I know it;s hard to tell without hearing, But here goes bought a 93 dakota 120000 miles holds good oil-presure hot or cold, 3.9 v6 When first cranked it makes no noiese but after about 15 mins. of running or driving starts a bump like noise. Been around cars alot sounds like a mainbearing, but before i pull it any idea's,I thought a main or rod would knock all the time ? Checked the torqeconverter bolts, Can't pinpoint it listening with a hose can hear it anywhere ?

 

i would change the oil and add a bottle of Lucas......if helps then you know is mains or rods, something in the oil train.

 

Yea i changed th oil last week, 3 qt.s of 20-50 royal purple and a qt.of lucas, no change, I just don't understand why it don't do it the first start, If the oil pressure droped then yea but the oil pressure stays good, It don't tick none, sure sounds like mainbearing thump to me, I just don't to admit it,

 

Man do i feel better thought i'd take the belt off just to see, no knock the only thing loose is the fan clutch, Bout a inch of play, so i'm starting there

 

thats probably it, while you have it off why dont you change over to E-fans, they will free up horsepower and your fuel economy will go up

 

Put anew clutch on it all's quiet now,

 

She's knocking again, took belt off all quiet.? Driving me crazy made me a belt useing a pair of panty-hose,{he,he] running it without the alt still knocked then without powersteering no-knock, Could it be the pump ? I hate to keep spending i thought it was the fan clutch to I got a stethoscope can't pinpoint the noise echo's threw everything, But take the belt off you can't hear it, If it was the timingchain it would do it with or without belt right ?