Cooling fins in radiator are dirty. Spray through the radiator with a garden hose so you can see light between the cooling fins. Air must pass through the radiator to dissapate the heat.(fans draw air in.)|||Water pump?|||Low fluid level in radiator|||There may be coolant leak, leading to insufficient amount of coolant. My car had that problem, They replaced that pipe with gasket and it became all right.|||Check your radiator fluids. It sounds to me like the water pump is going out or is already gone.
What kind of and year of vehicle?|||Check for a leak in the radiator. Also, could be the sensor that turns the fan on when the car is in idle. The fan new cars do not come on until the temperature reaches a certain point.
See if you have a water spot under the car after it has been turned off for a while. If you do, then the Water Pump is a very likely problem.|||It could be many things. You say the fans are working. Is the car overheating when the fan is running? Does the car stay at proper temp when you are driving it?
Some cars have to have the air released (bled) from the cooling system. It couls also be a clogged radiator. More infomation is needed to be of any more help.|||If you have the proper amount of coolant and the radiator cap is good, I would suspect the radiator core is partially clogged.
When you are moving the air passing through the radiator helps to dissipate the heat. The next time it occurs turn the heater and the fan on full. This basically adds about a gallon to your cooling capacity and also dissipates the heat. Did the temperature drop?
Any good radiator shop should be able to analyze this.
