I bought a 97 outback with a fried engine. Bought a used 2.5 engine with 70,000 miles on it. Replaced the engine, buttoned up everything and fired it up, heard a noise that to me was a slapping piston or something that went away within a few minutes of warm up. Sound is on both sides of the engine.
I've never owned a 2.5 engine, just my current 2.2 so I went searching. Apparently there is an issue with piston slap until it warms up.
<li type="disc">Diagnosis: The pistons are engineered for operation at temperature. In an effort to save weight in the engine, the piston skirts were shaved down. When the pistons are cool, however, they do not have sufficient contact with the cylinder to keep from 'slapping' or rattling against the cylinder sides. At temperature, due to thermal expansion, the pistons match up properly with the cylinder and do not rattle. <li type="disc">Reported solutions: In some cases, SOA has rebuilt the engine short block, while in others SOA prescribed "countermeasure pistons" with longer skirts that do not slap. Most dealers will initially state the sound is "normal." <li type="disc">Detrimental effects: SOA has said that the noise causes no engine problems or abnormal engine wear; Subaru engine expert CCR Engines of Colorado has said that the engine may experience a 10% reduction in life."
So I am thinking I am good to go with this engine transplant but I thought I would run it by the forum. Engine runs well on the road.