My 87 300D with new (4 years-less than 30Km) factory crate engine with a #20 head suffered either a failed head gasket or a cracked head. Pressure testing the cooling system resulted in a hydrolock. It is at the dealer being repaired under the warranty that came with the engine. The reason I went with the factory engine was the long 4year 50Km warranty that came with it-at a price. This engine has never overheated but from the time that it was installed I noticed a wisp of greyish-white smoke. Interestingly, even the dealer sends the heads out to be pressure tested and milled.

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87 300D 265Kmi
Factory rebuilt crate 603.96x engine at 200K