I've had a ML270CDI for two and half years with no problems. Recently the coolant warning indicator has started to come on regularily and the coolant needs replacing every 30-40 miles. It started on high speed short runs but over a few weeks comes on constantly.

Its been in the garage twice and had a pressure test. Both times diagnostics say its fine. The problem started to get worse so it went in a third time for two weeks. They removed thermostat housing and replaced the coolant pipe, then pressure tested. They said it was fine but as soon as the car was out of the garage the problem occured with greater frequency.

They have since replaced an auxillary pump under advice from Mercedes technical with no result. I have been informed technical now say to check the cylinder head for cracks.

Even with the problem the car has no loss of power or performance and its emissions are fine. Its just out of warranty so I'm concerned at the bill I'm running up.

Has anyone had a similar problem or any ideas?

 

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I've just heard the cylinder head has come back from testing and they have found it to be pourous.</P>


How does a cylinder head become pourous?</P>


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fancy word for it either being cracked or a flaw in the casting where the fluid was allowed to enter into the combustion chamber.