slipslapjack

2006 Cobalt ss/sc
I just completed my option B reservoir hose install (with dual pass) and basically tested it out to my satisfaction. Despite reading all the forum comments, it was not clear to me how the system really works with respect to bleeding air and whether the hose from the option B tank had to gravity feed the dual pass plumbing.

What I discovered was that with the pump running, the output from the heat exchanger bleeder valve is a fair amount of moisture and air bubbles. This causes sufficient pressure increase within the option B tank to push fluid over any additional elevation the return hose may have as it makes its way to the dual-pass plumbing tee. This was important to me as I put my option b return hose through the cavity in the engine bay wiring tie-rail (see photo - which has the supercharger removed). To go thru the cavity, the hose has to climb in elevation and effectively forms a crown or high spot in the intercooler fluid circuit. I wondered how this was going to work - if at all. But - I wanted this path because of the minimal clearance experienced (too tight for my comfort) if trying to go direct and close by the supercharger pulley/belt. Plus - I noticed on another forum post that John Powell (Powell racing) said he used a smaller dimension fuel injector hose to go thru the same cavity for his option B install - and used a chisel to create a larger opening. Since I used the 3/4" hose, I did enlarge the one opening using a dremel tool - filed it smooth and then spray primed and painted the opening to minimize any future rust issues.

I also placed an in-line adapter/connection at point "A" on the photo. I used this spot to open up the plumbing and poured coolant down it - to do an initial "priming" of the closed system (not sure if that was absolutely necessary or not). I used this spot because when I initially tried to place fluid in the option B tank - it just sat there - and would not gravity feed all the way to the dual bypass tee and effectively to the pump. Eventually, I did an experiment with the plumbing opened up at "A" - and I turned on the intercooler pump. To my surprise coolant started pouring out on the ground from the open pipe leading back to the option B tank. Obviously, enough air pressure from the bleeder valve was pressurizing the option B tank - and pushing coolant thru the hose and over the rise where I had placed the hose in the wiring tie rail cavity. This convinced me that the fluid from the option B tank does not have to gravity feed all the way to the dual pass tee (this is contrary to a currently posted youtube video making the opposite claim).

With all that info, I did a final prime of the system, added some more fluid to the option B tank, and closed up the plumbing. Later, when I ran the intercooler pump for a couple minutes, the coolant level in the option B tank started to go down - and a layer of bubbles was forming in the option B tank. Basically the intercooler fluid circuit was working with the hose path I elected to use.

SSJ