There are many myths and misconceptions about engine cooling, but the truth is your engine’s cooling system must perform a balancing act. It needs to extract enough heat to keep your engine happy, yet maintain enough heat to keep it operating efficiently. That means keeping the engine in the 180- to 210-degree F range.
To achieve and maintain optimum temperature range, a good cooling system needs the right-sized radiator and fan combo. It must also have the appropriate water pump speed and coolant flow between the engine and radiator.
Typically, when engines overheat or run too cool, it’s because of these cooling systems myths and misconceptions. Here are some of the more common myths and mistakes and why you should avoid them.
Eliminating the Thermostat
One of the greatest — or perhaps worst — cooling system myths is that you can remove your thermostat to eliminate overheating. This will only add insult to injury! When coolant never has a chance to give up heat via the radiator, it gets hotter and hotter, especially if you’re stuck in traffic. And even on the open road, coolant never has a chance to park in the radiator long enough to give up heat energy to the atmosphere.
Never operate your engine without a thermostat!
Thermostat selection boils down to application. Although enthusiasts tend to choose a 160-degree F thermostat to treat overheating issues, the 160-degree thermostat was originally intended for alcohol antifreeze back in the day. The best thermostat for classic vehicle applications today is the 180-degree thermostat. If you’re experiencing overheating with a 180, you have deeper problems with other components. Late-model computer-controlled vehicles mandate the use of a 192- to 195-degree F thermostat.
Water is the Best Coolant
Another myth is that water is the best coolant.
This is true in terms of heat conduction; however, it is also the best source of corrosion. If you are using straight water, you should always add water pump lubricant and a corrosion inhibitor. Also, use a coolant enhancer like Water Wetter, which improves surface tension and heat conductivity.
Coolant manufacturers often suggest a 50/50 mix of ethylene glycol and water, which will protect your cooling system down to -34F. If you’re expecting temperatures colder than that, you need a block heater or a warm garage. Mark Jeffrey of Trans Am Racing in Southern California tells us he runs 100-percent ethylene glycol and no water without consequence and has been doing it for many years. His logic is coolant temperature runs only marginally higher and this approach eliminates any risk of corrosion.
If you opt for the 50/50 mix, you can buy antifreeze already mixed with water for the sake of convenience. If you’re going to run an ethylene glycol and water mix, it is suggested you run distilled water to keep minerals out of your cooling system.
Summit Racing offers you another coolant option known as Evans High Performance waterless coolant. This is the last coolant you will ever have to buy because it is permanent. You run 100-percent of it in your vehicle’s cooling system. Begin your Evans regiment with new hoses and cooling system components and a system that is bone dry. If you’re servicing a system with traces of ethylene glycol and water, the Evans Coolant Conversion Kit is the best way to get started.
Improper Coolant Filling
We’ve seen a lot of people either under-service or over-service coolant.
When you are servicing a cold engine, you should add coolant to one inch below the filler neck which allows for expansion as the engine warms. Coolant can rise as much as one inch as the engine warms up. Start your engine with the radiator cap removed and coolant one inch below the neck. Then, observe as the engine warms. Allow time for the thermostat to open and for the engine to burp any stray air pockets.
No Anti-Collapse Spring
There are those, including hose manufacturers, who believe you don’t need an anti-collapse spring in the lower radiator hose. The truth is, you must have an anti-collapse spring in the lower radiator hose if you have an older vehicle with a conventional cooling system.
Because the lower radiator hose channels coolant to the water pump and engine, it is susceptible to negative pressure and collapse at high rpm. The anti-collapse spring prevents that from happening. One hose manufacturer says you don’t need the anti-collapse spring because it was used only for factory-fill purposes. This has never been true because of the positive pressure on the lower hose during fill.
Always run an anti-collapse spring in the lower radiator hose.
A Faster Fan is a Better Fan
There are many myths regarding electric fans. One belief is the faster a fan turns, the better — which is not completely true. At high speed, the radiator slipstream should be strong enough to carry heat from the radiator. When air is moving too fast, you get into boundary layer issues where heat doesn’t get carried away because air isn’t actually touching fins and tubes.
You want air to move slowly enough across fins and tubes to where it carries heat away. At speeds above 40 miles per hour your engine doesn’t need a cooling fan. This is why a thermostatic clutch fan or electric fan works best.
More Fans are Better
Some folks believe more fans are better. But that isn’t completely true, either. You don’t really need a fan both behind and in front of the radiator. Ideally, you will have a fan behind the radiator that provides cooling capacity based on coolant temperature. If your vehicle needs two cooling fans, there’s a deeper problem than fan capacity.
Improper Fan Spacing and Shrouding
One rule we see broken time and time again is fan spacing and shrouding. In most cases, cooling fans should be shrouded for proper vectoring of air velocity through the radiator. We recommend you pay close attention to what the factory does in any application.
Overlooking the Radiator Cap
Your coolant is under pressure to keep the boiling point as high as possible. That’s why you you want the highest pressure cap rating suitable for your application. Caps for older vehicles should be rated for 7-12 pounds; newer vehicles should have radiator caps rated to 12-18 pounds.
Cheap is Cool
It’s cliché, but you get what you pay for. When replacing cooling system components such as hoses, the water pump, and thermostat, don’t do it on the cheap. Spend good money on the best components and sleep better. Goodyear Super Hi-Miler cooling system hoses last longer than your average off-the-shelf hose, especially when paired with high-quality worm gear clamps.
You can find a wide variety of water pumps for nearly every application imaginable. Regardless of what brand of pump you choose, always opt for a high-flow water pump and be mindful of pulley ratio (pump speed).
Now that you know what pitfalls to avoid, scroll through the slideshow below for some valuable tips on choosing cooling system components.