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RunCool Hood Louvers

Heat is the mortal enemy of the engine and everything in the engine compartment. Engines that run cooler also run faster, more efficiently, more reliably and last longer. However, running cooler is a real problem for law enforcement officers who have to sit beside the road with their engines idling for long periods of time, particularly in hot weather. This is especially a concern for K9 vehicles that simply must run all the time.

This problem is worse today than in the past due to the higher operating temperatures of engines required for emissions control. Before emissions controls, the standard engine operating temperature was 180 deg F. Today, it is 30 deg F higher (210 deg F) and, in some cases, higher than that.

Take a vehicle idling when the outside ambient temperature is 70 deg F. Now raise that temperature by 30 deg F to an outside ambient temperature of 100 deg F. Conditions that originally were not critical to overheating suddenly are.

So, how do you let the heat out of the engine compartment? Back in the Fabulous Fifties, hot rodders knew the secret, as did auto makers in the first third of the 20th century. They knew that hot air rises, and they let the heat out with hood louvers. In the 1950s, hot rodders would punch louvers in their hood, one louver at a time, which was both time consuming and expensive. That is not practical for police fleets today. Besides, that would also entail repainting the hood because the paint would crack and pop off when punching in the louvers.

Well, history is repeating itself. The answer for today is still hood louvers. RunCool® Hood Louvers, of Richmond, VA has introduced a line of patented hood louvers, designed with the help of a NASA aerospace engineer. These are effectively configured louvered and powder-coated panels of aluminum that are sturdily affixed to the hood with pop rivets.

The first group to start using the hood louvers was off-roaders who install big V-8 engines in Jeeps, and the hood louvers cooled down those overheating engines. In some of these conversions, the fuel rails in the fuel injection system were getting so hot, the fuel percolated in them. The hood louvers solved this and other problems. Recently, these hood louvers have also found homes on race boats, racecars, aircraft engines, giant quarry trucks, water pumping trucks in the desert that blast deep holes in search of oil and helicopter oil coolers.

Early on, hood louvers made their debut within the law enforcement community. Two years ago, Bruce Rucker, fleet manager for the U.S. Border Patrol in El Centro, CA, one of the hottest spots in the U.S., found out about these and started using them on some of his vehicles.

“[In this] kind of heat, our Border Patrol agents, and especially our K9 units, must have air-conditioning operating in the vehicles. That drives up the operating temperatures of engines beyond the point of what automakers envisioned for them. We found RunCool and purchased some of their louvers and installed them on some of our vehicles,” Rucker said.

Recognizing the high temperatures the Border Patrol members were facing, RunCool fabricated larger hood louvers for them. These new size large louvers were 11” x 17” per panel, versus the original size of 9” x 14”, which flowed more heat. In the summer of 2007, RunCool developed for the Border Patrol a Hi-Flow™ version of this larger panel with 19 louvered openings versus the previous 12 louvered openings, which flowed even more heat.

Work with the Border Patrol has continued. RunCool has now developed size Extra Large hood louvers ( 13” x 21” per panel ) in the Hi-Flow configuration (23 louvers per panel). “We are looking forward to trying out this new model, because when it comes to cooling an engine compartment, there is no substitute for getting the hot air out,” Rucker said.

Gabe Garcia of the Border Patrol in Casa Grande, AZ said, “Temperatures reach 120 deg F in the summer in the desert here. Many of the new trucks we are using have very tight engine compartments, with virtually no room for the air to circulate. We use the RunCool hood louvers to get that hot air out so cool air can come in. We plan to continue to add them to our vehicles.”

The hood louvers work because hot air rises and because the engine fan blows the heat up and out through the louvers. The engine compartment is like an oven. The hot air can’t go out of the top until hood louvers are installed. “Even on a warm day, if you hold your hand over those open louvers when the engine is at full operating temperature, you absolutely cannot leave it there for even a second or you’ll burn your hand; the heat is so great coming out of the engine compartment,” Rucker said.

Lower underhood temperatures also mean the A/C compressor and lines aren’t as hot, so the A/C is more efficient. Lower temperatures extend the life of everything under the hood, especially the battery.

“The installation was straight forward,” said Edgar Jaime, Border Patrol shop manager. “We followed the instructions, and after installing the first set, the technicians had no difficulties. The hood louvers are affixed with pop rivets, which are provided with the hood louvers. The riveted-in panels are quite secure.”

Other police departments are trying and using these now. Lieutenant J.B. Crawford of the Lexington, SC Sheriff’s Office tried a set on a Crown Victoria. “Our test was conducted on days with similar ambient air temp, barometric pressure, and with the identical engine-use time. In addition, the temp was taken with an infrared thermometer from the fire department,” Crawford said. These tests showed an underhood temperature drop of 31 deg F from the Standard Flow hood louvers. This is like dropping the outdoor temperature that much, say a 100 deg F day down to 69 deg F.

Chief Chris Garner of the Pelion, SC Police likes them and ordered RunCool Louvers for all his vehicles. Most recently, Garner tested the new Size Large Hi-Flow hood louvers on a 2004 Marauder. The test showed a 47-degree underhood drop in temperature. In the high heat and high humidity of South Carolina, they were experiencing battery life of only 18 months. Heat is worse than cold on battery life, so they are expecting battery life will also be increased.

Some departments like a low-key look, so the louvers can be powder coated by RunCool in colors to match the police vehicle, so they blend right in. Other departments, or certain departments on certain vehicles, like the tactical look, so they can choose the powder coated, semi-gloss black hood louvers. These give a purposeful look to a tactical vehicle, and on unmarked police cars, these hood louvers really give a non-stock look to further convince speeding motorists that “That couldn’t be a cop car!”

With engines operating at 30 deg F higher than two decades ago, hood louvers are both beneficial for vehicles in the South and in communities where summertime temperatures regularly get into the high-80s and beyond. For more information, visit the Web site or call RunCool at (804) 355-1758 for special police fleet pricing.

Robert A. Buerlein is founder of RunCool Hood Louvers in Richmond, VA. He can be reached at

Published in Police Fleet Manager, Sep/Oct 2008

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