OP,
Yes, 225 is high temp; average temps you should be seeing are around 185-205, depending on ambient temps, climbing hills, or load being pulled. With my C7, I see around 187-193 flat land and maybe 205 on steep/really long grades. Just for comparison sake.
Given you have a 2007 Discovery listed in your stats, I'm going to presume you are on a Freightliner chassis. If that is the case, that link Skip provided is a good source of info, specially relating to what debris can get sucked up into the radiator/CAC area. Leaves and trash are often found in the space between those components. Unfortunately soap and water is not going to remove that material.
Other guys mentioned washing the radiator/CAC and this is true as well. This may be an easier/less costly first attempt at decreasing your temps, if a blockage is what is your issue. However, this may prove quite challenging as just washing from the rear of the coach is not enough. The CAC should be cleaned from the engine side where the fan is...there is your challenge for sure. I use the purple simple green for this cleaning, not the normal green version.
Now something not mentioned so far and is another consistent reason for plugged fins of the CAC/Radiator; oil mist from your crank case breather tube, often referred to as a "slobber tube".
A common reason why excessive oil mist may be occuring is due to an overfill of the crankcase engine oil. Back then, the information widely used was that the C7 motor took 22 qts of oil, later, that number was reduced to 19 qts. If a dealer/shop is doing the oil changes, it is very reasonable to think that they may have added too much oil.
So besides reducing the amount of oil in the crancase to 19 qts, another practice is to add an extension to the slobber tube to either exit the side of the coach (passenger side) or to exit under/past the radiator to the rear of the coach. If you add this extension, which is highly recommended, make sure there are no valleys/dips for oil/water to accumulate in, this extention need to run downhill the entire way to ensure breather ability.
Here is another thread regarding slobber tube extensions:
https://www.irv2.com/forums/f124/slo...ons-75260.html
One last thing I can add is a driving tip, specially for hill climbs. When climbing a hill, a lot of guys recommend not lugging the motor by manually lowering your transmission gear selection. The goal in this scenario is to maintain engine speed around 2,000 rpms or so. This will increase waterpump speed and coolant flow. This could be something to practice after you fix whatever is causing your current high temp situation.
Overheating Issue
Linear Mode
