I understand that 'piston slap' is a much discussed topic, but I'm afraid I'm confused about it, still, and I hope someone is willing to help me out. I bought a 2003 Legacy with 72000 miles last Febuary - it is my first car. In August (with about 76000 miles at the time) a friend pointed out to me that the engine was making a tapping noise and suggested that I have it checked out. The noise is loudest when I start up and diminishes somewhat (so it seems to me) after the car runs for a time, but it never goes away completely. I drove from Michigan to New York with the noise, but with no other problem. The first mechanic I took it to listened for a minute or two and said the pistons are ruined and that I should replace the engine. He said that the car was probably poorly maintained by the first owner and that the engine could seize up at any time, which might destroy my transmission. So, I took it to a Subaru dealer for a second opinion. The mechanic there, too, recommended that I replace the short block (with a remanufactured one), but when I asked whether poor maintenance caused the problem and if, therefore, I should expect problems with other systems in the car, the mechanic told me that the problem was a defect in the piston design, that Subaru had a 'campaign' about the problem and would have replaced the pistons for free if my car had less mileage. When I asked what would happen if I didn't replace the pistons or the short block, he said the noise would get worse. When I asked if the problem was more serious and if the engine might seize, he began muttering about noise and problems and having to replace something, etc. I couldn't get more out of him, except that Subaru's are great cars and mine was worth repairing. His responses made me think the noise was a matter of piston slap.
The problem is, of course, the car isn't covered by any warranty and the expense of replacing the short block is all mine. Is there any way of determining whether or not the problem is 'piston slap' caused by the design of the pistons or if the problem is that the pistons are seriously damaged? (I've read some people report that they heard piston slap in their cars even after the car warmed up.) What is the consensus now, is piston slap something that could harm the engine, does it need to be fixed? Is it worth replacing the short block if the car is no longer under warranty?
Thanks for any advice you can offer.