I just started getting a wierd noise from under the motor on my 4.7. It only happens when you start it up and it goes away after a minute or so of driving. It sounds almost like an exhaust leak but im not sure why an exhaust leak would not make noise after a few minutes. The sound gets louder the higher its revved. But then like I said itll go away after driving down the street for a minute. Anyone ever run into something like this?

 

yes but describe the sound more.. is it a hissing sound.........tapping , ticking, screaching... id maybe try to have someone start it while u have a listen under it. might be able to zero in with a piece of hose or pipe and move around till u hear where its comming from. sometimes works.

 

Is the sound kinda like across between a slap and a knock?

 

I have two issues making a similar noise on my 00 4.7 Durango (99,500 miles):
1. Lifters are a little noisy on start up. Last night I put in some "engine tune up" with am oil change. Start up this morning - no lifter noise.
2. The exhaust manifold studs are prone to breaking on these (at least on mine), causing an exhaust leak on start up. Once it warms up, the manifold expands, and the exhaust leak lessens.

Not sure if it helps you, but doesn't hurt to mention what I have seen.

 

If it sounds like a small exhaust leak, it might be just that. You might have a pinhole exhaust leak at the header, but when it heats up the header expands and seals up. It also might be that the oil drained out of the head when it was sitting and it takes several cycles for the oil pump to move oil back up into the head.

 

Yeah it just sounds like an exhaust leak really but it goes away after maybe a minute of driving. It doesn't really sound like anything internal in the engine. I just couldn't figure out why the sound would go away if its an exhuast leak but this makes sense now.