I've my MK1A for 10 years now
& have changed the coolant a number of years ago with no issues. Yesterday I was driving to a show. Weather was very hot. After about 50 miles the temp gauge shot up into the red having been sitting in the middle for all the journey up to that. I quickly pulled over & switched off. Was driving at about 50mph at the time. Radiator did not feel very hot & coolant in the bottle was just above max. No fans running. I restarted the engine & slid heater to hot. Immediately the temp returned to normal. I drove on the last 10 miles to the show with the heater on & no issue. I tested turning off the heater & immediately the temp started to rise.For the journey home I put the rad fans
& the engine bay fan running continuously & gauge sat just below the centre point. Engine temp didn't rise & weather was seriously hot & hot inside car with heater on. About 5 miles from home I turned off the heater & the temp gauge didn't budge.I've searched for this issue on the forum
& it looks like it could be an airlock or possibly the thermostat,Anyone got any suggestions.
Had trouble with a faulty gauge a few years ago but when this reacted when I put on the heater, it's probably OK.Tim
