Need Help With Knocking Noise
 

I have a knocking noise that is coming from what seems like the bottom of the motor. The noise starts about 2-3 minutes after I start the motor and continues untill I turn it off. I have had two mechanics look at it with two different opinions. The first guy told me it was probably the lifters and not to worry because it would go away. The other guy said it was probably the catalytic converter. However, I am a little concerned with two different ideas of what is wrong. Could it be something different? Thanks.

Try narrowing it down to the motor or cats, have you lost any performance? and have you checked the oil? i had the same problem (more of a ticking) in my cavalier when i got it, started using castrol and problem went away

I checked the oil in the motor and it was ok. I cannot tell that I have lost any performance from the truck. I am using a synthetic oil, but I cannot see where it would cause this to happen.

This might sound pretty stupid, but could it be a bad/broken motor mount?

Amount wouldn't cause a clicking sound .
If it was a bad engine mount , you would hear the cooling fan hit the radiator shroud whenever you started moving the truck forward or reverse (forgot which way the engine spins)

sounds to me like the engine gets sloppy when its warmed up and the oil thins out...try running a thicker oil but it could also be a rod knock which is very bad

I keep listening to it run and I seriously doubt it is the converter. I guess it could be the lifters? It sounds like it is coming from the oil pan.

thats even worse...if it sounds like its coming from the oil pan you got a rod bearing knock you need to start thinking about a replacement motor...maybe a 5.0?

I replaced the engine in mine and the other motor I got had a bad oil pump. A Horrid sound! You know the sound. Squealing. So I replaced the motor AGAIN! This time, runs as smooth as a 3.0 Vulcan should.

If that is the case I will upgrade to atleast a 4.0.

First trace the sound to the source and check the oil pump and see if it is good. If the sound is coming from the oil pan, that's where mine sounded bad and had to replace the engine.