94 940 turbo. The car blows coolant out the cap as if it were overheating, but only if I drive hard. I can drive around town for weeks at 55 or under and no loss of coolant, but if go on the highway and run 80 for 10 miles it will blow out of the cap. I have replaced the cap (3 times),thermostat(180f), the radiator(was plastic and leaked), put on a new tank so would have warning light, flushed the system with flush, replaced the switches for the fan including the temp sensor under the intake manifold. The temp gauge never gets above center and I have checked the block with an infrared temp sensor and it is in the 180f range. Looking at the various pipes etc with the infrared gauge it seems to be the hottest right under the overflow tank where the hose from the turbo and radiator connects. Does anyone know how the water is supposed to flow though the turbo? Anyone else had this problem or any suggestions?