if I let my 1995 s320 idle for more than 20 minutes it runs hot between the 100 and 120 degree range but while I drive it runs a little over the 8o degree range what could me be the problem

Check your aux fan operation,cooling fan clutch & thermostat I'll check thermostat first.

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MB STARS Master Guild Technician,17 years MB tech
14 years independent shop owner

Your engine temperature actually seems quite normal. It is normal for them to run hot when idling. Anything over 110 I'd worry about.

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2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)