Charge air cooling system, function - GF09.41-P-3104M

ENGINE 275.953 in MODEL 216, 221 up to Model Year 8 

ENGINE 275.982 in MODEL 216, 221 up to Model Year 8 

Shown is model 240 

Fig 1: Identifying Charge Air Cooling System Function Diagram

Courtesy of MERCEDES-BENZ USA

The cooled air downstream of the charge air coolers has a higher density. This increases the cylinder charge and thus the engine output. In addition, the tendency to knock and NO X formation is reduced by the low exhaust gas temperatures

The maximum boost pressure becomes available only when the charge air temperature is lower than 70 °C. The charge air temperature sensor detects the temperature (B17/8) at the intake manifold.

A water/charge air cooler is built into each cylinder bank. Both water/charge air coolers are connected to the low temperature cooling circuit with low temperature cooler and electric circulation pump (M44). The circulation pump (M44) is actuated via the charge air cooler circulation pump relay by the engine control unit in the following manner:

• Switching on at a charge air temperature above approx. 47 °C
• Switching off at a charge air temperature below approx. 35 °C

The function of the charge air cooler is fully dependent on the air bubble free filling of the low temperature cooling circuit. A special tool (vacuum pump) is required for filling and the work instructions must be followed carefully.

Open the cap at the low temperature coolant circuit only when the charge air temperature is increased (power shortage) and the engine is cold. The coolant must reach up to the cap.