I read somewhere it was developed for road racing. It stores vacuum to help operate the waste gate. Doesn't seem to do anything for daily driving.

 

GM or some other company must have replacement tanks, I have read on the Cobalt site this is required for daily driving

 

Vacuum reservoirs allow operation of the power brakes and other vacuum operated accessories when sufficient engine vacuum isn't present (I.e when boosting or you're on the throttle at all). You'll probably want to reattach that.

 

This tank is not part of or tied into the brake vacuum booster.

 

Nope, its tied into the pcv system which is where the brake booster draws from. Turbo cars can't have the brake booster tapped into the manifold like na cars.

 

Really ? This big single hose goes straight from the intake manifold to the brake booster on my SS.
It doesn't branch off or tie into anything else.
You may want to change your post above.

 

Well, I'll revise my statement, but only in terms of the pcv bit which was my bad for looking at a photo and not opening the hood on my car. The brake booster and both vacuum reservoir lines all appear to be plumbed into the intake with what looks like a valve in line on the left most vacuum reservoir connection. I would still think that the function of the reservoir is to provide enough of a drop in manifold pressure so that the vacuum brakes booster can work correctly (i.e. faster than manifold pressure drops by itself when you let off the throttle). Should be simple enough for the OP to test. Drive under boost then quickly hit the brakes and see if they feel boosted or not.

 

The brake booster is a reservoir. It can store vacuum because it has a check valve at the booster end of the hose.
Maybe in the old rod days of high lift,long duration cams you would need a storage reservoir because of no vacuum at low rpms. I don't think that's the case with the LNF engines.

 

OK. Got curious and decided to look into what this vacuum canister is for. It is just for the bypass valve system on the turbo.
It is NOT part of the PCV or the brake booster vacuum.

The picture below shows the vacuum hose routing and direction of vacuum pull.
Yellow: goes to and from the canister under the manifold.
Blue : is the hose to the lower charge pipe(nipple next to the lower Tmap sensor )
Red : is the hose to the bypass valve on the turbo

Now that valve that connects them together in the middle ? Not really sure how this works or functions.

 

Does anyone have the part number for the vacuum tank?