I agree....I replaced my radiator after having the same problem. But I suggest a quart or so of CAT Radiator conditioner. I had a CAT backhoe that conditioner was used twice a year for 7 years. Another Cat backhoe bought after mine had radiator problems and conditioner WAS NOT USED. The old backhoe never got hot and anti-freeze looked new after 7 years. The new hoe had to be flushed a couple times...the old one looked new inside the water pump when replaced. I use conditioner in both mine.
1983 300SD 343K everyday car
1983 300SD 285K from junk yard-tooks parts from deer car- runs great. Brothers car.
1984 300SD parts car-Hit deer
1979 300D 175K non-turbo "Doctor"
1979 300d parts car