Scania r620 running hot

Either the thermostat or perhaps electric fan are my first thoughts. I assume there's no signs of distress from the water pump, but if no leaks or noises then that's prob ok

It could definitely be the transmission fluid. Check the fluid level when the car is running and up to normal operating temp. You should have a mark on the dipstick saying "hot-full mark". That is exactly where your fluid level should be. Make sure you put in the correct fluid type, and that you do not overfill it. If it is not shifting like it should, then it could be time to change out the transmission filter. Not a difficult job, and a lot cheaper than a new tranny...

Possible EGR valve

engine temp is higher than normal, temp will increase when engine is under load usually climbing an incline, it may take a considerable distance of level driving to reduce temp

Most systems work this way: temp sensor on engine sends a signal to the computer which in turn sends signal to blower relay that then sends signal to the fan.
Any problem along the way, and the fan won't come on.

sounds like the radiator fan is not coming on. possible cause is the cooling fan switch or the cooling fan relay. worse case senario is the cooling fan is bad

check your coolant level, its may be low causing the fluctuatiion also the loss of heat. if its ok replace your thermostat its not regulating tempature right

has the water pump been changed recently? The water pump on a 4.6L 2v and 4.6L 4v look the same but are different

ast the halfway mark isnt overheating. Any bike will rapidly increase in temp when stopped or moving slow. the fan will not kick on until the bike reaches around 220 deg. Im not sure how that relates to your gauge as Im assuming you have just a C and H with a few lines between., but Im sure its near the upper range of the gauge. I would think your bike isnt hot enough for the fan to kick on. I would let the bike get a little hotter and see. If the fan hasnt kicked on when the needle reaches the upper portion of the gauge, take it for a quick spin to cool it off, dont just shut it off as that will actually create hot spots within the motor, and then consider either the fan is faulty, or the relay. You can pull the fan and test it with a 12 volt battery. One hot, one ground. If it works, it must be the relay. I doubt the stall has anything to do with the bike running warmer, unless it is truely overheating and you have antifreeze pouring out of it, then it might be. You might just be in need of a good carb cleaning.

need to know how to change the fuel pump, do i have to drop the fuel tank or can i get to it from under the back seat