A thermostat question

[missymckay]

Just a quick question that I am hoping someone can answer. I think I need a new thermostat (main one) as the temperature has started to fluctuate between 80 and 90 degrees. It doesn't do it all the time but will do if I have had the air con on or occasionally driving around. I will be changing the coolant temperature sensor next week but I was wondering if there are any problems that may arise if I don't change the thermostat. Does it really need to be at 90 all the time?

Many thanks

[GrayMK5GTI]

The engine doesn't get to full running temp with a busted stat, the ECU tries to get the engine warm by adding extra fuel so your MPG will be worse

[missymckay]

Thanks

Sent from my SM-G900F using Tapatalk

[rich83]

Mine reads 90 on the dial but never exactly 90 on the polar FIS

[Shoduchi]

Mine reads 90 on the dial but never exactly 90 on the polar FIS

What Rich said.

I have Polar FIS and the dial reaches 90ºC when the engine temperature is 75ºC. If yours goes lower than 90ºC, the real temperature should be around 65º-75ºC. I have my DSG stat busted at 75ºC, just enough to reach the correct temperature in the dial but it only truly reaches the 90ºC when the car is stopped. Found it with the Polar FIS.

I already have all those parts ready to be fitted (stats and sensors), just need to arrange a date with my mechanic.

[dazza]

Like Shoduchi said the gauge has a massive range. My gauge was on 90º but polar showed 75º. Now the main stat has been changed coolant temp is 90º/94º. Once the needle is at 90º it should not drop, the car warms up much quicker than before.

[missymckay]

Cheers, I have booked it in to be done in a couple of weeks 

[rich83]

Just checked and my gauge reads 90ºC... but the polar only reads about 80-82ºC.

Worth changing it?

[fab5freddy]

Does the gauge drop off 90?

Might just be coolant temp sensor, as opposed to the main stat, I'd leave it a while and monitor it for a week or two before diving into a new stat

[rich83]

no... gauge always sits at 90 once hot

[fab5freddy]

Leave the main stat alone then, not a cheap fix, my polar gives consistent 90-94 as Dazza's, could be a faulty coolant sensor, easier and cheaper fix I believe

[GrayMK5GTI]

Leave the main stat alone then, not a cheap fix, my polar gives consistent 90-94 as Dazza's, could be a faulty coolant sensor, easier and cheaper fix I believe

THIS ^^

You've got enough expense coming your way with Mechatronics & Steering rack @rich83   

[rich83]

f*cking tell me about it! 

[dazza]

My oil temp is a lot higher now. How would the lower coolant/oil temp affect the engine and DSG??