[header] How to install a coolant flush kit [title] Check the engine to make sure it is no longer hot. [step] Loosen the radiator cap to release any pressure still left, and then re-tighten. [substeps] Many newer cars have the cap on the coolant reservoir instead of the radiator itself, but, on certain cars, there may be no radiator cap at all. 
In this case, emit the pressure by loosening the thermostat cap. [title] Place a pan or bucket under the radiator plug beneath the car to catch the old antifreeze.