Should I Put Coolant in My Radiator Or Reservoir?

Coolant and antifreeze are often interchanged by automotive professionals; however, technically the latter refers to any product pre-mixed with water (known as coolant) while pure ethylene or propylene glycol-based antifreeze does not contain any water at all.

When adding engine coolant, the best approach is typically pouring the product directly into the radiator. This helps avoid mixing different types of coolant together while assuring you add enough to meet requirements.


Your radiator serves as the heat exchanger that controls engine temperature in your car, keeping its coolant fluid at an optimum level for engine operation. However, it needs help from engine coolant (commonly referred to as antifreeze). If additional engine coolant needs to be added into your system then be sure to add it via the radiator.

Your coolant system is essential in protecting your car from overheating, potentially leading to costly damage. Coolant flows through your radiator before being circulated through your engine block and head to collect excess heat that could otherwise melt engine components. After cooling in the radiator it flows back out through air blowing through its front grille for further cooling before returning into circulation – repeating its cooling cycle once again!

If the coolant levels in your radiator tank have decreased, refill it by mixing equal parts engine coolant and water. Before making this refilling effort, ensure the engine is cold as this will ensure proper circulation of coolant throughout its system. It is also important to monitor its levels as they will decrease over time due to evaporation and engine use.

Your radiator should accommodate for this option, provided its design permits. Modern cars often feature radiators situated towards the front, with separate coolant reservoirs located elsewhere on board.

As a general guideline, adding coolant directly into the radiator is ideal as this removes any risk of overfilling the reservoir. If using a coolant reservoir instead of your radiator to replenish levels, take note that hot temperatures cause expansion which limits how much coolant can be added at once.

Having difficulty keeping the coolant levels of your vehicle consistent could be an indication of an underlying problem with its cooling system, such as cracks in its radiator, hoses or water pump – it would be prudent to bring your vehicle in for service immediately in such cases.


A radiator is an essential component of your engine’s cooling system, transferring engine heat directly into coolant to lower its temperature and prevent overheating. But for maximum effectiveness, regular checks on coolant levels and replenishment as required is key to its function.

Not only does your car engine come equipped with a radiator, but also an overflow tank to store liquid expansion when temperatures increase. The overflow tank’s cap usually features minimum and maximum markings to indicate appropriate fill levels; for instance “L” could denote low levels while “F” signifies full levels – both lines should be visible at normal operating temperatures of your coolant system.

Antifreeze and water should always be mixed evenly when topping up your car’s coolant, to reduce risk from engine block overheating and prevent premature engine block wear and tear. If you do not have pre-mixed coolants on hand, it is easy to make up a mixture yourself by mixing equal parts distilled water and antifreeze into equal proportions.

If you’re uncertain of which coolant is appropriate for your vehicle, referring to your owner’s manual is often the best solution. A long-life product which contains both antifreeze and corrosion inhibitor should be selected; additionally it should have low viscosity so as to allow easy flow throughout radiator and overflow tank systems.

To refill your coolant, open up the reservoir tank’s cap when your engine is cold, using a cloth to protect yourself against burns, and take steps to unlatch its seal. Pour enough coolant to reach its maximum level on the reservoir without overfilling as expanding warm air can expand your mixture, potentially leading to leaks.

Mixing Coolant Types

There are various coolant types on the market, each designed for specific functions. When conducting DIY coolant refills yourself, it’s crucial that you use only the appropriate antifreeze for your car’s specific model and usage type – mixing different coolants together may reduce effectiveness of corrosion inhibitor and potentially endanger its safety. Consulting either your owner’s manual or auto technicians should reveal which coolant type best meets the requirements of your vehicle.

Your engine could overheat without sufficient coolant to maintain an ideal operating temperature. Coolant absorbs heat as it circulates and transfers it to radiators or engine hoses for dissipation, maintaining temperature stability under various climate conditions.

Your vehicle’s coolant is composed of a mixture of half ethylene glycol and half water to protect its fluid from freezing in cold weather conditions and turn into steam, while also raising its boiling point to operate effectively in extreme heat. While pure water might work for racing cars, for most vehicles coolant/antifreeze is much better at transferring and holding heat than straight water; additionally it protects metal components of both your engine and radiator from corrosion.

Coolant can be purchased from most automotive parts stores, but for optimal performance it is always wise to consult your owner’s manual or professional auto technicians in order to identify the ideal type of antifreeze for your vehicle. Selecting an incorrect mixture could prove just as harmful. It’s also crucial that before adding any fresh coolant it be checked that there is enough space in your reservoir before overfilling as overfilling will damage its cooling system and could render it inoperable.

If the reservoir of coolant is empty or malfunctioning improperly, you can pour directly into your radiator by opening up its cap first to allow air bubbles to escape and prevent it from overfilling your radiator. Be mindful that this could cause it overflow!

Adding Coolant

Coolant is a water-based liquid used to prevent engines from overheating by regulating temperature. An engine’s production of energy, whether for powering the vehicle or heat generation, must be managed so it doesn’t overheat and break down. Coolant runs through passages of an engine to absorb some of this heat before being sent through passageways of its radiator to be cooled by air flow; then back through passageways back to continue cooling its temperature in check before being sent back into circulation again for repeating this cycle and keeping temperature under control.

Although water may work in an emergency situation to top off your radiator’s coolant levels, using antifreeze is usually best as it prevents corrosion that could otherwise harm the engine. Your owner’s manual should provide guidance as you select the optimal blend for your vehicle.

Vehicle radiators contain special tanks designed to store coolant, usually transparent containers that feature minimum and maximum lines on their side. When adding coolant to this reservoir, add until it reaches maximum line to prevent engine overheating, which can result in costly and possibly permanent damages to your car.

Before opening your radiator cap when the engine is hot, wait for it to cool before adding coolant. Alternatively, if time is short, use an expansion/overflow tank instead.

Once you find the coolant tank under your hood, its cap should be easily opened by hand. For assistance in finding this part of your vehicle, refer to your owner’s manual for help. Upon finding this part of your coolant system, be sure to take extreme precautions with the coolant cap, such as wearing gloves and long-sleeved shirt in case any of its contents escape unexpectedly and cause burns or disfigurement.

Coolant can occasionally enter a vehicle’s electrical system and short out wires if its fluid levels become excessive, but such instances are rare. Vehicle wiring was never intended to be exposed to this fluid and its presence may prevent starting of your car or lead to malfunctions such as headlights, brake lights, battery, radio etc.