Mercedes-Benz W220 coolant loss: common leak points
W220 M112: why does the coolant go down and liquid mix into the oil?
The leak can be in the O-rings between the water pump and the oil wall or in the seal between the timing cover and the block. The coolant then flows inside the engine into the oil, so no puddle is left under the car.
W220 V8 diesel: where does the coolant disappear to?
One cause is a leaking EGR cooler (exhaust gas cooler), from which glycol flows into the intake manifold. The liquid is not visible under the car. The leak is located and the cooler is replaced, after which the coolant loss stops.
W220 V8 diesel: what does coolant in the intake manifold cause?
Glycol can clog the intake manifold and jam its flap shafts, and the vacuum actuator can break. This can show as an uneven idle. Replacing the cooler requires partly dismantling the intake manifold.
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