Function of the coolant circuit, with diagram - ra83001400402x(0402)

WARNING: This page does not describe the selected car, but rather 42 other vehicles, including the 1999 Mercedes-Benz S600, 1999 Mercedes-Benz S500, 1999 Mercedes-Benz S420, 1999 Mercedes-Benz S320, and 1999 Mercedes-Benz CL600. However, it is still accessible from the selected car via links, so may be relevant.

Model 140 with auxiliary heating

Coolant circuit up to approx. 55°C

The circulating pump (A31m1) of the vehicle heating systems delivery unit (A31) delivers the coolant to the heating unit (A6) via the thermostat (1).

In the heating unit (A6), the coolant is heated, passed through the switch-over valve (5) and then distributed among three coolant delivery circuits.

NOTE: The engine is not heated if the coolant temperature is less than approx. 55°C.

Delivery circuit 1:

The coolant is delivered to the heat exchanger (2), divided in the heat exchanger (2) and pumped back to the circulating pump (A31m1) via the left duo valve (A31y1) and the right duo valve (A31y2).

Delivery circuit 2:

If the windshield washer fluid temperature is ≤ 30°C the coolant is pumped back to the circulating pump (A31m1) via the windshield washer fluid heater (4) and the thermovalve (6) for the windshield washer fluid heater.

Delivery circuit 3:

If the outside temperature is ≤ 10°C, the coolant is pumped back to the circulating pump (A31m1) via the window heater (3) and the thermovalve (7) for the window heater.

Fig 1: Coolant Flow Diagram (Coolant Circuit Up To Approx. 55°C)

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Coolant circuit up to approx. 55°C, thermovalves for windshield washer fluid heater and window heater open.

Coolant circuit above approx. 55°C

At coolant temperatures above approx. 55°C, the thermostat (1) starts to open and allows a certain volume of cold coolant to flow from the engine to the heating unit (A6) of the auxiliary heater.

In the heating unit (A6), the coolant is heated, passed through the switch-over valve (5) and then distributed among three coolant delivery circuits.

Delivery circuit 1:

The coolant is delivered to the heat exchanger (2), divided in the heat exchanger (2) and pumped back to the circulating pump (A31m1) via the left duo valve (A31y1) and the right duo valve (A31y2).

Delivery circuit 2:

Delivery circuit 3:

If the outside temperature is ≤ 10°C, the coolant is pumped back to the circulating pump (A31m1) via the window heater (3) and the thermovalve (7) for the window heater.

Fig 2: Coolant Flow Diagram (Coolant Circuit Above Approx. 55°C)

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Coolant circuit above approx. 55°C, thermovalves for windshield washer fluid heater and window heater open.

Coolant circuit above approx. 65°C after set in-car temperature is reached

Once the set in-car temperature is reached and the coolant has reached a temperature of above approx. 65°C, the coolant flows through the engine and the fully opened thermostat (1), and through the heating unit (A6) and switch-over valve (5).

Delivery circuit 1:

The coolant is pumped through the bypass line to the left duo valve (A31y1) and right duo valve (A31y2).

From there, the coolant travels back to the circulating pump (A31m1).

Delivery circuit 2:

If the temperature in the windshield washer fluid tank is > 30°C, the thermovalve (6) for the windshield washer fluid heater blocks the flow of heated coolant through the windshield washer fluid heater (4).

Delivery circuit 3:

If the outside temperature (air) is > 10°C, the thermovalve (7) for the window heater blocks the flow of heated coolant through the window heater (3).

Fig 3: Coolant Flow Diagram (Coolant Circuit Above Approx. 65°C After Set In-Car Temperature)

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Coolant circuit above approx. 65°C after set in-car temperature is reached, thermovalves for windshield washer fluid heater and window heater closed.