Check your aux fans
Check to see if your auxilliary fans (electric in front of radiator) are cutting in when they're supposed to. They activate on low speed at 100c, high at 107c. They're also activated by A/C pressure - and should come on quickly after turning on the A/c at idle (especially in Phoenix). If they're not coming on - come back and the experts on this forum can direct you further.
1995 E420 Brilliant Silver 67k