Testing cooling system for leaks - RA20001190170X(20-0170)

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.

Operation no. of operation texts and work units or standard texts and flat rates

20-1010

Special tools

Fig 1: Identifying Test Cap (124 589 00 91 00)

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Fig 2: Identifying Special Tool (210 589 00 91 00)

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Fig 3: Identifying Tester (124 589 24 21 00)

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

COMMERCIALLY AVAILABLE TOOLS AND TESTERS

Designation	e.g.	Make, order No.
7 mm socket wrench hexagon on a flexible shaft for hose clips with worm drive		Hazet, 42853 Remscheid Order no. 426-7

A newly installed cylinder head gasket is not watertight until the engine has reached its normal operating temperature, in other words until swelling has occurred. For this reason, do not pressure-test the cooling system when performing repairs until after the engine has reached its operating temperature.

Checking for leaks

The cap of the cooling system must not be opened unless the coolant temperature is below 90 °C.

A 2-stage cap is fitted to model 210; see note.

Turn cap (detent lock) to the 1st detent to release the pressure, then turn on to the 2nd detent.
Open 2-stage cap (screw lock) half a turn to release pressure, then unscrew.
Take off system cap.
Check coolant level and adjust to correct level if necessary.
NOTE: Model 124: pour in coolant up to the marking on the expansion reservoir.

Models 129, 140: pour in coolant up to the separation line between top part of expansion reservoir (black) and bottom part of reservoir (transparent).

Model 210: pour in coolant up to the marking (cast lug) on the bottom of the expansion reservoir.
Use the test cap and the tester to pressurize cooling system to about 1.4 bar.
Inspect all the cooling and heating water hoses and the connection points for loss of coolant.
Inspect the condition of the coolant hoses and hose clips; replace or re-tighten if necessary.

Fig 4: Checking Condition Of Coolant Hoses And Hose Clips
Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

NOTE: A 2-stage cap is fitted to the expansion reservoir of model 210.

The 2-stage cap eliminates the need for the overflow reservoir.

During the engine off heating phase, the pressure in the cooling system may rise.

The first stage in the coolant cap opens at 1.4 bar, the cooling system itself remains closed.

Only once the 2nd stage in the coolant cap opens (at 2 bar) does coolant flow through several vent drillings (a), the annular gallery (b) into the outlet connection (c) through a hose extension to atmosphere.

Fig 5: Identifying Vent Drillings, Ring Duct And Outlet Connection
Courtesy of MERCEDES-BENZ OF NORTH AMERICA.