So the R4 has been standing for 3 weeks, with no overheating issues before. It emptied the expansion bottle at one occation though, and it has had some problems getting enough heat from the heater. Today was it's first run and after 1 hour on the highway at 85-95 km/h the overheating light came on. I then slowed down and at a rest site I bled air from the system, and got home without further incidents. - The head gasket seems to be fine - It doesn't leak - The heater now works better - The radiator is not overly gunked up in dead insects and what-not - The radiator and thermostat is a bit over one year old, and should work fine (it's a 75 C thermo I think). So: Would you think I just should keep on driving, or pull of the heater matrix to look it over? Or maybe do something else? I've heard that the waterpump 'wheel' might turn with a cold engine but loosen at speed with a warm engine.