|
Researching engine sounds produced some more information.
Knocking on start up is a good indication of piston slap. The piston is too loose inside the cylinder and is slamming against the cylinder wall. As the aluminum piston heats up, it expands more than the iron block around it, and begins to fit in better.
A diagnostic test goes like this . .. . isolate the knocking cylinder, squirt in a table spoon of motor oil . . . if the sound does not occur or is greatly reduced . . . its piston slap.
You probably don't have enough reason to tear into the engine and fix it, or spend thousands on a (probably incompetent) rebuild at a local machine shop. Piston slap means your engine will fail long before an engine without piston slap. But it probably won't blow up tomorrow, or even next month.
|