1993 Corsa 1.5TD GLS Manual Diesel My corsa once in a while overheats (boils over) for no apparent reason. I have changed the thermostat, pump, radiator and I have tested the cooling fan on the radiator, which kicks in at the right temperature. I noticed in the Haynes manual they mention there is an oil cooler and a oil cooler thermostat, can somebody explain please the theory of these items, and if they might be the cause of my problem? TIA Mark Scotford