CAT 420D IT (A little smoke?)

So far I have about 15-20 hrs on this new to me backhoe.

This week I dug a 400' ditch, buried (1) road pipe.

I have made sure to check fluids everyday and even replaced the rear diff fluid with the additive which quieted the brakes.

I have checked for blow by from the vent hose down by the pan (it was slightly wet but no smoke. I opened the oil fill cap and no smoke or spitting oil...

The only time I have any smoke from the pipe is when just getting on accelerator (black puff)


Yesterday I finished up for the day after digging through a little rough spot in the ditch (granite/petrified clay).

I left it idling while my wife and I went to look at the progress. It idled for about 10-15 minutes at low rpm and started sending a continuous line of light blue smoke.

Does that sound normal/bad?

Are there any breather lines or filters that could get clogged or need service?

Thanks for any help
Daniel

CAT 420D IT (A little smoke?)