I'm still not able to find that glow plug on my tractor. Is it possible that it is really an option? But I suppose if it was an option there wouldn't be this light indicator. In my case there is that light so I think there should be also a glow plug somewhere.
That thing which I marked is not a glow plug. Today I managed to take it out and thats what it looks like:
When I had removed it, a coolant liquid started to leak.
Also I have found this:
It looks like heating system for an air. It is connected to the air pipe from an air filter. I didn't check if it works correctly. I'll do this tomorrow.
So could anyone tell me where that glow plug should be? In which part of an engine should I look for it?