Strange inconsistent noises

[FreshBoxLive]

I bought my 2000 Tahoe Z71 Limited two months ago(240k miles), 5.7 4x4. Recently its been making a pinging noise on startup and idol, not always, but about 33% of the time. Sometimes it continues in gear for a few seconds, but always goes away eventually. Sometimes it goes days on end without making a sound. The sound i can best describe is a radiator fan chipping against a metal shroud. Doesn't effect performance at all. I had just enough time today to pop the hood while the noise was happening, seems the noise is coming from the bottom of the engine on the trans side. I crawled under where the noise was coming from and couldnt feel any vibration.

 

[east302]

Could be something in the exhaust. Hit it with a rubber mallet and see if you can spot something loose. Check the heat shields on the catalytic converters, sometimes their welds will break and rattle.




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