Mystery Rattle that comes and goes

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Joined
Apr 11, 2024
Threads
9
Messages
22
Location
Tampa
Hey all, I’ve searched this forum and cant quite find what I’m looking for. I noticed a metallic rattle sound on start up today and high revs that eventually went away after about 2 minutes (lastest update: the noise goes away after about 1 minute) My first instinct was that it was a heat shield. But checked those and they appear fine. Sound seems to come from under the engine maybe passenger side. Also noticed there’s no oil leak but oil has caked around the oil pan. Owned the LC for about 3 weeks now. It’s a 2003 LC with the 4.7 V8 engine btw. New Update****Couldn’t hear the rattle this morning. I have no idea now lol

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Missing 10mm socket?
 
I’ve heard the same rattle under my ‘04. I assume(d) it’s the heat shields too, based on the 100 series FAQ thread. Mine is most noticeable when I pull away from the house under low RPM’s, or when I start it on colder mornings.

My current plan is to get the truck higher off the ground and double check around the shields and metal connections. As of now I can’t find the rattle and it’s not consistent with startup.
 
Oil leak might be rear main seal. That would be my best guess. I have the RMS leak and it still doesn’t leave a drop on the driveway so I’m letting it go for now. Eventually I’ll get it fixed but it’s not a huge priority for me right now.
 
I have a similar high pitched rattle on start up. I started touching stuff and when I touched the passenger side heat shield on the cat, it stopped. What can you do to fix that for good?
 
Rattle is gone this morning. Not sure what it was but I’ll be paying more attention to it for a while until I know it’s gone. One thing about these LC’s is that they seem to repair themselves sometimes lol.
 
I have a few hose clamps on my heatshields to silent rattles. The other day during a full day trip I heard a rattle (this is after like a year+ of no rattle). I got under there and gave one of them a tighten and it went away.
 
Valve cover, headers or something loose and they tighten up when they get warm they expand and sit tight?
 
My aftermarket catalytic converters rattle when chilly, but I see you have OEMs.. keep an eye on them, they'll be gone if you don't, and aftermarket cats suck!
 

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