to the tank, and if something is wrong how do you fix it? Any help is appreciated. Thanks.

 

Or just let the car sit for an hour, and then attempt to disconnect the hose from the solenoid leading to the tank. If you heard the vacuum release, it is holding vacuum.

 

Do the tank bypass mod and be done with it.

 

I thought about that. Where can you buy that vacuum hose? I don't want to cut mine up. I tried going to oreileys this weekend and they didn't have any of that hose. And when I look online for vacuum hose all that comes up is for the brake line or something..grrrrrrrrr

 

Go to O'Reilly and ask them for about 2 feet of plain rubber hose. Don't remember the size. Might have to find the old thread or guage the existing.

I wanna say the interior diameter is half inch.

They should be able to cut the hose quickly. It's not a specific hose or anything. The have big rolls of it.

 

Any chance it's just a bad purge evap solenoid?

 

I had a bad purge valve and it never caused tons of flutter that I remember.

 

Also, which one of the parts on the intake mani is the purge evap? There's one on the left that has three lines coming out of it, and then there's one on the right that only has one line which is hard and appers to be going somewhere on the driver side of the car (right side). Which one is the purge evap, and what is the other one? Can both of these cause issues or is it just one or the other?

 

The boost selenoid with the 3 tubes is on the left and evap purge on the right.

 

Could the boost solenoid be the source of the issue? It seems like I hear it's the purge most of the time but I don't want to leave any stone unturned.

 

2 things worth checking. Make sure your lower MAP has good connections. I personally think properly crimped and solderless connections are the way to go (good enough for aviation and marine standards), but most people on here seem to want soldered connections.

The other is that you need to make sure your K&N intake tube, and MAF are not contacting the shield. This was causing problems for me until I cut the shield with some tin snips (and repainted the open area).

I wouldn't worry about bypassing the tank if you hear that it is holding vacuum after an hour of the car being off. I think the solenoid is open when off, IIRC, so you can pull the hose at a number of places to test the tank for vacuum. Like just pulling off the hose leading to the BPV. You should hear the BPV close.

 

Which hose is the one going to the vacuum tank?

 

Follow the line coming from underneath the intake manifold. There's a good picture on this forum somewhere, but I don't have time to search for it at the moment.

The tank is directly under the IM.

 

You can test the tank vac with a Mighty Vac hand pump. They're like $35 but you use it for other stuff.

 

On another note, I tried the vacuum tank delete last night and it didn't help. When I put the vacuum tank lines back to the way they were before, I'm afraid that I mixed the lines up and put the one that's supposed to go to the solenoid on the IM and vice versa. How can I know whether or not they're in the correct location?

 

https://www.cobaltss.net/forums/4357883-post57.html

 

Make sure your TMAP, that's the MAP on the cold pipe, is facing the right way, and bolted down and sealed properly. Nothing hitting it. Did you ever throw P0236? That would indicate something up with the TMAP. Either wiring, or sealing issues.

 

That's the diagram I used to help me do the bypass. What I'm saying is that after disconnecting the two lines shown connected to the tank, when I re-attached the other ends to the solenoid and the intake manifold, I wasn't sure which line went to the intake manifold and which line went to the solenoid and I'm wondering if I took the hose that was supposed to go to the solenoid and attached it to the intake manifold and vice versa. I'm wondering how I know which line is the correct one that goes to the IM and which one goes to the solenoid.

 

If you are talking about the two lines that come from the vacuum tank, does it even matter? Does the vacuum tank how a valve in it that only allows one direction of flow?

I feel like it wouldn't matter.

 

It does have a check valve in it, and the flutter this morning has been really bad, so I'm wondering......

 

Oh... Yeah, I don't think there's any easy way other than to trace it back to the tank... You may need to get under the car to do that.

Always mark the hoses, or only work on one at a time.

 

Yeah, I should have thought of that beforehand I really want to take it to a dealer this weekend to get the GMS1 wiring re-done, so I might ask them to check it for me.