273 Overheating
While hot and running,, if you have a heat gun,, check the temps of the radiartor INLET/OUTLET fittings, (not hoses), there should be 30* - 50* diff between the two..
If no heat gun,, hot and running,, touch the front surface of the rad, (I use the back of my knuckles) about mid way,, all across the rad,, if you find any cool areas,, those are plugged tubes not flowing hot water..
The larger the cool areas,, the bigger your blockage..
hope it helps