Benefits
• Engine, oil and charge-air reach optimum operating temperature very quickly
• Prevention of white smoke by preheating the charge-air during idling and low-load operation
• Charge-air cooling during load-operation
Function
Illustrations apply similarly to other cylinder configurations.
Engine coolant circuit (high temperature HT)
After starting the engine, the engine coolant pump (6) pumps part of the coolant through the lube-oil heat
exchanger (3) into the cooling chambers of the crankcase (7). The other part of the coolant passes there
directly via a flow restrictor (5). The coolant flows around the cylinder liners and into the cylinder heads.
The coolant flows through the coolant chambers and bores of the cylinder heads. The coolant then flows to
the thermostat (4) via the coolant collecting lines (1) on the left and right.
The thermostat (4) diverts the engine coolant to the external engine coolant cooler when the engine is under
load (warm engine). Cooled engine coolant coming from the engine coolant cooler then returns to the engine
coolant pump (6).
The thermostat (4) leads the engine coolant directly to the engine coolant pump (6) when the engine is cold.
Bypassing the engine coolant cooler allows the engine, lube oil and engine coolant to reach operating tem-
perature quickly.
The engine coolant expansion tank is installed at the highest point of the cooling system. It compensates
engine coolant quantity and pressure and is connected to the circuit by an expansion and vent line (2, 8).
The engine is generally equipped with a preheating device.
Drain plugs are provided at the lowest points of the engine coolant circuit.
62 | Series 4000 Engines | MS15065/01E 2019-01
TIM-ID: 0000072882 - 001
