Radiator caps are essential for identifying coolant overflow and keeping your engine’s cooling system at ideal pressure and temperature, and your vehicle’s performance. This buying guide will assist in understanding the importance and function of radiator caps, their failures, types, and benefits and help you to purchase the correct radiator caps as per your vehicle’s requirement.
- What Does a Radiator Cap Do?
- Where is the Radiator Cap Located?
- What does a Radiator Cap Look Like?
2. How Does Radiator Cap Work?
3. What Type Of Radiator Cap Should I Choose?
4. How To Choose A Radiator Cap?
5. Which Brand Radiator Cap Should I Choose?
6. What Are The Symptoms Of A Failing Radiator Cap?
7. How Long Should the Radiator Cool Before Opening?
- What Happens if Radiator Cap Pressure is too High?
8. Can you Drive Without a Radiator Cap?
- When to Replace the Radiator Cap?
- How Long Do Radiator Caps Last?
1 What Is A Radiator Cap?
The radiator cap’s primary function is to raise the boiling point of the coolant, and prevent the air from entering the system, thus ensuring a pressurized cooling system in your vehicle so that it runs smoothly. The radiator cap provides the necessary seal for a pressurized system, preventing radiator coolant from over boiling.
What Does a Radiator Cap Do?
A radiator cap is a pressure valve that is part of the car’s cooling system. The radiator acts as a heat exchanger, transferring excess heat from the engine’s coolant fluid into the air. It is composed of tubes that carry the coolant fluid, a protective cap that’s actually a pressure valve and a tank on each side to catch the coolant fluid overflow. The tubes carrying the coolant fluid usually contain a turbulator, which agitates the fluid inside. This way, the coolant fluid is mixed together, cooling all the fluid evenly, and not just cooling the fluid that touches the sides of the tubes. When coolant fluid overheats, it expands, causing the fluid to become highly pressurized. When it enters the radiator, the pressure increases even more because it’s in an enclosed space. The radiator cap acts as a release valve set to open at the maximum pressure point. Usually this is set at a density of 15 pounds per square inch (psi). When the fluid pressure inside the radiator exceeds 15 psi, it forces the valve open, allowing heat to escape and excess coolant fluid to overflow into the tanks on either side of the radiator. Once the radiator cools down, the coolant fluid in the overflow tanks gets sucked back into the pump, continuing its route through the cooling system.
Where is the Radiator Cap Located?
The radiator cap is usually located on the top of the radiator, either on the left or right side, but sometimes in the middle of the radiator. It is important to note that accessing the radiator cap while the engine is still warm is dangerous, especially because the coolant is most likely above the boiling point of water.
What does a Radiator Cap Look Like?
A radiator cap is a small, round device that fits on top of the radiator. It is easily identifiable as a small cap with a pressure release valve. The exact location of the radiator cap may vary depending on the make and model of the car, but it is usually found near the center or towards one side of the radiator.
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2 How Does Radiator Cap Work?
There are several components in the radiator cap such as a pressure spring, vacuum valve, pressure relief valve, and upper and lower rubber seals that must work in harmony for the cap to function properly. The pressure relief valve with the rubber seal is held down by a spring that bears against the cap. The spring and valve are driven up as pressure builds, allowing air (and radiator coolant) to escape to the overflow. A vacuum occurs on the top of the radiator when the engine cools. The lightly loaded return valve and spring are forced open by atmospheric pressure, allowing air to be pulled back through the overflow and into the radiator. If an expansion tank is fitted, only liquid is expelled and drawn back through the overflow. The radiator thus remains permanently filled with coolant.
3 What Type Of Radiator Cap Should I Choose?
Based On Design
A. Double Seal (Recovery Caps)
The recovery radiator cap (double seal) in a sealed or recovery cooling system allows coolant to flow to and from the recovery or expansion tank. The expansion tank works similar to the radiator cap and enhances the capacity of the system by absorbing excess coolant and minimizing excess pressure in the engine cooling system.
B. Single Seal (Non-Recovery Caps)
There is no recovery or expansion tank in an open or non-recovery cooling system, the single seal radiator cap permits coolant to be released and air to be returned to the cooling system. The non-recovery cooling system requires regular coolant checks and refilling to avoid the system running dry.
Based On Material of Construction
Radiator caps can be manufactured either in metal or plastic material depending on the vehicle manufacturer’s specifications.
4 How To Choose A Radiator Cap?
The radiator cap is one of the key components of the cooling system and is available at very reasonable prices in the market. Getting your radiator cap replaced at regular intervals can save you from a coolant leak which can lead to engine overheating and thus reducing overall wear and tear on your cooling system. Radiator caps vary greatly in terms of features, forms, and sizes, so choosing the proper one for your car is critical. You can select the radiator caps based on the below-mentioned points:
Based On Pressure Rating
It is very important to learn about the appropriate pressure rating for your vehicle’s radiator cap. Depending on the model of your car, each cap is unique. The correct pressure rating for your car is usually specified in the manual. If the pressure rating is not specified in the owner’s manual, it will be beneath the hood on top of your previous radiator cap. If you can’t locate the pressure rating on your car’s coolant cap for any reason, check with a nearby auto parts store, dealership, or mechanic shop.
Based on Seal Type
Single seal radiator caps are used in the non-recovery cooling system and allow the coolant to be released and the air, whereas, a double seal radiator cap is used in the recovery cooling system allowing coolant to flow to and from the recovery or expansion tank. A non-recovery cooling system does not have a recovery or expansion tank.
5 Which Brand Radiator Cap Should I Choose?
Gates Radiator Caps
Gates manufactures OE quality radiator caps and cool control caps for your heavy-duty vehicle applications, with a selection of durable, wear-resistant radiator caps for automotive applications without coolant recovery systems. Their manufacturing facilities are well equipped with state-of-the-art equipment for R&D and testing purposes, ensuring excellent quality and customer satisfaction.
Features
- All Gates radiator caps are constructed of corrosion-resistant, heavy-gauge metal to assure long service life and accurate pressure control
- Covers a wide range of pressures
- Designed and manufactured to OE standards
- No adjustment is required for installation
- Engineered for precise pressure control
For more products, please refer to our Gates Radiator Caps section.
Motorad Radiator Caps
MotoRad radiator caps are designed and manufactured to offer precise pressure control for the automotive cooling system. They offer a wide range of options for your vehicle’s specific needs. MotoRad is one of the leading brands in the automotive aftermarket sector, and its products are crafted keeping customer satisfaction in mind.
Features
- Wide range of applications with radiator caps pressure ranging from 4 PSI to over 30 PSI
- Provides hassle-free installation
- Precisely designed and manufactured using premium quality materials that enhance durability
- Designed and manufactured to OE standards
For more products, please refer to our Motorad Radiator Caps section.
Mr. Gasket Radiator Caps
Mr. Gasket is one of the leading aftermarket brands that offer a wide range of products expertly crafted in their state-of-the-art manufacturing facilities. Their products comply with the industry standards and are meticulously designed with customers in mind.
Features
- Unique design provides trouble-free installation
- Displays the coolant temperature and help tells you exactly when the radiator coolant temperature is low enough to safely open the radiator cap
- Compatible with virtually all domestic vehicles
- Engineered for precise pressure control
- Designed and manufactured to OE standards
For more products, please refer to our Mr. Gasket Radiator Caps section.
6 What Are the Symptoms of a Failing Radiator Cap?
Even in normal operation, combustion engines create a lot of heat. If heat is not removed from the vehicle’s engine, there will be cooling system failure leading to catastrophic engine failure. A damaged radiator cap is a common cause of cooling system failure. Knowing when to replace a radiator cap is simple once you understand the below-mentioned warning signs:
Coolant Leak
If the pressure holding capacity of your vehicle’s radiator cap is less than what it was designed for, then it may be a prime cause for leakage, especially if it causes an old coolant hose to fail. It may also occur when the system reaches the target pressure, and the radiator cap may fail to allow excess pressure to leak into the coolant reservoir. Moreover, if the system is overpressurized, the weakest point will leak coolant because substances inherently seek the path of least resistance. These leaks may appear only at operational temperature or after a period of driving. You may observe a leak pouring from a coolant line into the engine compartment, or even straight up into the air because the system is pressurized.
Overheating Engine
An inadequate seal (such as one in a defective radiator cap) can introduce air pockets in the cooling system leading to inappropriate pressure in the cooling system, which causes the engine to overheat. This reduces the coolant’s boiling point, preventing it from absorbing enough heat from the engine. When the radiator coolant boils, it forms gas due to evaporation, similar to the steam. If your vehicle’s engine starts to billow steam, it is because the coolant is boiling and escaping via a faulty seal on your radiator cap. This will ultimately lead to engine overheating, and if neglected for a long time, it may permanently damage the engine.
Damaged Radiator Hose
Internal pressure variations can cause hoses to distort or tear. When the pressure drops too low, a vacuum effect occurs, causing one or more hoses to collapse. Extremely high pressures can also cause line cracks. Investigate that no hoses are hard or spongy when inspecting the cooling system. Hard hoses are brittle and can’t take too much abuse before cracking under pressure, whereas spongy hoses are weak and may collapse.
Low Coolant
You may have a problem if you notice that your coolant level is falling. This may be due to overheated coolant escaping the system as vapour through the damaged radiator cap. Never allow the coolant to drop below the required amount. A low mark on the coolant reservoir usually indicates this. In a pinch, you can top off the coolant level with distilled water until you can refill it with actual coolant, as the mineral-containing water may damage the cooling system.
Coolant Overflow
When the radiator cap fails, the coolant may flow into the reservoir tank without the usual trigger of excess pressure. This implies that as the coolant expands, it flows into the reservoir tank. The pressure lifts the cap, allowing the coolant to flow to the overflow tank. The coolant will be released too quickly if the cap is damaged, causing the reservoir to overflow.
7 How Long Should the Radiator Cool Before Opening?
It is recommended to wait at least 1-2 hours for the engine to cool down before attempting to open the radiator cap. However, the actual time required for the engine to cool down depends on various factors such as the ambient temperature, the size of the engine, and the duration of the drive.
If you need to work on the radiator, it’s best to wait for the engine to cool down completely. If you’re in a hurry, you can check the hoses and radiator to see if they are comfortable to touch. If they are too hot to touch, give them some more time.
What Happens if Radiator Cap Pressure is too High?
If the radiator cap pressure is too high, it can cause damage to the cooling system and lead to coolant leaks or engine overheating. When the pressure in the radiator exceeds the recommended levels, it can result in a blown radiator hose or even a cracked radiator. The excess pressure can also cause the coolant to boil at a lower temperature, leading to overheating issues. It is important to regularly check the radiator cap and ensure that it is functioning properly to prevent these issues.
8 Can you Drive Without a Radiator Cap?
Technically, you can drive without a radiator cap, but it is not recommended. The radiator cap plays a critical role in stabilizing the coolant in your car’s engine. The high temperatures of the engine often cause bubbles to develop within the coolant system. With the cap well fitted on the radiator, these bubbles are confined within the engine, and the coolant can move easily. But when you take the radiator cap out of the equation, the bubbles will push the coolant out of the radiator neck in massive burps. This will result in loss of coolant, which can lead to damage to the gasket resulting in leaks. Running an engine without a radiator cap will mark the beginning of engine issues that won’t be easy to remedy.
When to Replace the Radiator Cap?
Knowing when to replace a radiator cap is important to ensure that your car’s cooling system is functioning properly. Here are some signs that indicate it’s time to replace your radiator cap:
- Coolant leaks: If you notice coolant leaks under the radiator, it could be a sign that the radiator cap is not sealing properly.
- Overheating: A bad radiator cap can cause the engine to overheat, which can lead to serious damage.
- Low coolant levels: If you notice that the coolant level is low, it could be a sign that the radiator cap is not holding pressure properly.
- Radiator cap is damaged: If the radiator cap is visibly damaged or corroded, it’s time to replace it.
It is important to replace the radiator cap with one that matches the factory specification. Each radiator cap is rated for a certain amount of pressure it can hold, and different cooling systems call for different pressures.
How Long Do Radiator Caps Last?
The lifespan of a radiator cap depends on various factors such as the type of cap and the conditions it’s exposed to. Typically, radiator caps last anywhere from 3 to 7 years . If you notice any signs of wear or corrosion, it’s probably time to replace the cap
