Posted by Alan Bowes on June 09, 1999 at 09:06:54:
In Reply to: Engine knock - Please Help! posted by David on June 06, 1999 at 12:21:31:
Good advice so far.
- In general, a rod knock tends to be more pronounced as you speed up the engine under a light load (or no load). It also tends to be a little higher pitched than a main bearing knock.
- In general, a main bearing knock tends to be more pronounced as you accelerate under a heavy load or lug the engine.
- I've heard some similar sounds related to wrist pin or piston wear/damage as well.
I believe someone had mentioned removing the spark plug cables one at a time to try to isolate the problem. This is always worth a try.
Whatever it is, the longer you drive it, the better the chance of serious damage to the crankshaft or other engine components.
I'd suggest pulling the oil pan and having a look. If it's a worn rod bearing that knocks that badly at idle, you should be able to locate it without even removing the bearing caps. Just twist each rod back and forth (I don't mean sliding them side-to-side) and look for the one(s) with the most play.
Check the journal for scoring and out-of-roundness with a micrometer, being careful not to scratch the bearing surface. If the problem is a worn rod bearing, there is a chance that you might be able to get away with replacing a rod bearing with the correct size insert and buttoning things up, although I must say that the chances are that the scoring or other journal damage may have gone beyond that point.
Alan