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The noise the engine makes kind of sound like (past times in my life with different cars) a low oil engine noise in its frequency - how often it ticks. It stays with RPMs, so it's fast.

But I didn't want to say it sounded like "tapping" because all the tapping I've ever hear had a high pitch to it. Mine has a lower tone than that - almost like if you hit a small metal bucket.

I hope that helps a little?
Is the noise consistent in tone and speed, or erratic? Is it worse/better if you let off the gas? (Additional oil seeming to help aside) it might be spark knock, which sounds like shaking small rocks in a metal bucket. Knock would be worse in high load situations when you are in the gas and would stop when you let off.
 

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Discussion Starter #22
Thanks for the note Kelly. The noise is consistent with tone, and the speed increases as as RPM's and load do. But it's silent when not going up a steep hill or accelerating, there must be a strong load on the engine to hear it. So it does not get worse when you let off the gas, it goes away.

I have an appointment tomorrow at the dealership to diagnose it. Unfortunately, with 180,000 miles on it, I'm afraid they'll find many things wrong that doesn't contribute to making the noise, but want me to pay for several sub-par performance issues other than that new noise.

Oh, and after it being quiet after chaing the oil just a few days ago, the noise is back at the normal oil level (with the new oil).
 

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Discussion Starter #23
After paying the dealership to diagnose, they said I have 3 exhaust manifold bolts missing and the two motor mounts need replaced.

I find it hard to believe motor mounts would cause the noise but not a vibration; the tech said it could be hitiing the firewall; does that sound reasonable to you guys? They wanted $1700 for just one of the motor mounts! It's listed at 12 labor hours to replace the driver's side.

Also, they recommended putting the exhaust manifold clamps on both front and one rear (where each bolt is missing). I looked carefully at all 3 missing bolts and I don't see any space between the surface, gasket, or manifold. So does it create space when under load? It's hard to believe rushing air would bend the heavy metal, but I do know little about these things ...which is why I'm here asking for your generous help.

So I will install the manifold clamps, since they are about $100 for all 3 and doesn't look too hard. Then if the noise is still there, I'll look into the mounts, which I may not be able to do since one of them is listed as a 12 hour job. The passenger side is listed at 2 hours.

This awesome 5.3 short body Rainier has been AWESOME but it's probably only worth $1500 at this point with 180,000 miles on it. It's a shame because I just replace every single suspension component on the front (including inner + outer Tie rods) and the truck feels super tight right now ...like a new car.
 

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If (BIG IF) - the stealership is right, Neither of those issues are cause to retire it or stop driving it.

I say drive it like it is. My two cents
 

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Discussion Starter #25
OK, I installed the three manifold clamps on 3 corners missing bolts and the noise is STILL there.

Replacing the motor mounts is a 13+ hour job, so I don't know if we'll ever do that. If you think I should, let me know!

I just realized, I have some water dripping out of the exhaust when first starting the engine, so I'll put some JB Weld there and see if that could be it.

I got a recording of the noise and will post it here as soon as I figure out a way ...maybe someone could identify it?

While in the driver's seat, it sounds like it's coming from the passenger side and when I'm in the passenger's side, it sounds like it's coming from the middle to passenger's side.

I may overfill the oil by 3/4 of a quart just to see if it goes away again. I'l report back when something changes or when I've tried these things. Any comments are welcome ...thank you.!
 

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Why not just put manifold bolts in if they are missing? Are they broken off in the heads?

Clamps sound like a cheap band aid that still leaves alot of questions unanswered and a waste of time / $. Again my $.02

Water dripping from the exhaust is normal and no reason for concern unless it does it after the motor / catalytic converters are warmed up and there is an excessive amount.
 

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Discussion Starter #27
Yes, they're broken off and would not pass our PA state inspection, so I had to do it anyway. I checked reviews on the clamps and the reviews have very good results. The manifold didn't look like it had the tiniest space between the head and manifold gasket. So I pretty much figured I'm not hearing an exhaust leak; I mainly did it to pass inspection.
 

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Gotcha. So PA inspection looks at your exhaust manifold bolts?

WOW! And I thought NC inspection was peculiar!
 
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