Nothing to worry or what you think? At least engine is running and brakes have air.
Scania gauges 
Nah…
show that to any deisel fitter worth his salt and they will utter those immortal words
Let it develope
Brings back memories from my Scania driving days!
excuse me, Do you know there is hot water and steam pouring out the engine bay?
Yes you have either
run out of diesel , got low coolant and overheated your engine
Or
You have a wiring fault, Being a 3 series I would check the earth straps from chassis to cab at the front cab mount area first
The fact that you’re doing 80 kph and holding a solid 1600 rpms without your motor shooting trajectories in all different directions would tend to suggest that you have an electrical problem. I would suggest shutting the truck down for a minute, then start it back up. The gauges should reset that way.
a bit of polish wouldnt go a miss either,
Discopete:
You have a wiring fault, Being a 3 series …
And we have a winner. When you knock plexiglas on front of gauges they show correct values (at least some of them will work or show rational values 
) As said, typical Scania gauges
Btw you forgot to say there isn’t any oil pressure 
Bit of polish would have been nice but this is/was companys spare truck and was used only occasionally by different drivers so nobody was looking after it. I did clean it up after this trip but that’s part of other story.