Chilly Reception

The radiator is the largest heat exchanger on a heavy truck, and in the good ol’ days was the only one besides the heater core. Nowadays, complex engine dynamics and cab-comfort requirements require at least two others: the charge-air cooler (sometimes better known as the air-to-air aftercooler) and the air conditioning condenser. High power and torque may also mean still another heat exchanger: the transmission cooler.

Often all of these are mounted at the front of the truck, adjacent to each other. This makes for a crowded collection of fins, tubes, hoses, pipes, and petcocks — a veritable Dagwood sandwich of parts stacked on end behind the grill. Bugs and debris smack into the leading surfaces of this sandwich as the truck moves down the road. Over time, the buildup impairs the heat-exchanging efficiency, and it needs to be removed.

How are you supposed to clean out these devices? Ah, that’s easy, you say: high-pressure water or air.

Not so fast, buddy. The various cores and adjacent parts may be made of aluminum, brass, steel, plastic, and rubber, and each reacts differently to outside forces. Blasting it all with 1,300-psi hot water may be an answer to the cleaning chore, but it’s not the answer.

The best general advice is to go easy on the pressure and scrub carefully. But somewhere on the property should be manuals and service bulletins describing what exactly is installed on the vehicle in front of you, and what you should and should not do to those devices. There’s a reason the various companies’ tech writers spent time on service bulletins. You can also go on-line to the truck-builder’s web page and see what you can find out about the radiator and everything else you have to deal with. You might also note the name of the component’s manufacturer, and go to its web page, too.

If you do want to use a blast of air to clear a blockage through the heat exchanger cores, blow in the opposite direction to the natural airflow, of course, but don’t use more than 70 psi. You can remove the intercooler for better access, but when you do this remember that dirt can get into the heat exchanger or the hoses and pipes to “dust” the engine when you fire it up.

High oil temperature, excessive fan cycling, and maybe only a little heat from the heater often signifies a cooling system problem that may require a full cleanout. To check the radiator for leaks, pressure-test the cooling system. With the engine cold — this is when the system leaks most — pressurize the system to 15 to 18 psi and verify that there are no leaks, either in the radiator core, header tank face, or in existing hose joints or in any replacements. Pressure-test the radiator cap. It should hold a minimum 5 psi, but check with the manual regarding correct system pressure.

Look in the top of the radiator. If the coolant is rusty and has a thick-looking consistency, or if there are deposits on the top tubes in the header, mechanics should follow the recommended procedure to remove rust, solder bloom, corrosion byproducts, and all the rest of the stuff that’s plugging the radiator tubes.

Check your spec, too. The first line of defense should be a bug screen either on the grille or behind the grille and ahead of the heat exchanger group. This stops the bugs with their corrosive body fluids from getting into the cores of the different heat exchangers.

The screen needs regular maintenance to keep it clear, as well, but keeping out bugs means there’s less for dirt to hang up on.Sooner or later, whether it’s here or someplace down south, you’ll fire up your AC and hope that the compressor and clutch are working well enough to blow cold air out the vents. There’s a tried-and-true way to take some of the guesswork out of air-conditioning system maintenance: APAds, made by Index Sensors, electronically monitors and lubricates the AC compressor and other parts of the system.

“Think of it as the fuse in your AC system,” says Gary Wilson, marketing and sales manager for Index Sensors. “When the system detects harmful conditions, such as high or low refrigerant pressure — or high or low voltage — it temporarily suspends compressor operation, preventing rapid cycling and premature wear and tear.”

Wilson says APAds also saves troubleshooting time and service costs because technicians can diagnose an AC problem by reading APAds’ simple LED blink codes.

APAds is available as a standard component on Volvos and is a factory option on other class-8 trucks. For more information: www.indexsensors.com, or call 1-800/726-1737.