My turn to guess:
1. Clogged radiator.
2. Leak in the system, Are you losing coolant?
3. Was the proper thermostat (rated (i.e.opens at) 88C....I think)
installed?
On the highway, my 405 Mi16 stays at approx 90C....the cooling speeds do
not come on. In stop an go traffic, my temp goes quickly to 92C and fans
come on and off as they should.
Mike Savage
Boston, MA
405 Mi16, 112k miles