Volvo D11F Operator's Manual And Maintenance Instructions page 73

Maintenance and Service 69
When using a pressure washer to clean the vehicle, do not direct the spray at
electrical components in the engine compartment such as the alternator,
starter and compressors. Water spray from pressure washers can damage
electrical components.
The simplest method to clean the package is to use air pressure or a water
stream. This should be done from the back of the core. Air pressure should not
exceed 200 kPa (30 psi) for radiator and charge air cooler cores. The use of a
fin comb is also a good tool to loosen bugs and dirt from the fins. If dirt cannot
be cleaned off with this procedure, consult your Volvo Truck dealer.
Cleaning Charge Air Cooler and Radiator (typical radiator shown)
Inspect the charge air cooler for cracks at every inspection. DO NOT operate
the vehicle with a damaged or broken charge air cooler. To do so would void
the warranty and the engine will not meet emission regulation requirements.