Help with expansion tank

[SilverGT3RS]

I’ve installed a coolant overflow/expansion tank supposedly made for LS1 engine swaps. I’m a bit confused on the radiator caps and actual hose routing. I’ve followed the attached diagram below, along with another diagram showing how I routed my hoses based on the expansion tank barbs, aftermarket radiator barbs and Vintage Air system I installed. I idled the engine as a quick test with the caps off for now, and idling it’s sitting around 185 degrees with the fan popping on low speed around 190 degrees . I’m not sure if I need pressurized cap on both tanks or just 1. Are there any issues with the way the hoses are run?

[LS short box]

On my LS swaps I just run a basic over flow tank from Speedway. It's not pressurized. I run a 15 lb radiator cap.

[kglowacky]

I also just ran a plastic oem overfow tank from rad to tank with a rubber hose. No issues in Houston at all.

[Joyridin]

Count me in with the others. Just a basic overflow tank and an 18 lb. cap. I did have one of those small stainless versions and it was always either empty or overflowing. I put a normal size on and it works great.

[kglowacky]

looking at your hand drawn diagram. I don't know much about vintage air BUT you show a crossover pipe and a shut off valve that then results in the heater hose flowing thru your overflow tank. If you have it set up this way then i think you need a pressure tank. I think you can get rid of the tee and let it flow back into the engine. My set up doesn't have but a heater hose in and one out no shut off or tees. I think vintage air is doing this because they want the hot antifreeze not to run through the heater core while the ac is cooling. I am in the process of completing my ac system using original parts so I may end up doing what you did if the coolant is stopping me from getting cold a/c.

[6600DURAMAX]

Originally Posted by kglowacky

looking at your hand drawn diagram. I don't know much about vintage air BUT you show a crossover pipe and a shut off valve that then results in the heater hose flowing thru your overflow tank. If you have it set up this way then i think you need a pressure tank. I think you can get rid of the tee and let it flow back into the engine. My set up doesn't have but a heater hose in and one out no shut off or tees. I think vintage air is doing this because they want the hot antifreeze not to run through the heater core while the ac is cooling. I am in the process of completing my ac system using original parts so I may end up doing what you did if the coolant is stopping me from getting cold a/c.

Wow - this got me thinking about my setup as well....... I have complete Vintage Air setup that I just completed install on. I probably didn't pay attention close enough but I did not see or run a tee in the two heater hoses but now that you point it out I am assuming that is what the valve is for - to close the flow of hot water into the Vintage Air unit in the cab? What happens when that valve closes ?

[6600DURAMAX]

I just relooked at the install instructions and don't see anything in regards to the use of a TEE ....??

https://www.vintageair.com/instructions_pdf/751170.pdf

[Joyridin]

Originally Posted by 6600DURAMAX

I just relooked at the install instructions and don't see anything in regards to the use of a TEE ....??

https://www.vintageair.com/instructions_pdf/751170.pdf

Many people have literally plugged off the heater hose fitting on the water pump with no ill effects. I have one of those loop hoses, but I probably should have plugged them also as my car has no heater.

I did not put a tee in front of the VA shut off valve and mine works fine.

[87chevy.com]

Originally Posted by Joyridin

Many people have literally plugged off the heater hose fitting on the water pump with no ill effects. I have one of those loop hoses, but I probably should have plugged them also as my car has no heater.

I did not put a tee in front of the VA shut off valve and mine works fine.

the point of the cross over tube is so the return flow from water pump that would go to the heater, runs back to the thermostat side for proper thermostat operation. When you block off the heater circuit, it no longer gets the proper flow if any on the other side of the thermostat.

On my 5 series bmw LS1 swap, at a long stop light or going through a drive through, I could watch the aftermarket coolant temp gauge start to rise, when I turn on the heater (not even, it opens the water valve and lets coolant flow in the heater core. almost instantly, the coolant temp dropped. I could blip the throttle some and it would also cool it down... Since I havnt installed the cross over tube, I just leave 1 valve open so the flow is like factory.