I took the MK2 on a winter road trip to London today.
The co-pilot (15 yo) pointed out that we were over heating - up to 100 degC, but I noticed that the fuel gauge was also off scale… Voltage regulator?
The problem went away after coming off the M3, but happened again on the way home … intermittent voltage regulator?
The gauge and the stabilizer could be culprits, but the true test was whether you had a boiling over condition. Might also be a good time to get a new cap of 7 pounds of pressure (what I use). New hoses, new heater controller, etc…