Why is a car overheating even after changing the water pump and the radiator?

Always should replace thermostat at same time; if this was not done, do so. Rust and gunk in the cooling system from a corroded radiator will often jam and damage the thermostat. Conversley, sometimes a corrding thermostat sets of the entire process by both stricking and by sending hicks of rust to the other cooling system components (radiator and water pump). After engine idles for a while (but prior to overheating) gently squeeze the large hose attached to the top of the radiator. Is it getting warm? If not, the thermostat is likely not working. The thermostat should click and open the route for the top radiator hose, when the temp gauge is no farther toward "H" than at or just below the halfway mark, or just above, on most vehicles. Once the thermostat opens up the route for the upper radiator hose, the temp gauge should fall quickly. If the thermostat wasn't replaced, appears to not be functioning, and is easily accessible and visible, tap it with a hammer (not hard enough to damage it)and see if it becomes unstuck. If your vehicle has an electric fan, make sure it is coming on after a few moments. If it isn't, check that its fuse is OK, that the wire connections are solid, then check that the fan relay is not burned out. A heat sensor sending unit which controls activation of the electric fan could also have failed. In some 60's vintage vehicles, one could often stop overheating by replacing the stock 4-bladed fan with a 5-bladed fan. If you have an automatic transmission that is routed through your cooling system, and you've tried everything possible to correct overheating, your tranny may be on its way out. The problems your tranny may be having having operating normally could be effecting the engine temp. I agree with the changeing of the thermostat , Here is one more sug your radiator cap is not maintaining proper pressure get it pressure tested IF YOU DIDN'T CHANGE THE RADIATOR CAP WHEN DOING ALL THAT OTHER STUFF, GO AHEAD AND CHANGE IT. IF THE OLD ONE IS BAD IT WON'T HOLD THE PROPER PRESSURE AND THE COOLANT CAN BOIL= OVERHEATING! patricklaw1957@Yahoo.com Check the fan to see if it's running. If the engine heats up and the fan isn't going, the fan motor is shot. If you have tried everything else and you are still having overheating problems you might have a bad head gasket. I didn't see what type of vehicle you were working on. I had a 1988 Dodge Caravan. I replaced everything in the cooling system including putting an oversized radiator in. The problem turned out to be a bad head gasket. I never observed any oil in the radiator. If the thermostat was replaced and water pump and radiator as you say then there are only a couple things that it can COMMONLY be.It always seems to me that people like to take out the engine before replacing the spark plugs.Take theese Words of advice(alot of people over analyze things)99 percent of the time it's the easy stuff!your problem is probably the radiator cap.If it is not holding the proper pressure it will overheat.cost is about 4.95. could be bad head gaskit