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Importance of Charge Air Cooler (CAC) Testing for Diesel Engines

Leaking charge air coolers are one of the most common causes of reduced diesel truck performance. The problem is that the signs of a leaking CAC are not obvious to the operator or even the maintenance technician, until it is so bad that greatly increased fuel consumption is noticed. In a CAC air cools air, so there will be no obvious evidence of a leak, unlike a leaking radiator that leaves a puddle of coolant under your engine.

Our data shows that almost half of the charge air coolers over two years old have leakage in excess of the recommended specification. The result is a lot of excessive fuel being consumed, loss of power and other engine issues being created, reducing the profitability of your business. For a fleet of 15 trucks, leaking CACs can easily cost you over $100K in extra fuel bills. The cost of the CAC tester and the 20-minute test is quickly earned back in improved engine performance and the knowledge that you accurately know the operating condition of your important air intake system CAC.

You might ask “how do I know when a Charge Air Cooler is leaking then?” The answer is that it requires a pressure drop test. That can seem daunting at first, but Dura-Lite offers a CAC test kit that is easy to use and can test virtually any CAC even when it’s installed in the vehicle. With Dura-Lite’s Tester-Kit™, one side of the CAC is plugged and the other has a simple pressure gauge and plug installed. The CAC is typically pressurized to 30 psig (or the manufacturer’s recommendation) and then isolated to test for leakage as measured by the pressure gauge. Dropping more than 5 psig in 15 seconds generally means your CAC is leaking excessively. All this can be done in 20 minutes or less.

Check out our video for more detail on using Dura-Lite’s CAC Tester-Kit

Find out how much money a leaking charge air cooler could be costing you with our leaking CAC calculator.

Here’s a quick look at some of the risks you take when regular CAC testing is neglected:

Reduced Engine Power

Efficient fuel combustion in a diesel engine relies on a full supply of cool, dense air. This air has been compressed by the turbocharger and then cooled by the charge air cooler. Any leakage of intake air from the CAC steals power from the engine.

Reduced Fuel Economy

If the engine’s power is reduced at a given RPM, then the engine is working harder and burning more fuel. Reduced fuel economy is one of the best indicators of a leaking CAC if it’s measured carefully and trends plotted. Of course, there are many factors that affect fuel economy, so the data must be compared for similar trips or periods.

Engine Overheating

In the worst case, as the CAC really starts leaking excessively, the cooling system can have trouble removing all the excess heat from the engine. An overheating engine can cause significant damage in a short period of time, such as premature piston, ring, and valve failure.

Soot in Engine Oil

Soot occurs naturally in every diesel engine; it’s why your oil turns black so quickly. In a normally operating engine, the small amount of soot that accumulates in the oil won’t change the viscosity of the oil or affects its lubricating capabilities. However, in cases like a leaking CAC, soot can become excessive, thicken the oil, and leave deposits in the engine. Left untreated, it can clog your oil filter or in the very worst case, clog up an oil passage and cause permanent damage. Soot sticks to components in your engine and is abrasive, accelerating wear. Soot can be measured in an oil sample if it accumulates fast enough.

Using a CAC test kit to check for leakage and doing routine oil samples is the best practice and such a simple procedure to insure long engine life.

You should test your charge air cooler every time you change the oil or perform preventive maintenance on your truck. That way, you know your truck and its systems are always ready to handle whatever jobs are thrown their way.

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