The radiator cap is an integral part of a vehicle’s temperature control. This serves several purposes: it seals the cooling system from debris and contaminants, maintains a constant pressure and boiling point, and allows the coolant to reach the radiator. A bad cover can cause a number of problems; learn how to identify one and replace it to avoid overheating problems.
Low coolant levels
Most vehicles have a warning light that indicates low coolant levels. If you have recently topped up the coolant feed and the light persists, the coolant may boil out prematurely and overflow the radiator expansion tank. This is a sign of a failed pressure seal in the radiator cap.
Collapsed radiator hoses
If you notice that the hoses connected to your vehicle’s radiator are flattening and kinking, this is a sign of a failed return seal in the radiator cap. This seal allows the flow of the coolant to return to the radiator once the engine has cooled down, and a vacuum can be created if the flow is impeded.
Reheating at low temperatures
An overheated engine in relatively cold weather is the most common sign of a bad radiator cap. The main seal, which creates a joint between the cap and the radiator filler neck, can be eroded or poorly assembled, allowing tank depressurization and a reduced boiling point.
