I’m new here and I have some questions.

[Waterloo]

The CAC is the Charge Air Cooler. It sits on top of your radiator and feeds air to the turbo and intake side of the motor. Proper air volume is essential for these variable vein turbos to operate correctly, more so on the CM-871 and newer motors, but the same still applies to your CM-870. The CAC usually has a life expectancy of 800,000 miles with proper care, but can go longer. Eventually they just fail, as the years of dirt and dust pretty much choke them off, and or leaks or cracks develop.

On my truck, the CAC tested out fine, but I was still having issues with boost. I replaced the old unit with a new OEM, even though it past all of the tests, it was toast. That new CAC solved the issues I was having.