Internal combustion engines contain explosions, and explosions create heat—lots of it. This heat is kept in check by a cooling system that circulates fluid (except in older air-cooled vehicles) around the hottest parts. This cyclical system pushes the fluid past the hot metal components and out into the radiator, where it dissipates the collected heat into the cooler atmosphere.
Although engines are designed to deal with a certain amount of the generated heat, an inefficient or malfunctioning cooling system will allow too much to build up. If your motor is tuned to the knife-edge and the heat isn’t controlled you can end up with detonation, the engine oil will break down as it overheats, leading to lubrication issues, and all manner of other horrors could spell a noisy, smelly expensive death to your motor. Increasing the power of your engine requires upgrading of many of the car’s other components. And while it is obvious that a quicker ride requires better brakes, tires and suspension, the cooling system is often overlooked—many a massive workshop bill can testify to this sad fact.
To use a basic comparison, accepted wisdom says that in everyday life the human body requires around two liters of water per day. If you live in a particularly hot climate (say Arizona) you would want to add 25% (or half a liter) to that, or, if you partake in strenuous exercise you would also want to add half to three-quarters of a liter. Your engine is basically the same. In everyday use and in a moderate climate, as long as the fluid levels are well maintained your car’s OEM cooling system will be fine. If you live in Phoenix it will probably need topping up more often and if you drive ‘enthusiastically’ on a stock engine you’ll want to do the same. If you add some serious cash into the motor, you’ll need to seriously think about upgrading some parts.
It makes sense if you think about it. If you’re expecting 25% more power out of your engine, you can expect a similar increase in the heat load generated by the engine that is passed into the cooling system. But where do you start? Well, let’s look at the individual components. You get a radiator, a fan, a water pump, a thermostat, a few sensors, an overflow tank, coolant and a selection of hoses, belts and clamps to connect it all together. If you’ve got a turbocharged or supercharged engine you’ll likely have an intercooler as well. It’s a fairly simple setup, but let’s take them one at a time…
The most obvious cooling system constituent is the radiator—you know, that giant slab of metal that sits behind your car’s front grille. It consists of an outer frame that is bolted to the car’s chassis and rows and rows of tubes (the core) through which the coolant flows. Attached to the tubes are thousands of fins; these effectively increase the surface area. One way to upgrade the radiator is to get a larger one, but due to space constraints and the reluctance to add weight to the front of the car, this isn’t necessarily the solution. But don’t fear, there are ways of getting a more efficient radiator by increasing the surface area without greatly increasing its physical size—and also reducing weight into the bargain (a direct replacement alloy rad can save 5-8kg for most models).
Firstly, moving anything that sits between the radiator and the cooling airflow is a good move. So creating more space between the radiator and ancillaries like air conditioning condensers will expose more of its face to the cooling airflow, hence making it more efficient. More tubes and fins also increase the surface area that can transfer the heat to the surrounding air, so this is the way to go—with a word or two of caution attached. However, due to the law of diminishing returns, you can over-egg the addition of rows and fins to a radiator to the point where it becomes counter-productive and actually reduces your radiator’s performance. Any racing engineer will tell you that three or four rows of tubes in a core is probably optimum; any more and you risk slowing the coolant’s flow. This can result in laminar flow—slower moving fluids passing over each other like cards being shuffled in a deck—creating an insulating layer of coolant that actually retards the heat transfer.
In addition to this concern, adding fins is a good idea and the optimum for performance radiators is around 12-16 fins per inch; any more can place them too closely together, restricting the cooling airflow, making it less efficient and reducing heat transfer. Generally the most effective type of radiator fin is a louvered one, this turbulates the airflow and increases the cooling action. The downside is that louvered fins can become more easily clogged with dirt or debris that passes through the front grille, so they should be checked and carefully cleaned more often. Saying this, the benefits far outweigh the added hassle of occasionally having to clear the clogged debris.
To maximize the amount of cooling air fed to the radiator, cooling plates can channel this air directly to the rad. Not only do they increase the efficiency of the radiator by anywhere between 10-15%, they also look very cool in any engine bay. There are many top radiator manufacturers, including Koyorad, Mishimoto and Fluidyne, and any of their upgraded radiators, either OEM replacements or performance models, make up the first step to improving the cooling system for any performance machine.
A fan is mounted to the inside face of the radiator and serves to increase the volume of air moving past the radiator’s core. On some cars the fan is belt-driven from the engine, so runs all the time the engine is running; of course this creates parasitic losses which robs power that should be going to the wheels and giving you a few more horsepower and miles on your mpg count. With advances in coolant and engine efficiency, most fans are now electrically-operated and activated by a sensor that determines when your engine needs cooling; when you’re on the move at speed, your car’s front-end design means it shouldn’t need any additional cooling.
Upgraded high-flowing fans can flow a little bit better, and are often slimmer and more durable to reduce bulk in the bay that you may want to take up with other things. The fan is usually surrounded by a plastic shroud that ensures its cooling airflow doesn’t escape unnecessarily; more effective shaped shrouds can also aid the cause—and look cool.
The thermostat sits between the engine and the radiator and blocks the flow of coolant to the radiator until the engine has warmed up. Because running an engine hard when it’s cold can do just as much damage as overheating, the thermostat ensures the motor reaches optimum operating temperature as quickly as possible, reducing engine wear, clogging deposits and emissions. Your OEM thermostat opens when the wax starts to melt at around 80°C, and the coolant flows. This is an optimum for the everyday driver, but for the enthusiast like you and me with high horsepower aspirations or for those who live in hot regions, performance thermostats that open at a few degrees less (say 70-75°C) are beneficial as a safety valve to stop that engine-killing heat.
You’ve got lots of options for upgraded versions but make sure that anything you buy comes with the correct gaskets to provide a good seal. Another couple of words of caution: Given what we’ve just said, you might be tempted to think that if you’re on track or in a drag situation that removing the thermostat in its entirety is beneficial, right? NO! The complexities of modern computerized engine controls mean that not running a thermostat can trick the onboard computer into running the fuel mixture too rich as it will run the car as it were continually cold. As the temperature sensor measures the temperature of the coolant and not the engine block, as the coolant is circulating too quickly it won’t reach the correct temperature and won’t remove enough heat as it will only be in contact with the heated metal components for a much shorter time. So, while the gauge reads normal, the engine itself could well be overheating, leading to greater wear and tear, and the eventual warping or destruction of the components through stress.
Boyle’s Law states that as air is compressed it gets hotter, losing its density. This isn’t what you want for maximum power from any forced induction system, so the job of the intercooler is to cool the air (making it more dense) before it enters the intake. It sits in the airflow course between the turbocharger and the engine intake and will be of either the air-to-air or air-to-liquid type. The intercooler’s core (similar in design to a radiator core with finned tubes, described above) makes the air cooler and denser so more can be forced into the engine (hence, forced induction). When mixed with the correct amount of fuel and given a bigger spark this increases power compared to a non-intercooled motor.
A well-designed aftermarket intercooler will a strike the right balance of heat exchanging and airflow with thicker cores, more efficient fin structures (again, as covered with radiators) and/or more frontal area, a lighter-weight alloy construction, more efficient internal airflow and better quality piping. There are many quality intercooler manufacturers, including ARC, Blitz, GReddy, HKS and Spearco. You can pay anywhere from $500 up to $3000-4000 for a monster, race-spec front-mount intercooler (FMIC). FMICs are the optimum solution for direct contact to cooling air, however with open-mouth bumper designs, this also puts them in the firing line for debris and damage. To this end they can also be mounted either above or behind the radiator, depending on the cooling requirements of the engine and the boost levels of the forced induction system.
For high performance applications it is advisable to keep your motor’s oil at a consistent temperature as well. Oil coolers are separate, smaller radiators that maintain an optimal temperature, maximizing performance and prolonging the life of the internals by dissipating heat from hard-working motors. Mounted usually underneath a vehicle or to the side of the front bumper, wherever there is space and decent airflow, an oil cooler keeps your oil at a constant optimum between the ten-degree range of 82-92°C. Below this the oil isn’t doing it’s job effectively, outside this range and the fluid begins to break down, losing its lubricating and cooling properties.
Odds and Ends
Other benefits can be seen by upgrading your engine’s hoses and clamps. They can easily form the weak link in the cooling chain, and are worth paying attention to. OEM rubber hoses can bulge, perish and split over time and don’t always react very well to extreme temperature changes. Look in any tuned engine bay and you’ll see an array of polyester-reinforced, silicon hoses—often in a rainbow assortment of colors for the show fiend as well.
Silicone hoses are designed to operate over a wider temperature range than standard hoses, and will provide a more consistent coolant flow as well as last longer and look cooler. A full engine bay’s worth of oil and coolant hoses from a top manufacturer such as Samco (they supply many top race teams and OEM supercar manufacturers) as well as turbo hosing and induction hoses can be had from as little as $100. Shitty-looking clamps on those hoses will not only do your engine bay wrong, but standard mild steel items corrode over time as well in the harsh environment they have to live in. Stainless steel clips are always worth those few extra dollars of investment. While replacing the hoses and clamps, a replacement overflow tank finishes the job off nicely. The overflow tank serves as a reservoir for excess fluid in the system (remember, heat expands fluids) and replacement alloy jobs look cooler and provide a better seal for the system.
The Last Resort
Your temperature gauge starts to rise, turning the heater on full blast and opening the windows stems it slightly but something’s definitely not right. If you’ve been driving like a loon, pull over and give the car an hour or so to sort itself out and calm down. If you haven’t, it’s something more serious with the cooling system. The good news is that most cooling issues are relatively easy and inexpensive to fix if caught early.
If you’re handy with tools, once the car is cool take the cap off the expansion tank and radiator as the first investigations to be undertaken. If there’s no mayo in and around the cap there’s a good chance it’s not the head gasket. Check the fluid levels, if they’re low then top them up. If this doesn’t solve the problem, limp the car home and park it up. Once it’s cooled down, set it up on a flat, level surface, start the motor and leave it running. If it pisses fluid all over the driveway then chances are you’ve got a leaking hose or radiator—not a major issue. If nothing leaks out from underneath, watch the gauges. If they approach the red and the fan doesn’t kick in it’s probably a bad sensor. If you can replace this and it solves the problem then all is good. If not, the next thing to check is the thermostat.
This lives in the return hose that runs from the top of the motor back to the radiator. Make sure the engine is cool, remove the top hose and replace the thermostat. If it still continues to give you grief, the next step is to check the water pump. Make sure the belts are attached (if the car has them) and that everything is moving freely. New water pumps are easy to fit, if it’s beyond this it could be clogged or damaged radiator, so check the core and fins for anything obvious and as a last resort give the radiator a good flush through.
These are just a few of the basic troubleshooting tips to deal with overheating; if any of this scares you, drive your car (gently) to a local mechanic and get them to take a look. The good news is that most issues can be solved for a couple of hundred bucks.
Cool Parts Guide
While we can’t mention all the parts and companies that can aid your cooling system, we’ve compiled a list of cool goodies from some very respectable companies. Most of these companies offer a vehicle-special kit or part for your ride, so don’t be shy and hit them up.
What: External Oil Cooler
What: Aluminum Radiator
1. Who: Blackworks USA
What: Radiator Hose Kits
2. Who: Blackworks USA
What: Slim Fans
3. Who: Blox Racing
What: Electric Slim Fans
4. Who: Blox Racing
What: Aluminum Radiator
5. Who: CBRD
What: Aluminum Racing Radiator
6. Who: CSF
What: Aluminum Racing Radiator
7. Who: Cusco
What: Radiator Cooling Plate
8. Who: Cusco
What: High Pressure Radiator Cap
9. Who: Garrett
What: Intercooler Cores
10. Who: HKS
What: Low Temp Oil Cooler Thermostat
11. Who: Improved Racing
What: Oil Cooler Adapter For LS Swaps
12. Who: Koyorad
What: Aluminum Radiator
13. Who: Mishimoto
What: Mitsubishi Evo Intercooler
14. Who: Mishimoto
What: Hyundai Genesis Oil Cooler Kit
15. Who: Mishimoto
What: Nissan 350Z Radiator
16. Who: Mizu
What: Electric Fans
17. Who: Mizu
What: Aluminum Radiator
18. Who: Nippon
What: Low Temp Thermostat
19. Who: Samco
What: Silicone Hoses
20. Who: Spal
What: High Performance Fan
21. Who: Stillen
What: Nissan 370Z Oil Cooler Kit