upper radiator colaping

[senatorrick]

I have a 07 Duramax 130k when its cold upper hose go almost flat. after warming up hose is normal. I have replaced cap on tank why would this keep doing. also replaced water pump 10k ago. ANY SUGGESTIONS

[rapidoxidationman]

Are you sure there's not excessive air trapped in the system? Air contracts and expands a lot more than fluid does with temperature changes.

[More Power]

The vents in these surge tank caps should vent negative pressure, which would prevent hose collapse. I don't know of an easy way for a typical truck owner to test these caps, but I'd bet the problem is the vent in your truck's surge tank cap.

[V65_MAGNA]

I have 3 of these trucks and they all do it. perfectly fine just shows there are no air leaks therefore no lose of fluid and that it is indeed sucking the fluid back into the system from the overflow tank.