Out of lurk mode and need help.

The facts (92 500E):

-New hoses, radiator (Behr), water pump (Graf), thermostat, MBZ coolant, fan sensor. (This was all done because I had the front of the motor apart to fix a power steering leak.) This work was done 6000 miles ago by me.

-Electric fans are working properly (low speed with AC, high speed at 100C). AC working OK, could be colder but it works.

When car is under load uphill (60mph+) for more than 5 minutes, the temp will climb above 100C. It did not do this before.....I've noticed it much more now that outside temps are 80F+.

Thoughts:

The only thing I have not replaced is the fan clutch and reservoir cap. But if I am only seeing high temps at freeway speeds, then the clutch should not matter. Right?

Could an air pocket have survived in the system for the last 6000 miles?

The gauge seems accurate; when it reaches 100C, the aux fans switch to high speed.

Thanks in advance, knowledgable input appreciated!

__________________
Gregg

'92 500E (Sold)
'07 E63 AMG (Sold)
'10 S550