[Guy]

Thank you. I never thought of the hard water aspect. We have not needed it often, but on one occasion on Hwy 17 From Phoenix about Bumble Bee, it was high ambient, combined with altitude and no pull outs to cool down that worried me. Ended up aborting and heading back down the hill and taking Hwy 10 east, instead of going up to 60. Never had a problem in Tahoe, or the California Sierras, or Continental Divide  as there is plenty of opportunity to pull over and cool down.

I thought I might  have radiator issues that are limiting cooling capacity. I put my 39 dollar bore scope ( thanks for the tip Richard ) and took a good look after lowering coolant level . Did not see anything out of the norm. Tubes look great. Radiator fins are now super clean.

I do know that between my Digi-Panel, and antique dash gauge, the coach can go from 190-195 to spitting out coolant in a heartbeat.  We call this the baker Grade Las Vegas episode.    Not something I ever want to have happen again.

I am open to any and all suggestions. In the mean time we will plan our trips around ambient temps and altitude.