Hi All. A while ago, after years of the temp gauge running at 90 solidly (once it had warmed up that is!), I noticed that the gauge dipped quite suddenly to about 70-80 but then returned to its normal 90 just as quickly, this was fairly unusual as it normally just stayed on 90, but it didn't do it again for ages so I didn't think too much of it. Recently, it has started doing it more often so that now it happens on most longer journeys. The car warms up from cold and the temp gauge behaves normally until it gets to 90, after it's been running at 90 for 10mins or so, it starts to fluctuate intermittently, although it never goes above the 90, but the dips have become bigger and recently it has gone down to 60 or so before coming back. It sometimes feels like the heater is less efficient when it is doing this but I don't know if this is just me. I suspect it need a new thermostat or could it be the temp sender. Are these easy enough DIY jobs on a MK2 1.9TDi? and if so are there any guides with photos so I know what to look for? Anyone experienced this or have any advice?