Ok, finishing the story for completeness - I've replaced both of these bypass thermostats today and now my temp goes from ambient (currently 5c) to 90c on the gauge in 5 mins flat and then is rock solid.
If you think you have problems you can remove these bypass stats really easily and just test them in a pan of water.
If you take them out try blowing through them first of all at normal air temp. They should be shut. They should start opening at about 77c and be fully open at 88c, co-ordinating with the main stat opening.
Hi guys, I hope you can help with my 'temperature problem':
I live in The Netherlands and have a 06-2005 AXX DSG mk5 GTI.
My temperature gauge reaches the 90 degrees celcius quite quickly, but I noticed it often points just a milimeter in front of the centered 90 degrees (so say 85 analog degrees celcius).
So I took al look in my climatronic, option 19.2, to see how many degrees my coolant temp digital is. I also used vcds a few times to monitor this temperature.
Digital readings say my coolant temp is around 74 degrees celcius.
I found out that the analog meter stabilizes at 90 degrees when in real life it is between 75 and 108 degrees celcius (stabilizes because otherwise people would get 'scared' seeing the fluctuations all the time).
Digital I can only get 80+ degrees celclius coolant temperature when I do a spirited drive and let it run stationary / traffic jam after that drive.
No real difference between city driving and highways, it just reaches around 85 degrees on analog meter within reasonable time (15 minutes city driving!?), but in real life (digital) this is only around 74 degrees and it won't get significantly hotter.
I think it should also reach around 90 degrees on accurate digital readings? (healthier for the engine?, because my oil temp is also under 90 degrees celcius because of this)
So one of the thermostats must be faulty...
Do I need to replace the MAIN-THERMOSTATE? Or is this one of the two (do I have two?) small thermostates?