I have a 1999 Gmc s-15 sonoma with a mild engine knock on cyl #3 on 1999 GMC Sonoma

When the engine is fully warmed up the noise almost goes away! We have pulled the motor and dis-assembled, all wrist pins are a little loose but #3 isnt any worse than the other 3.Also all rod bearings look good, and the main bearings on each side of the #3 rod look ok. All pistons mic to be standard size. Are there any odd causes for this type of noise in this year model motor? Please HELP!!!

by in Hawkins, TX on July 17, 2012
2 answers 3 comments
ANSWER by on July 17, 2012
Interesting one...did you use oe parts for rebuild or aftermarket?
COMMENT by on July 17, 2012
Haven't rebuilt, just tore down to check valves,guides,pistons,rings,etc.
ANSWER by on July 17, 2012
Why do you say #3 is the problem? How did you test,pull Plug wire while running? Or something else. 1st answer ask about a rebuild,i missed that part.
COMMENT by on July 17, 2012
Pulled plug wire also stethoscope test its Def coming from 3 no rebuilde yet just diagnosis at this poi.
COMMENT by on July 17, 2012
This is a puzzle,i have been doing this a long time.Most noise gets worse in a warm engine. I know a machinest/motor builder, been doing this a long time too.I'll ask this wizzard and get back if can help.Something is expanding and then fits better.