Actually the "oil from slobber tube" being pulled into the cooling package was universal to all diesels with open crankcase ventilation.
But, let's address the OP's issue.
VERY easy to check for blockage (BTW, the air flow blockage would not be in front of the radiator, but in front of the CAC (Charge Air Cooler) which is the first thing in the air flow.
Access the top of the engine (bedroom or closet). You will need to be able to look inside the fan shroud/between fan blades. With a strong flashlight, look in the center. It will be clean (the blades "sling" the dirt to the perimeter). Now, look at the perimeter- particularly the lower perimeter and make sure the fins are equally clean.
If not, Simple Green EXTREME (formulated to degrease aluminum airplanes so will not harm the aluminum CAC)and a garden hose/garden nozzle should clean it up unless it is really plugged. THIS NEEDS TO BE DONE ANNUALLY ON A REAR RADIATOR COACH!!!!!
If that is not the problem, then absolutely the first "repair" is to replace the thermostat(s). They are a wearing item. Some Cat 3126/C7's have two thermostats-- in the same housing. Be sure to get the correct gasket. Taking your engine serial number to any Caterpillar dealer should get you the proper parts.
Other thing to check is the water pump belt. It is NOT on an automatic tensioner, but is a small V belt that drives only the water pump. Check it from under the coach-- driver's side of engine. Front of engine (toward back of coach). It has a manually adjusted idler pulley.
Let us know what you find.
