The engine is having cooling problems. On the highway it is running to hot. When I slow down or in city traffic the temperature is ok. The expansion tank is also running over all the time.

For our planned Africa trip I wanted anyway a better cooling system so I replaced the core of the radiator for one with twice as much channels. This improved the cooling just a little bit.

Later I changed the radiator cap. This stopped the expansion tank from spilling cooling agent. I also changed the thermostat, viscous coupling from the fan and water pump. This improved the cooling even more but not enough.

The ignition was set properly but it is still to hot. I'm still figuring out what to do to get the cooling right.