We are concerned with the three components which are connected with with the exit (always at the top) from the cooler (low-temperature), ie., the two turbo-chargers and the recirculated exhaust gas in the second part of the exhaust gas cooler. The result is, three return lines, which, brought together, end at a valve near the coolant pump.

From this point the coolant is either pumped from below, through the cooling jacket of the engine or directly back to the entrance of the low-temperature cooler. This can be decided by a control valve found below on the right next to the pump. In any event, the coolant assigned to the engine then flows through the exhaust gas cooler, before, depending on the position of the valve, it goes up to the high-temperature cooler or e.g., in the cold-running phase, flows directly to the pump.

It is also noteworthy, that in this case, the hotter coolant flows through the entire exhaust gas cooler in the same direction as the exhaust gas itself does, while the less hot coolant only flows through half the exhaust gas cooler but in the opposite direction. In any event, the recirculated exhaust gas is brought down to a lower temperature in two stages, before it is, once again, mixed in with the intake air. Thus, particularly in the Diesel engine, the temperature in the combustion chamber and in addition, the emission of nitrogen oxide is reduced.