I agree that usually these units do require extensive cleaning. I do have the engine power washed ever two years, just to knock off road dust/debris/crud that may have landed
! At that time, I also have the tech spray down from both sides as best as they can hit them, the radiator. (In between these times, I'll also spray form the outside with my normal hose while washing the coach. But I do use soft water while doing this, to minimize hard water depositing on the fins.)
One caution, I had a shop that I've used a few times do one of these engines cleanings. And a newer tech was assigned the job. He did OK on the engine spray down, but dang if before I could stop him he had not hit the outside radiators from the outside with a full force pressure washer... I ran out to stop him, but the damage was done, and some of the exterior fins had been slightly bent. After getting the Shop Manager out with me to review, I elected to not attempt having the fins straightened with a radiator like brush. (The fins were not too badly bent, and I was frankly more concerned about additional damage.)
The tech learned a lesson, and I still see him when I come into the shop form time to time. And the Shop Manager rather begrudgingly, did not charge for the engine/radiator spray down.
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I share that little story, to help others have an 'upfront' talk with any tech that they may ask to spray down their engine and radiator as maintenance - to dial back the pressure
!
Best to you, and all,
Smitty