2002 S600 (220.178) with M137.970; 51K miles.

* Engine oil cooler is leaking; renewal requires removal of both cylinder heads.

* Per WIS (AR01.30-P-5800L, Remove/install cylinder head), the "sealing surface of both the crankcase and cylinder heads are provided with an 0.8mm thick silicone layer during series production. Silicone sealant is applied in the gasket area when carrying out repairs only if shrink holes are present." The specified sealant is Loctite 5970 (003 989 98 20).

1) Could someone please clarify this procedure? Is M-B requesting sealant be spread over both sides of the new head gaskets or only in select areas of the gaskets?


2) With the cylinder heads removed... fragments of the old sealant are present on both the head and crankcase mating surfaces. The sealant fragments can easily be removed, with no damage to the surfaces. As such, do the cylinder heads need to be "dressed" with a light milling or can they be reinstalled as is, with only a manual surface cleaning?