Engine heating up *70 kph up

[dr. d]

my guess is, you're overheating, causing your coolant to boil away. and not the other way around.

i would inspect the radiator fan or the aux fan.
just because they're rotating, does not mean they're working fine. they may be rotating, but not fast enough, resulting in under-cooling.

check your coolant overflow cannister, po. if it's level is low, then you're overheating. if it's not low, then you might have a little leak, that becomes large when the engine is running. (a rule of thumb that has many caveats.)

one other possibility, is that your radiator is so dirty in and/or out, that proper heat exchange is already severely compromised.