Hello all, I've noticed a weird pinging noise every time I shut my truck off. Was just wondering if I should be concerned? The iPhone seems to exaggerate the sounds as they are much quieter in person (Skip to 10 seconds). 1985 351w 4B HO engine, new plugs & wires, oil and filter has been changed, coolant has been changed, new thermostat & water pump.

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On a vehicle, noises like that are usually on things that are hot while running, then shut off and typically cool very rapidly.

I'm betting it's either your catalytic converter (probably not, that doesn't sound too much like a tin can) or it's your exhaust manifolds.

I'd bet if you loosened up all your manifold bolts on each side, then just snugged them up it wouldn't make a noise. It's free to try, and it's not like you're changing the manifold gasket, so give it a shot.

It could be someone has overtightened the manifolds then they expand when they're hot. Once they start cooling, it could produce a noise like that.

Might even be the bolts that hold your down pipe to the manifold.

 

Thanks for the response, did a bit more research yesterday and it most definitely sounds like the metal expanding and contracting. I've found the sound is coming from the exhaust manifolds. Probably doesn't help I didn't have the truck on long enough to fully warm up either. meh better safe then sorry.

 

Alright was working around the exhaust manifolds earlier and found something very odd. Found this random part just sitting beneath the passenger manifold it wasn't even bolted in or anything. Can anyone help identify what this is? Its extremely light and feels pretty flimsy perhaps a heat guard of some sort? I had no time to test for pinging after I removed it will get back to it later. (nothing like it on the driver side)

 

Looks like the hot air stove for the stock air cleaner. That part goes over the exhaust manifold and a flexible pipe connects to the bottom of the air horn on the air cleaner. There's a valve in there that's open when cold and the engine draws air from around the exhaust to help it warm up.