Piston Slap: Duratec Oil Leak, Explained

Sajeev Mehta
by Sajeev Mehta
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.

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  • Terry Terry on Mar 02, 2011

    1st of all...,.I deal with this leak every single week on the job. The AJ V6( as used in the Mazda Tribute, 2000+ MPV, and Mazda6) originally came with the elastomer-imprinted aluminum spacer/gasket, and yes, with miles and age they did indeed seep oil. The solution is simple--replace the pan gasket, and be sure to use RTV at the junction of the front cover and block girdle. I recommend Permatex Ultra-Grey RTV Sealant. In cases where the oil drain plug is stripped, and a new pan is the recommended repair, the new pan will be of the grooved type, with a gasket inserted into the oil pan groove. As with the above gasket type, RTV needs to be applied to the pan/cover junction. The new pan will also have rubber seals in the oil pan bolt holes to seal the bolts as well. Other areas of leakage are the junctions of the block girdle to the front cover, and the head gasket junction of the front cover. Another common oil leak is the crankshaft front seal, and in a few cases, the rear main seal as well. Rarely do I see valve cover gaskets leak on these engines, but they do come in from time to time. A tip--when changing oil, before loosening the drain plug try torquing it to 19 ft-lb. If the bolt spins, the pan is stripped. There are kits to repair the threads. Time-Cert is the only one I recommend, but I prefer to replace the pan and start anew. Terry

  • Prowrench Prowrench on Feb 27, 2013

    I prefer to use motorcraft 7.3l diesel approved rtv on the t joints. this stuff is extremely tacky and thick, does very well with sealig problem leak areas.

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