A quick look at the serpentine belt when this first happened didn't seem to be a problem. It was moving. But I will look closer since a year ago I had to replace the alternator and of course that involved messing with the belt.
Tranny fluid level was good when I checked it after the problem occurred. Coolant level was checked a couple of weeks ago and the level was good and it tested and looked good.
I now vaguely remember the location of the test port. Thanks for the reminder.

__________________
Len
'59 220S Cabriolet-SOLD and living happily in Malta
'83 240D 351,500 miles original owner-SOLD
'88 560SL 41,000 miles - totaled and parted out
https://sites.google.com/site/mercedesstuff/home
'99 E300 turbo 227,500 miles
'03 SLK320 40,000 miles - gave to my daughter
'14 Smart electric coupe 28,500 miles
'14 Smart electric cabriolet 28,500 miles
'15 Smart electric coupe 28,000 miles