The national cost for a radiator cap replacement with CarAdvise in 2024 is between $13 and $40 with an average of $21.

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What is a radiator cap and how does it work?

The radiator cap is a small device that is part of the cooling system on a vehicle. The cap seals off the top of the radiator. But it does more than seal the system. It also functions as a pressure relief valve that regulates the maximum pressure in the system.

An internal combustion engine generates a lot of heat during normal operation. To ensure that your engine operates within a designated heat range without overheating, engine coolant (also known as “antifreeze”) is circulated through the engine block. The coolant absorbs some of the heat, exits the engine, and travels through tiny tubes in the radiator. Air movement across these tubes and their associated cooling fins removes heat from the coolant before it returns to the engine to pick up more heat.

Coolant is able to remove heat more effectively because it is pressurized in the cooling system. The radiator cap ensures that the pressure is able to build without building too high.


How is a a Radiator Cap Replacement done?

Radiator cap replacement is perhaps the simplest service procedure related to the engine cooling system. That said, it can be dangerous or ineffective if not done properly. That is because coolant in the system is extremely hot when the engine is running. Radiator caps are also specific to your engine’s cooling system and are not interchangeable with other vehicles.

Once the correct part has been selected, a technician must allow the engine to cool for about a half an hour to prevent scalding from steaming hot coolant under pressure in the system. From there, the cap is carefully unscrewed (usually with a towel covering the cap) in order to relieve any residual pressure. The new cap is installed and tightened. On some vehicles, the radiator cap might be tricky to access.

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National average cost of a a Radiator Cap Replacement
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How do I know if my radiator cap needs to be replaced?

A radiator cap can be tested by a mechanic. But there are signs that the cap is bad that do not require testing. If your radiator cap is failing, you might notice one or more of the following symptoms:

The coolant is leaking because excess pressure is forcing the coolant out of the system

Your engine is overheating due to a loss of pressure through the cap or air in the system through a bad cap seal

The radiator hose collapses from a low pressure level or vacuum in the system

Coolant is boiling over or steam is coming from the engine compartment

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Other questions customers ask

Can I replace my own radiator cap?
Replacing a radiator cap is not particularly difficult. However, if done at the wrong time, it can be extremely dangerous. The coolant inside the engine cooling system is under pressure when the engine is running and for a considerable amount of time after it has been shut off. Removing a radiator cap while pressure remains in the system can cause a person severe scalding and burns from escaping coolant and steam. It is also important that the correct radiator cap for your particular vehicle be installed.
Are radiator caps universal?
Radiator caps are not universal. In fact, they come in a huge selection of shapes and sizes, each one unique to a specific vehicle make and model. And the various caps available also come with different pressure ratings for different applications.
How do I know which radiator cap to buy?
Your vehicle owner’s manual will likely publish the specific pressure rating needed for the radiator cap. It might also be printed on a label under the hood. Of course, the pressure rating does not describe the shape and size of the cap. Your best bet might be to purchase the correct cap from the manufacturer, or at least a reputable auto parts store. You can also have a trusted technician obtain the correct radiator cap for your car.

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