Quote:
Originally Posted by TButtrick
I would think that if you don't have a recovery system, you will most likely always have air pockets. When your car cools, isn't it sucking air back into the system through the cap port? If that air pocket is under your temp sender, that could be the source of erratic readings. I bought a cheap catch can from Jegs, ran a tube from the top cap expansion tank port to the bottom of the can (behind the can in the pic) with the petcock open and a tube from the top of the can to outside. Never a problem.
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It's a problem of physics. If there were enough room above the high point for an expansion tank with enough capacity then you would only need the expansion tank. Apparently this wants to expand about a quart total and the Kirkham has only about that capacity above the radiator hose exit (I didn't measure it before I installed it). So when the system expands and pushes out more than the Kirkham capacity it pulls air back in to the tank and into the hose, so that when it starts to flow again I'm guessing air is then pushed back into the radiator.
If the Kirkham had enough capacity above the radiator outlet it wouldn't be a problem. Since the system needs more expansion the choice is to fill the Kirkham full (which gives it enough to keep the radiator exit above water), and allow the system to expand into an auxiliary tank. My assessment is the Kirkham is made to fit in the available space and couldn't be any taller without hitting the hood. So for this engine's heat characteristics, it's just not quite enough.
This could all be accomplished with the original in-line cap/tube and a catch can with enough capacity and patience to bleed all the air out (and a very steep hill to get the fill cap above the thermostat housing). Meanwhile the Kirkham is installed, and backing it out now is more work than worth. Besides, as pointed out elsewhere, it looks cool!
I just never would have though that the system would expand so much. A quart is a lot of expansion and this misunderstanding is what led to so much churn.
If I need the overflow tank after moving to higher pressure caps the trick will be to find a place to mount it. The inside is already pretty cluttered.
Thanks to all who helped! This shows the value of the forum.