My 89 240 was occasionally sending the temperature gauge into the red while running the air conditioning this week. Not real often and turning the air off would eventually allow the gauge to return to near normal. I pulled the radiator today and holding it up to the light showed about 50% of the cooling fins blocked with vegetation, animal hair, bugs, dust/dirt, etc. I used a water hose at home on the back side of the radiator followed with compressed air and then a small brass brush to remove as much material as possible. It was necessary to do it twice to get everything out. I then used the hose on the air conditioning condensor and dislodged a lot of "stuff" from it.
People have talked about cleaning their radiators out using the high pressure car wash wands, but those things can have enough pressure to blow the cooling fins right off of the tubes and bending the remaining ones over to restrict air flow.
At any rate when the problem presented itself I thought I might be in line for a new 3 row metal radiator replacement, however, after restoring airflow to all areas of the radiator the gauge needle rides right on the normal half way point in the same situations that would have put it into the red previously.
Evidently the material that ended up clogging the face of the radiator passed right through the air conditioning condensor (which has larger spacing) and was not apparent in a visual inspection after removing the grill. So if you are experiencing a borderline cooling system cleaning the radiator's cooling surface may be enough to put you back in the normal range.