Rattling metal sound on cold start - Manifold or something else?

[digitalmarker]

Hey guys, my 1999 recently developed an annoying clicking noise while the truck is warming up. The noise gets quieter as the truck gets warmer, and usually goes away after driven for 5-10 minutes. Everything I have read up on it suggests this is a cracked exhaust manifold. I posted this on Facebook and got conflicting responses ranging from flex plate to stuck starter hitting the flex plate, etc.

Probably important to note the noise got a LOT more noticeable/audible right after I installed a new cat converter on the driver side, which is where it sounds like the noise is coming from.

I know there have been a few threads on this here, but wanted to confirm this is what a cracked manifold sounds like before I order the parts and attempt the repair. Thanks in advance.

 

[2001LC]

Make sure H - L shiftier full engaged. Then open hood and look around, pay special attention to fan and fan bracket.

Exhaust leak is possible, but sound is off. It may be your recording/sound that is off to me, IDK.

Did you replace the gaskets on O2's?
Did you replace exhaust gaskets at both ends of cat.

 

[digitalmarker]

Make sure H - L shiftier full engaged. Then open hood and look around, pay special attention to fan and fan bracket.

Exhaust leak is possible, but sound is off. It may be your recording/sound that is off to me, IDK.

Did you replace the gaskets on O2's?
Did you replace exhaust gaskets at both ends of cat.

I haven't moved the H-L Shifter but will check.

Nothing is loose under the hood, at least not obviously.

All gaskets, donuts and O2s, were replaced with the cat with brand new OEM units.

The thing is that the sound alway goes away after the truck warms up in place, or being driven for a bit. So whatever is causing this is affected by temperature of the engine.

 

[2001LC]

Exhaust leaks sound different, perhaps it's just the recording make sound different than I'd expect. As they do often go away at operating temp.

 

[archerwolf]

Check the corners of the heatshields around the cats especially near where the heat shield mounting bolts are. They tend to crack and vibrate with the exhaust. Installing the new cat might have made the crack worse.

 

[digitalmarker]

I posted this on Facebook and some folks suggested this could be a loose starter getting stuck? I have been having issues with my starter for a couple of years to where it's inconsistent in starting, sometimes takes a few cranks... but how would it produce a noise that goes away after it warms up?

 

[l3n0x]

Sounds like a stone jumping around in the sliders

 

[AlpineAccess]

While I'm inclined to agree with others, this actually does sound like an exhaust leak to me. If it's louder after replacing exhaust components, I would start it while the vehicle is cold and spray the exhaust connections with soapy water.

A noise that goes away when warm is due to metal heating and expanding and closing up the gap. This would be a very significant exhaust manifold leak, I'd look at the donuts on the cats first.

If this doesn't do it, buy a cheap engine stethoscope or even a piece of conduit or something and start hunting the noise down.

 

[128keaton]

Sorry to necro, but did you ever figure this out? I’m dealing with something similar, but it comes and goes. Right now, I can always hear it if I rev the engine, starts rattling when the engine revs down.