Are you absolutely sure that there isn't too much air in the system(An air pocket) ?

When I refill the 300D cooling system I take the upper radiator hose loose at the radiator and finish filling that way then put it back on fast.

First time I ever refilled a 300D I did it through the tank cap only and it ran too hot. Let it cool and filled through the hose...problem gone.

Your car running at 100 C doesn't seem too bad, but if it goes above that ...

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Diesel-guy