Puke Tank and Radiator Caps

[renaissance man]

It's my understanding that you should only have one point of "pressure" in your cooling system? This being the radiator cap. The puke tank or "overflow" while it has a cap on it should have the bottom pressure seal removed.


1. True or False?

2. Is your pressure cap regulated at the radiator or the puke tank?

[Trans-Am Jim]

The puke tank should not be pressurized, and have a vent at the highest point.

Pressure is regulated at the expansion tank with cap. Cap has two-stage valving.

It works thusly:
when pressure in the expansion tank (in my case, could be a radiator) exceeds 18 lbs. (that's my cap's setting; others may differ) the cap opens and vents excess fluid into the puke tank. I have my puke tank overflow set up to dump on the headers, evaporating any fluid venting from the puke tank.

When the car starts cooling down after shut off, a vacuum is created, opening the secondary valve on my cap, allowing any fluid in the puke tank to be sucked back into the system. The puke tank allows this, because it is vented, not sealed.

[Jack21]

Ditto. Puke tank is for fluid overflow and is not pressurized. Got a plastic coolant overflow kit from local Trak/Pep Boys and a Stant 7 # cap. As engine gets hot, coolant flows out of the pressure cap on radiator into the overflow tank. As engine cools, vacuum is created, and coolant goes from tank, back into the radiator. Cooling system "breathes" and keeps air out of the cooling system.

[renaissance man]

Thanks guys,

That is exactly how I have it set up. Pressure only at the radiator. Just needed to verify.

Cheers,