Usually, one or more of the following components fail when an engine runs hot. A. the pressure cap; B. the thermostat; C. the water pump; D. radiator flow restricted by dirty buildup. Most of the time it's just one of these items, but failure of one can cause one of the others to fail, i.e., the thermostat fails and can cause the engine to run hot breaking loose old sediment in the cooling system and clogging the radiator. Questions: 1. Did you flush the radiator or did you have a radiator shop do it? A radiator shop will do it with a cleaning solution, will do a good job, and will then do a flow and pressure check. 2. Is the engine really running hot, i.e., is the guage or indicator light showing an overheating situation? 3. If there is "excessive" pressure in the radiator, the pressure cap may be the culprit. 4. If it appears there is steam in the radiator it could be from combustion cylinder pressure being forced into the cooling system due to a leaky head gasket or a crack in the block or head. 5. Some cars have removable plugs in the cooling system near the top of the engine that allows you to "bleed" off the air trapped inside the system which is caused by the radiator being below the level of the engine and not allowing all the cooling passages to fill up with coolant when you fill the system. You may be getting a false indication that the system is full when, in fact, the system has a considerable amount of air left in it. If you allowed the system to get too low at some time and then added coolant, you probably didn't replace all the coolant that has evaporated over the time it took for the system to get too low. You may even have to add coolant at the bleed screw point as well after you've returned the pressure cap to the radiator, or if it is a full pressure system, returning the cap to the expansion tank. 6. one less likely item is a hose weakened by being "drawn closed" by a flow restriction is now continuing to collapse and slow or stop cooling system flow. Usually it's the bottom hose and it usually occurs when the engine is revving at highway speeds. This brings up another point; does the engine run hot only when driving down the road or at street/highway speeds? It may be a hose collapse problem. Really, these things I have mentioned here are items the radiator shop would check, and maybe he has a few things more he will check since he's familiar with coolings system problems that can occur to your particular car. One thing is for sure - you have to decide what the replacement cost would be for your car if the engine fails due to this overheating. If your car is worth keeping it's worth proper troubleshooting before the engine is ruined by this problem. If some of these things I have mentioned can be verified without putting further heat-related stress on your engine, then, by all means, do them. But, I would be hesitant to continue to troubleshoot the problem by continuing to run your engine "hot" in order to do it. If you can't cure the problem without punishing the engine with these extreme temperature cycles, I would rely on the radiator shop or your neighborhood garage to resolve the problem even if it involves a tow truck charge, if you feel the car is worth it.
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