►Airtowater intercoolers have become much more prevalent in Mercedes and BMW vehicles in the last decade. Their efficiency makes them relatively small, making packaging in tight engine bays easier. With that said, they require a few more supporting parts to make the intercooler system function, and therein lies the problem.

Engines need cool air for combustion; otherwise, there could be preignition. An airtowater intercooler requires a constant coolant flow through the intercooler and heat exchanger to keep charge air temps in a healthy zone. Unfortunately, the water pumps that cycle the coolant through the cooler are electric and tend to fail without much warning. In many driving situations, the car may carry on with the reduced flow rate without an issue, that is, until you get on the throttle a little harder. No intercooler coolant flow means the charge air isn't being cooled, and the intake air temps are so high that the engine computer puts the car into limp mode. Unfortunately, the engine codes caused by this issue won't always directly point to it, and in our case, our X253 Mercedes GLC300 threw a power control unit code but not much else.

If this sounds like your issue, follow along with Gareth Foley, FCP Euro's BMW Expert, as he walks you through diagnosing a failing intercooler pump.



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