Cooling Off - Cooling System Upgrade for Fifth Gen Honda Civic

If you've read our tech long enough, you would know that making horsepower can sometimes be a tricky business. It's a balancing act of air, fuel, and spark that can amaze in its potential to both create and destroy. Indeed, pushing the power envelope is a good way to take engines and engine parts to the ragged edge, but luckily there are methods of insurance.

One of the easiest, particularly for owners of older Hondas, is to upgrade the cooling system by replacing the factory copper/brass radiator with an aluminum one. Since making lots of power will likely increase an engine's thermal load, a wider, more efficient, three-row aluminum heat exchanger will help counter the increase in load. In addition to better cooling, which equates to reliability, the aluminum units also weigh less.

To illustrate how simple a radiator swap is, coworker Michael Arpon photographed his '95 Civic Si hatchback as it received a Koyo Cooling replacement from Pro Street Import in La Mirada, Calif. The daily driver has already been upgraded with a B18C5 swap that currently puts out 195hp and 135 lb-ft of torque on the Dynojet, and Arpon hopes to take that horsepower number well above 200 some day. Arpon also secured hoses from Samco Sport to replace the factory lines and a slim fan from Infinite Auto.

Finally, anyone following along should note that the engine must be cold when attempting this operation. At temperature, the cooling system is under pressure, and on top of potentially getting scalded by hot coolant, the antifreeze is corrosive to both skin and paint.

After the engine has sufficiently...        read full caption After the engine has sufficiently cooled, Pro Street tech "Fat Kid" begins the job by disconnecting the battery's negative cable and raising the front of the Civic to empty the radiator. Pulling out the old stock unit involves emptying it of coolant (through a drain in the lower tank), detaching it from the compartment by disconnecting the fan motor and hoses, and ultimately removing the upper brackets and cushions that secure it to the radiator support. At that point, the exchanger is free enough to pull up and out. Those doing something similar should know that if the Civic has an auto transmission, cooler lines will also need to be disconnected. In addition, for accessibility, the coolant reservoir tank should be removed; it comes out by simply pulling it straight up.	Arpon lined up a radiator...        read full caption Arpon lined up a radiator from the cooling specialists at Koyo. Designed to fit like original equipment, each unit is built from aircraft-quality aluminum, comes Heli-arc welded, and features a core that's been NOCOLOK treated, a brazing method for resisting corrosion. Additionally, each radiator comes polished, and Koyo purports 20 to 30 percent more cooling than factory heat exchangers. Fat Kid also shows us the Infinite Auto fan and Samco hoses going in next.	Infinite's 10-inch slim fan...        read full caption Infinite's 10-inch slim fan is rated to move 1,500cfm and includes a universal mounting kit, adapting it perfectly to the Koyo EG radiator. There's also 12- and 14-inch versions available and all fans can be configured to either push or pull. Arpon has chosen to use his to push, whereas the stock fan and cowl are designed to pull.
Here's the primary reason...        read full caption Here's the primary reason Arpon is using a slim fan-clearance. You'll notice the considerable difference in thickness between the Koyo (right) and stock heat exchangers. Sure, we could probably use the OE fan and cowl, but imagine how deep the profile would be if the Koyo was set up that way.	Fat Kid hooks up the Samco...        read full caption Fat Kid hooks up the Samco Sport hoses to the radiator with OE clamps, and does the same for the reservoir hose. Samco says its radiator lines are engineered to withstand coolant temps in excess of 300 degrees Fahrenheit and come in seven different colors, each finished in a high gloss. They're available in standard blue, red, green, purple, yellow, orange, or black, which is what Arpon went with. With the hoses on, the exchanger can drop back onto its tabs in the engine compartment.	The other ends of the hoses...        read full caption The other ends of the hoses are reconnected to their respective fittings on the engine, and then Fat Kid re-secures the top bracket and cushion to the support. After that, the fan motor is plugged into its connector on the harness. The connector for the fan has been cut from the former radiator and spliced to the Infinite fan.
With the radiator strapped...        read full caption With the radiator strapped and plugged in, it's time to refill it with a mix of antifreeze and a proper wetting agent like Red Line Oil's Water Wetter. Wetting agents are said to both prevent corrosion and help reduce coolant temps by improving heat transfer in ethylene and propylene glycol antifreeze systems.	The Kid finishes off by sliding...        read full caption The Kid finishes off by sliding the reservoir tank back into position, capping off the radiator, and reconnecting the battery. Then the engine is run for a good half hour while Fat Kid and Arpon do a thorough leak check. Once everything checks out OK, Arpon can hit the road.