Komatsu PC210-10 "flapping" noise from exhaust stack. What could it be?

[George]

Looking for some advice here. I've got a Komatsu PC210-10 that recently started making a weird "flapping" or fluttering noise coming from the exhaust stack, especially when the RPMs go up.

The machine still runs fine, no major loss of power (at least not obvious), but the sound definitely wasn't there before, so I'm trying to catch it early before it turns into something expensive.

What I've Checked So Far

• No visible cracks on the exhaust stack
• No warning lights on the dashboard
• The engine starts and idles normally
• Noise gets louder under load / higher throttle

 

[Robert M.]

In my case, that "flapping" sound ended up being a loose or partially broken internal baffle in the muffler. At idle, it sounded normal, but once I throttled up, the exhaust flow made it flutter like a tin sheet. No codes, no power loss, just an annoying noise.

 

[Majidadi84]

That "flapping" from the PC210-10 stack is usually one of these:
1. Loose exhaust flapper/rain cap - Worn hinge or missing counterweight flutters with exhaust pulses.
2. Cracked flex pipe/bellows - Leaks cause a flutter sound. Check for soot around joints.
3. DPF/EGR backpressure - Clogged DPF or bad sensor on Tier 4i models can make it flutter at idle. Scan for codes.
Quick test: hold the rain cap at idle. If noise stops, it's just the cap.
Same issue pops up on other RB Global brands like Deere 210G, Volvo EC220E, and Cat 320s. Post any codes you're seeing.