The chassis-mounted charge air cooler, originated by Volvo and Mack, was a breakthrough in engine power and efficiency, paving the way for the diesel engine’s ability to meet extremely tight particulate and NOx emissions regulations. By increasing the density of the air entering the engine, the device increases power. Allowing the engine to ingest the maximum amount of air at the lowest possible temperature reduces compression temperature and engine heat stress and helps combustion efficiency.

For these reasons, an efficient charge air cooler helps guarantee optimum fuel economy and the lowest possible engine-out particulate and NOx emissions. It also minimizes cooling system stress, since heat not removed in the charge air cooler must be taken away by the radiator.

Michael Donnelly, service manager at NHC Kenworth in Little Rock, Ark., says the most obvious symptom of charge air cooler problems to the driver is reduced power, while for the fleet operator, the obvious symptom is increased fuel consumption. The driver also may notice higher engine operating temperatures and even whistling noises, says James Nichol, an instructor at the Universal Technical Institute’s campus in Avondale, Ariz.

The driver also may hear a “pop” sound right before power drops off, which can indicate the failure of a hose or hose clamp, says Mike Arzamendi, Peterbilt dealer training director. The cooler should be serviced as soon as it’s clear that its performance is borderline. A bad charge air cooler also can put extra stress on the turbo and exhaust manifold, according to Cummins.

Inspect routinely

Routine inspection — at least at every oil change — is critical to maintaining performance. Reduced airflow through the outside of the cooler and dirty surfaces can affect performance just as much as leakage from the pressurized side.

The number one issue is dirt, mostly in the form of bugs. Experts suggest regular inspection of the area behind the cooler and the unit itself for clogging. Donnelly suggests flushing the unit out from the rear with a pressure washer designed to treat truck finishes gently, while Nichol suggests a stiff nylon brush. And when bugs form the worst kind of goo, it’s best to remove the device to flush it out from the rear, says Ed Saxman of Volvo Powertrain.

A careful inspection around the unit, with the hood closed, will reveal any wayward air seals or flaps blocking airflow, or any hood or other body parts that may have settled or shifted sideways so as to cause rubbing. This problem often can be fixed before the cooler perforates and leaks.