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Radiator Plugged

Temperature gauge is normal on cool days, but reads higher-than-normal on warm to hot days. Engine may overheat, especially when traveling uphill and when using A/C.

Faulty thermostat or plugged radiator. Coolant flow can be restricted internally or air flow blocked externally. Typically, thermostats cause an engine to run hotter than normal at all times. Radiators, on the other hand, can be more difficult to detect. When internal restrictions are present, there will often be temperature differences between the top and bottom of the radiator. Debris in the coolant will settle in the lower passages of the radiator, gradually plugging the coolant tubes until they are completely blocked. Especially is this true when stop-leak products are used. Cooling fans will generally run, but will have little effect as the radiator’s surface area has been effectively reduced. Internally plugged radiators can be detected using an infrared thermal pyrometer. Normally the top section will be significantly hotter while the lower section is relatively cool. A free-flowing new radiator, on the other hand, will have uniform temperatures on all surfaces.

For external blockage, clean the radiator fins. For internal, re-core or replace the radiator.


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