My 81 300SD always ran in the 100* range in ambient temps above 95*. The 82 was running the same temps until I replaced the radiator with one from a 85 300 SD which has an almost 50% thicker core. Now it will only get up to 85-90* on a long pull.

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1971 R600 Mack toterhome (SuperDawg)
99 NU-WA Snowbird 34+2 SE 102 5er
If it's not diesel, it's not in my stable!
53 F100 617.951/auto
95 Dodge 3500 Cummins/5 speed service truck