The radiator cap is more important than most people realize.
An often overlooked radiator cap is a cause of engine overheating.
A radiator cap sounds simple, but it's essential to the proper functioning of the cooling system.
A faulty radiator cap can cause engine overheating, loss of coolant, or severe engine damage.
Therefore, pressurized cooling systems help prevent overheating and loss of coolant.
It also raises the boiling point of the coolant by approximately 3 degrees Fahrenheit for each additional psi above atmospheric pressure.
As the engine warms up and the coolant expands, it becomes pressurized. Cap pressure relief valve allows pressure to build up to a set level, then allows excess pressure to escape.
High pressure radiator cap
Radiator shrouds also act as pressure relief valves. They will avoid excessive pressure. Uncontrolled high pressure can damage the radiator, heater core, hoses or water pump seal. The pressure cap also prevents the radiator and reservoir hoses from collapsing. When the engine cools down, it creates a vacuum in the cooling system. This vacuum draws refrigerant into the system instead of air.
Always check the cover during routine maintenance. Never remove the plug when the engine is hot. With the engine off, place a rag over the cover and remove it. Turn it counterclockwise about 1/4 turn until it hits the safety stop. Allow all pressure to release before removing the cap by pressing down and twisting counter-clockwise.
5 Common Signs of a Bad Radiator Cap
There are certain signs that will let you know if you have a faulty plug:
Coolant is leaking
If the radiator cap is stuck, the fluid cannot be released. This will cause pressure to build up inside the radiator, causing the hose to leak or open. If you notice coolant near the radiator or radiator cap, you obviously have a coolant leak. Check if the cooler has any holes or if the cover looks worn or damaged. If so, replace the cover.
Overflow tank
Coolant enters the reservoir tank as it expands. The plug is released by the pressure and the coolant is sent to the overflow tank. If you have a bad cap, the coolant will leak out too quickly and cause the tank to boil.
The coolant hose is collapsing
You may have a bad plug if the coolant hose has collapsed. The vacuum will not release properly and this will cause the coolant hose to sag during the cool down period. If this happens, check the cover for damage. If there is, replace it immediately.
Air inside the cooling system
When the cap is not closed properly, air enters the cooling system. This will create air pockets inside the heater core, thermostat and radiator hoses. As a result, the engine will start to overheat because it cannot withstand a constant temperature.
Motor overheats
A coolant or air leak in the cooling system can cause the engine to overheat. If you notice your car's engine overheating, don't look under the hood unless you've turned off the engine. This way the engine can stay cool while it is being checked. If there is coolant near the radiator cap, the pressure cap may be damaged. Check and replace if necessary.
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