DuaneC63

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 cylinder(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

biker349

what years does this effect? i have a 2004 cl600.

DuaneC63

It only effects the M156 6.3 motor with the engine Id# per the bulletin. I think you should be OK as the M156 engine did not start production until MY 08.