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Engines generate high amounts of heat from the constant combustion of fuel. Though hot exhaust gas does exit through the vehicle’s exhaust system, the engine block itself absorbs much of the heat. Keeping all the components from reaching a dangerously high temperature is the engine’s cooling system, the largest and most visible part of which, is the radiator.

What is the Radiator?

A radiator is a cooling device used to dissipate heat away from the engine block. It is key to the engine’s cooling system. The main objective of the radiator is to carry heat from the engine by convection, using a specially formulated engine coolant. Radiators were originally made of brass and copper, but modern radiators also utilize aluminum and plastic. Located in the engine compartment, the radiator is commonly located in front of the engine block and the radiator cooling fan.

, How to Replace a Damaged  Radiator
Coolant leak in the radiator could cause your engine to overheat.

A car’s radiator is basically a heat exchanger through which the coolant circulates. Heat travels in three ways: conduction, convection, and radiation.

The heat from the cylinder heads (the hottest cooled component) and the cylinder walls is absorbed via conduction) by the coolant the water pump circulates through the engine’s “water jacket.” Before the thermostat opens, the coolant “bypasses” the radiator and travels through the heater core for early cabin heating (this is “convection,” which is the transfer of heat by movement of the coolant that absorbed that heat via conduction).

But when the thermostat opens, most of the coolant begins to circulate through the radiator, which is a series of tubes separated by fins. The heat from the coolant is conducted to the tubes and then to the fins, and the radiator is mounted so that air passes through the fins, and the heat is carried or “conveyed” away (convection) so that the coolant leaves the radiator much cooler than when it entered the radiator

How does a Radiator work?

An exploded view of a radiator will show the radiator core assembly, cooling fins, inlet and outlet pipe and tank, and a pressure or radiator cap. The radiator core is a set of thin tubes made of brass or aluminum spanning the radiator frame. Cooling fins made of coiled copper strips, sandwich the radiator core, which rejects heat from the liquid running through it.

Inlet and outlet pipes deliver hot liquid from the engine to the radiator, and in turn, returns cooled liquid to the engine block. Hot fluid inside the radiator expands, building pressure within the radiator. At maximum pressure, the spring-loaded pressure cap opens and hot coolant escapes to the overflow tube, keeping the radiator within at optimum operating pressure.

Coolant v. Water

Engine coolant and antifreeze are specially formulated liquids poured into the radiator and the coolant reservoir. Though water can be used in place of coolant or antifreeze, the probability of water boiling during summer or freezing during winter is high. In addition, water is corrosive and can clog the radiator with rust over time. Made of ethylene glycol, coolant and antifreeze have higher boiling temperatures and lower freezing temperatures. This gives the liquid higher heat absorption, letting the cooling system run efficiently. Antifreeze and coolant can also protect your radiator with anti-corrosive additives.

Heat transfer by convection is the act of carrying heat away from a source by a liquid. The transfer of heat then cools the source. In a vehicle, coolant is flowed through the water pump into the engine block, collecting heat produced by the cylinders and the combustion chambers. The coolant then flows out the engine into the radiator through the inlet pipe and gets collected in the inlet tank. Coolant makes its way through the radiator core, getting cooled by the air flowing through the cooling fins.

Fresh coolant re-enters the engine through the water pump, then repeats the whole process. During standstill, the radiator fan turns on, sucking air through the radiator, simulating flowing air through the cooling fins. Internal combustion engines in our vehicles need to be kept cool to avoid overheating. Once an engine overheats, various components fail and a domino effect of damages occur.

, How to Replace a Damaged  Radiator
The radiator is a cooling device that dissipates heat away from the engine block. It’s a critical part of the engine’s cooling system.

What Goes Wrong with Radiators?

The simplest of problems can cause havoc to your radiator, and in turn, cause your vehicle to overheat. Pressure in the radiator, along with the high operating temperature can cause a substandard radiator to crack at the welds or damage its plastic components. This can give the coolant an avenue to leak, which will eventually empty the contents of the radiator and the coolant reservoir.

Factors such as old, cracked hoses and loose hose clips will also cause leaking, depriving the engine with sufficient cooling liquid. Corrosion from sitting water may clog the radiator core, leading to a defective radiator. In major cases, damage to the cooling fins can deem a radiator defective. Exposed for maximum exposure to flowing air, cooling fins can be easily deformed by hand, or by tools accidentally dropping on the radiator.

If the cooling fins are deformed or broken off the radiator, air cannot pass through which will then cause the hot coolant to return back into the engine. Radiator caps that are loose, or not tightened properly, will also cause the coolant to gush out. Lastly, a stripped or improperly screwed drain plug can also cause the radiator to leak.

Prevention is the greatest defense to overheating problems, and an inspection of the radiator will go a long way. Ensure the cooling fins are in proper condition, and that none have been bent back to close the flow of air. Look for signs of leaking underneath the vehicle and around the radiator as the vehicle idles. Give hoses connecting to the radiator a quick squeeze, checking their elasticity.

While you’re at it, include a quick check of the hose clips to make sure that they are still fastened down properly. If the hoses give, or cracks start to form, it is a sign that they need to be replaced. Once the vehicle is shut off, listen for the sound of coolant back flowing into the coolant reservoir. This is a sign that the radiator may be clogged by rust or other particles which have built up through time. Unscrew the cap, and check if the coolant inside the radiator is turning brown, or is contaminated. Brown coolant is a sign of corrosion within the radiator core.

Return the radiator cap, making sure to latch it down properly. Radiator caps typically lock in place, if aligned properly with the filler neck. Reach down to the drain plug, and make sure that there are no leaks around the plug and that it is screwed in properly.

Repair or Replace?

The function of the radiator is extremely important. This is why when it is damaged the solution you choose will directly affect the overall longevity of the vehicle. Movies have popularized cracking an egg into the radiator as a way to stop a leak. The logic to this is that the egg will seal the leak as it cooks solid. Although it does work, on occasion, it is not advised as it can cause build-up that can eventually clog more than just the radiator. Instead, simple leaks can be easily fixed with sealants. Take note, however, that this is only a temporary fix to give you enough time to drive to a mechanic.

The recommendation, regardless if it is a small or large damage, is to replace it. This is not a ploy to get you to spend on a new radiator, but the only reliable solution to preserve the life of the vehicle. Radiators range from $90-$400 depending on the vehicle, radiator material, and size. Having a trusted mechanic install a radiator will add $90-$120 to the mix.

If you’re mechanically inclined, installing a radiator at home is simple and can cut costs significantly.


  1. Twist off the radiator cap, drain plug of the radiator, to completely drain the coolant.
    Note: Coolant may be harmful to animals and vegetation. Do not expel it straight into the ground or down the drain. Coolant can be properly disposed of at your local recycling centers.
  2. Identify the inlet and outlet hose, along with the backflow hose. Loosen hose clamp with pliers, and disconnect hoses. Note: There will be coolant also stored in these hoses, have a bucket ready to also catch the remaining liquid. Automatic vehicles will also have transmission cooler lines, which need to be disconnected also. Be aware of ATF that may leak from the removed lines.
  3. Disconnect the negative battery contact. Undo all the bolts attaching the radiator to the vehicle with a ratchet wrench, and lift out of engine compartment. Note: Some vehicles have the radiator fan attached to the radiator assembly, while others will be attached to the engine. Be aware that radiator fans attached to the radiator assembly have electric lines, which need to be disconnected before lifting the radiator assembly.
  4. Transplant all attached components from the old radiator, to the new radiator.
  5. Place new radiator into the engine compartment, reattaching the electrical line for the radiator fans. Secure radiator assembly in place by attaching, and tightening all bolts used.
  6. Reattach the transmission cooler lines, and hoses, with respective hose clamps. Note: Consider replacing all hoses attached to the radiator, as preventive maintenance.
  7. Begin to refill the radiator with fresh coolant. When radiator refuses to accept coolant, turn the engine on, along with the heater, so fresh coolant reaches the heater core. Once the radiator is already full, seal radiator with the radiator cap, and fill coolant reservoir.
mechanic checking car's coolant
Check the quality of the coolant in the radiator. A simple look under the radiator cap will reveal tell-tale signs of a corroding radiator.

Beyond Stock Radiators

Performance vehicles operate at higher levels than the typical daily driver. Engines in performance vehicles produce more heat to increase their performance. Larger radiators are fitted to accommodate the additional heat transfer needed. Aftermarket racing radiators are available for purchase and can be ordered to specification. Cooling a higher performing engine faster will help it produce horsepower, and run efficiently. Consider the space in your engine compartment, along with the anchor points for your radiator. Asking questions such as, “will modifications to current anchor points or even additional drilling of anchor points be needed to an aftermarket radiator?” is important. In addition, the width, and thickness also greatly affect the efficiency of the radiator. The larger the surface area also needs the greater flow of air. Larger fans or grilles complement the installation of a larger radiator.

Special cases like rallycross vehicles have radiators the size of the rear compartment. These vehicles are capable of gunning 0-60 mph in less than 2 seconds while running a 2 Litre turbo engine. This level of performance produces a lot of stress and heat inside the small displacement engine, which is why it requires a larger radiator. The key to running the radiator in the rear is keeping it clear of mud and debris during a rallycross race. In addition, rallycross involves a lot of contact between vehicles, placing the radiator in the rear compartment avoids having to replace it after every run. Airflow over the body will still lead cool air to the radiator, even if it’s in the rear of the vehicle.

Keeping it Cool

When purchasing a used vehicle, check the quality of the coolant in the radiator. A simple look under the radiator cap will reveal tell-tale signs of a corroding radiator. During the test drive, be sure to keep an eye on the temperature gauge, which should rest at the middle of the indicator. If you have a brand new vehicle, make sure to change the coolant every 3-5 months, or change to antifreeze before winter. It isn’t too late if the radiator coolant in your vehicle hasn’t been changed in a while. Simply flush out the old coolant with water multiple times until the liquid draining out the radiator is clear of gunk and debris. Be sure to refill the system with fresh coolant after. Check the owner’s manual for the correct amount of coolant needed. Keep your engine cool and running efficiently by keeping your radiator in good condition.

Products Mentioned in this Guide

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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