Visual inspection of the system for leaks (Mercedes-Benz S-Class W126)

Check coolant hoses for porous areas by squeezing and bending, hardened hoses should be replaced.

The hoses must not sit too short on the connection nipples.

Check the tightness of the clamps on the hoses.

Check the radiator filler cap gasket for damage.

Warm up the engine and check for coolant leaks in the area of the coolant pump.

If the coolant leaks out of the pump hole on a hot engine, the pump shaft O-ring (oil seal) is usually defective. In this case, replace the coolant pump.

Sometimes it is difficult to locate the leak. In this case, a pressure test in a workshop is recommended (a special device is required). At the same time, you can also check the radiator cap overpressure valve.