Sorry. Didn't read the last post.
If you can run for so long within good temp and then shoot up when you reach your destination (clue- now going slow, stop and go), then your circulation is probably good. The problem in in heat transfer (ie. radiator) when going slow and while stopped. The things that help heat transfer are a good pump and a good fan.
I agree... check the fan.
'05 E320 CDI - 86,000 miles
'86 300SDL - 360,000 miles
'85 300SD - 150,000 miles (sold)
'89 190D - 120,000 miles (sold)
'85 300SD - 317,000 miles (sold)
'98 ML320 - 270,000 miles (sold)
'75 300D - 170,000 miles (sold)
'83 Harley Davidson FLTC (Broken again) :-(
'61 Plymouth Valiant - 60k mikes
2004 Papillon (Oliver)
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