Lower radiator hose spring

[Steve Wood]

Okay, we all know that springs are put into some lower radiator hoses and the reason is supposed to be prevention of hose collapse when the water pump sucks hard.  I have seen the lower hose collapse on engines on the dyno so it can happen.

Yet, new hoses no longer seem to come with springs.  Now, I am trying to figure out how a hose can collapse on a modern cooling system that has no air in it.  Liquids are not compressible.  If there is no air to begin with, and the system is filled to the brim with coolant (burped thru the reservoir), then how can a hose collapse in a closed loop system such as they are?

None of the engine dynos I have seen have gone to the trouble of being air free in the coolant system

[earlbrown]

The high pressure side of the pump causes the upper hose to swell a little,  then displaces some coolant past the radiator cap.  With the lower volume of coolant occupying the same space atmospheric pressure can collapse the lower hose.


Or it's gremlins.

[Steve Wood]

strange that many new cars don't seem to have them....but, then, they don't have high volume pumps either

[earlbrown]

I've never performed a precision squish test with a newer car's hose that's purpose built without a spring.  I think they run higher pressures along with temps too.