do i need a cooling system resovior ?

YY1 said
As long as the overflow tube is below the water level and the cap is correct for a return system, yes.

Those "engineered" bottles that have the hose connection plumbed to the bottom of the container guarantee the hose is always at the lowest level.

I have mine cut so that it is about 3/4 of an inch from the bottom of the bottle.

Works very well.

I try to keep the bottle 1/2 full so that it will hold overflow and also have coolant to suck back in.

Does anyone know if the cap that came with the Champion radiator would work for coolant recovery? If not, what cap should be used? I remember the "old days" when the coolant recovery kit came with a cap that said coolant recovery.