timon,

Many times a radiator will get bugs, sand, dirt, misc crap stuck in the fins and this dramatically impacts the cooling efficiency of the radiator. You might use a garden hose and, with the engine off (obviously!) shoot some water through the radiator (directing the water jet from the engine compartment outward) I've used this technique many times to clear all the small bits of sand and gravel that our fine MA highway maintenance(?) puts on the highways in the winter here (October through May ;)

Hope that helps some,

TomD
'86 240
'93 240