no.
100C is fine on a 617
if it's going up to 120, then you are experiencing problems.
how is the cooling system in your car? when was the last time the coolant was flushed?
what color is the coolant in your car?
what radiator cap is on your car? what pressure?
what is the mixture of coolant to antifreeze in your car?
did you mix with tap water or distilled water?
in those extreme temps, I'd be sure not to use more than 35% antifreeze 50/50 is horrible for high temp driving. pure water is better, but it needs the antifreeze for it's antiwear and plastic conditioning.
you say it does it with your a/c on up hills... what refrigerant is in your a/c system? has it been converted to 134 or is it still (hopefully!!!) running 12?

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!