That is fine to do for preventive maintenance, but the initial cleaning is best done outside the car as was suggested. Keep the nozzle at least 12" away from the core.

I wouldn't do it.

It's nearly impossible to keep the nozzle perpindicular with the face of the radiator while it's in the vehicle...........the risk of bending fins is quite high.

I don't think I would go to the trouble of removing and reinstalling an old radiator. If it's degraded enough to go to the trouble of removing it, it's probably due for replacement anyway.

I'm glad I just replaced my 240D radiator, I drove across SoCA on I-8 this afternoon (about 110F with some very long 6% grades), it stayed between 85-95C the entire trip.

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.

__________________
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