Not sure if overflow tank is the right term, but I mean the plastic bottle on MB cars that you fill with coolant and it has the radiator cap. Does anybody know what the pressure rating is on one of these? I assume at least the value of the pressure cap, I am wondering what max pressure it can hold.

thanks
Fred Emmerich

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MB-less

The proper term is coolant expansion tank. As you mention the maximum pressure rating is greater than that of the cap. Not sure of the specific value.

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Fred Hoelzle

It all depends on the vehicle the cap is installed on. Mark

That should be designed to hold the same amount of pressure as a radiator if it is the type with a radiator cap on it.

And with that said, they make radiator pressure testing tools which have a pressure range of up to 30 psi.

Other than that, with things which hold pressure, there is...

-The pressure they typically work at.
-The "rated maximum pressure" (higher).
-And then the pressure they will burst at during testing (even higher).