Noise at 2000-2200 rpm

[a80crewza]

Got an annoying noise from my 1HDT sounds like this except between 2000-2200 rpm, been like this for years.

https://m.youtube.com/watch?v=Gvu6JBMBJNs

Any ideas?

Cheers.

[mudlva]

I would be looking for rattles around fan shroud
And exhaust pipe heat shields. Sounds like external vibrations rather than internal cause if a piston or valve was that rattly it would destroy itself in the process.

Or just turn the radio up a notch or two

[DieselBoy]

We have a Troopy in Aus with a 1hz in it.

It's got a similar sort of harmonic vibe at those revs when not under load. Put it under load and it's not as pronounced.

It's a harmonic vibration produced by the rotating parts of the engine vibrating at a particular frequency at a certain rpm. It varies from motor to motor, depends on how well balenced the crank, fly wheel and other assemblies of significant rotating mass are. The harmonic resonance can set all sorts of things in the engine bay off, the snorkel and front bash plate being good examples.

Our 1hz also as an annoying rapping/ticking sound at about 2500rpm whether under load or not. Lots of forum googling turns out people have rebuilt entire motors and had warranty repairs done to no avail, the rapping noise is just what they do after a while apparently.

[a80crewza]

It's got a similar sort of harmonic vibe at those revs when not under load. Put it under load and it's not as pronounced.

It's a harmonic vibration produced by the rotating parts of the engine vibrating at a particular frequency at a certain rpm.

Thanks, thought it might be the harmonic balancer but this makes sense. Would I need to do something about this long term or is it just what these egnines do with age?