I don't know if any one here is following the issue with defective head bolts on the M156 engine. However I am cross posting this from the C63 board. All M156 up to a certain engine number are subject to this failure. MBZ-USA will not retro fit with the new head bolts until they fail (snap off) causing the head gasket to fail. Rapid loss of coolant into the cylinders(s) is the first indication of the problem. Failures usually occur between 40K and 50K miles. The cost to repair is very expensive if you are out of warranty. MBZ-USA has a service bulletin out on this but will not provide a copy to customers. If any of you have had this problem please send me a PM. I am pursing this further. I would suggest a letter writing campaign to:
Mr. Ralph Fisher
Mercedes-Benz USA LLC
Customer Assistance Center
Three Mercedes Drive
Montvale, NJ 07645-0350

 

Hello I believe I just had a head bolt failure on my 09 ml 63 with approx 48k mileage . Started out with low coolant and cylinder 6 misfire check engine light . Rough idle when we added coolant and a good amount white smoke from exhaust . Looking for answers / cost for repair out of warranty and seeing posts on repair work at 40k ! Hoping MB will assist since this is a defect on their part