ED30 Fluctuating Temp Readings

[CChambo]

Hi Guys,

I brought a 57 plate edition 30 gti this Saturday as a replacement for my very rusty mk5 R32!! 

On the drive home on Saturday I noticed the temp gauge seemed firm at 75 degrees  (compared to the R32s 90) but I wasn't sure if this was normal or not! But after some research on the forum it seems it may be caused by either the main thermostat or the coolant temperature sensor.

I decided to monitor it on the drive home today and found that, it warms up to 70 in about 3-5 mins but then seems to stick there for a bit.
It then warmed up to 90 after a further 3-5 but whilst in slow town traffic!
Dropped down to 80 as I started picking up speed, but increased back to 90 as I got back into slow moving traffic!
Once sat at a steady 50-60 mph it dropped to around 75-80, fluctuating depending on my speed
As I got back into town traffic near home it went back up to 90 again!

I was wondering if from the description anyone would be able to pinpoint or give suggestions to the solution!

Cheers,
Cam

[GrayMK5GTI]

I had this exact problem. Was the thermostat. Pig of a job to replace though 

[CChambo]

I had this exact problem. Was the thermostat. Pig of a job to replace though 

Thanks for the quick reply! Did you end up changing it yourself or getting a garage to do it?

[pudding]

Yeah as above.

Not that bad a job to be honest.  Jack it up, under tray off, alternator out, throttle boost pipe off, all the dump valve stuff off, some stuff above the filter housing off, and then it's accessible.   Took me about 2 hours.

I also replaced the temp sensor whilst I was there.  Imagine doing all that work thinking it was the thermostat, but it was the sensor all along.  Do both is my advice