Re: Unexplained coolant leak
With the recent warm weather older radiators are getting found out. Mine started getting too warm at town speeds, the fan would cut in and not get it back under 102C until I could speed up and get more airflow through the rad. so I changed the radiator for a new (copy) version. Problem solved. I don't know if you noticed what the temperature display was telling you, but it could be that your system boiled, blew itself out through the expansion tank (and hence the coolant on the right side, same side as the blowout pipe from the expansion tank). some then got sucked back into the system when it cooled, emptying what remained in the expansion tank. Maybe the fins on your rad are bent obstructing flow, maybe the thermostat is not opening fully - but they are pretty reliable. I'd look at the state of your radiator and decide based on that. Could also be that the pressure cap is letting go at too low a pressure, but that's unlikely. A few ideas for you anyway.