Hi guys, what makes the cracking sound on a diesel engine?
When it is cold, it sound lowder for a while then the sound get smoother once you get going. There is a noticeable smoothing out of the cracking sound after a mile or two.

Just to know

 

When cold there is a temp switch that advances the pump timing by a couple degrees to help with starting. It shuts off around 110 degrees.

 

I see, that is why in the summer the sound is not as loud.
What makes that crackcrarck sound?

Thanks

 

It's combustion knock. It gets louder the more advanced the timing is. After setting my timing up to 8* it almost sounds like a P/Stroke in the morning.