Topic: Radiator Overflow

[Porter]

I've noticed some vehicles have radiators that don't have an overflow bottle for the coolant.  There is just a normal cap on the rad without a hose attached to it going to an overflow bottle.  A cap something like these... http://www.summitracing.com/parts/GRI-KM-60/.   I think what I'm asking is the difference between a coolant recovery systems and non coolant recovery system (if that makes sense).  Do the non-coolant recovery system lids expand and let the extra coolant just drip out?

[Anderson0741]

Dont think so, the whole thing works on pressure, when the coolant levels are low it is pulled from a reservoir like a straw sucks up water.  This is easily added, some people uses pop bottles like mine did.