Piston Slap: Duratec Oil Leak, Explained

TTAC’s resident gasket engineer, gimmeamanual, shares some thoughts on a previous Piston Slap. For starters, let’s go back to the original problem. In his own words:

In the last post, the OP says that they have tracked the leak to the interface between the block and the oil pan. He also mentions a “spacer” as well as RTV. The Duratec 3.0L (D30) engine variants have used two different gasket designs for the oil pan, but I can’t remember which for which years; one design uses metal-backed gasket referred to as an “edge-bonded” gasket (no groove on either the pan or girdle), and one design uses a “press-in-place” design (groove in the oil pan).

Fidgeting between multiple designs for something as “not customer facing” as an oil pan gasket isn’t a very smart move. Then again, perhaps one design is more cost effective, and not likely to draw attention to itself until well past the warranty period? Think about that, next time we talk Corporate beancounting. But wait, there’s more:

The D30 is a split-block design where the oil pan is attached to the girdle, which is in turn attached to the block; the oil pan also bolts into the bottom of the front cover. The block-girdle interface is indeed sealed with RTV, but the girdle-pan interface is sealed with a gasket. Sounds like the metal spacer he is referring to is the metal backbone of the edge-bonded design, but hard to tell without pictures. For the RTV, it’s unclear where this RTV is, but there is RTV at the block/girdle/pan-front cover interface at what is called a T-joint, so named because the vertical “seam” of the front cover-girdle/pan runs into the horizontal “seam” of the pan-girdle-front cover.

Clear as mud? Here’s the punchline:

The repair is fairly simple but has issues that must be paid attention to. The pan simply unbolts from the girdle and cover, but the gasket interfaces need to be cleaned and kept scratch-free. New RTV also must be put at the T-joint.

But wait, let’s get put on our tinfoil hats, just for funzies!

In doing some more digging, it looks like the Fusion never got the edge-bonded gasket, only the Jaguar AJ30, Lincoln LS, and early Mazda 6. But I can’t be 100% sure, because the two versions are made in the same plant, and there’s no way for me to know if an oil pan shortage resulted in the wrong engine pans being used on engines as long as everything else mates up correctly, which it may very well do. Stranger things have happened.

Moral of the story? Our trusty engineer lays it down cold:

The gaskets are not interchangeable!

Send your queries to mehta@ttac.com. Spare no details and ask for a speedy resolution if you’re in a hurry.