Engine rattle

[rppoit]

Ok so a friend of mine owns a 04 envoy with the 4.2L I6. He bought it and right around 100K the engine blew. He replaced the engine, it drove fine for a while then right around 100k with the second engine he said the bottom of the engine started rattling like hell and its running on breakdown mode. He said it feels like its gonna gernade at any moment. hes taken it to two different shops and neither one could give him a reason why this was happening. I know the info is kinda vague but its all i have to go on at the moment. Kinda wanted to know which direction to start looking. Any ideas?

Forgot to add he made regular oil changes and monitored all his fluid levels. There is no water in oil and hes had no cooling issues

 

[The_Roadie]

Neither shop could tell him the main bearings are a huge suspect? Drain the oil and look for sparklies is the first thing I'd do. Metal in the oil - start shopping for another engine. Can't explain it.

 

[IllogicTC]

Sending a sample in to Blackstone Labs (it's like what, $25 for the tests?) will give all sorts of info. From the condition of the oil itself to the presence of what metals and in what quantity. There are certain levels which are considered completely normal, if I recall correctly they make sure to point out problems.