Need some help diagnosing warm engine only, rpm dependent engine rattle 96' FZJ80 (1 Viewer)

[M0untaineer]

Ok...so did some more looking/listening around...to me it definitely sounds like it's coming from the passenger's side exhaust manifold area...In searching the interwebs, seems that exhaust leaks under load produce a very similar noise to what I seem to be hearing...I don't see/smell any obvious exhaust in the engine compartment...but the sound and symptoms seem like this is a match...I listened to the engine through the valve cover and didn't hear anything- the sound seemed to be exterior to the engine...any prime suspect sites that I need to focus on first, or any tricks to locate the leak if that's it?...since the car will only produce the sound under load at certain rpm ranges and only at normal engine operating temp, coupled that there's nothing moving when I put the truck in gear and sit on the brakes and rev to 1265 rpm and the sound is still produced, but not when I rev the engine in park/neutral...

 

[fjfodee]

Good to hear you narrowed it down and it's nothing major.

 

[LFD2037]

@M0untaineer

Ok...so did some more looking/listening around...to me it definitely sounds like it's coming from the passenger's side exhaust manifold area...In searching the interwebs, seems that exhaust leaks under load produce a very similar noise to what I seem to be hearing...I don't see/smell any obvious exhaust in the engine compartment...but the sound and symptoms seem like this is a match...I listened to the engine through the valve cover and didn't hear anything- the sound seemed to be exterior to the engine...any prime suspect sites that I need to focus on first, or any tricks to locate the leak if that's it?...since the car will only produce the sound under load at certain rpm ranges and only at normal engine operating temp, coupled that there's nothing moving when I put the truck in gear and sit on the brakes and rev to 1265 rpm and the sound is still produced, but not when I rev the engine in park/neutral...

Mine makes the exact same sound under the exact same conditions. Have you found the problem?

 

[CruiserCoLittleRock]

bring it by the shop...i have a really cool thermal camera, if you have an exhaust leak it will show up. and we will be able to see if the components are heating evenly.

 

[LFD2037]

bring it by the shop...i have a really cool thermal camera, if you have an exhaust leak it will show up. and we will be able to see if the components are heating evenly.

Interesting idea. I have thermal cameras at work. How do you go about doing this? Check temps when engine is cold or hot? I'd assume the hotter spots indicate exhaust is leaking at that point?

 

[CruiserCoLittleRock]

you would use it on a cold engine at start up and watch for exhaust gas hot plumes escaping from any mating surfaces. It would show up as better contrast when the engine is cold. I would let the motor cool and repeat for a new area you might be concerned with, you will only have about 30 secs to have the best contrast at lower temps.

once the engine heats up you could compare heat along the entire exhaust bank and you would immediately know if a cylinder was not running correctly, since you have two manifolds on that side it should be easy to see a difference in effeciency.

if all else proves to be a false positive..ie dieseling, exhaust leak, etc.

I would stethoscope the exhaust valve body ( where the two egr pipes run to) on the egr circuit since you indicated the noise was coming fromt that side of the motor. I know the toyota v8's have real problems with those sticking and knowing toyota they probably used similar tech in previous versions found on the s6