2008 vw jetta low temperature on gauge

[s900t8v]

hey guys

my 2008 vw jetta is showing low temperature at highway speed around 65-70 celsius, with idling it will creep up towards 90

assuming this is a thermostat

anyway to figure out which one?

thanks all for any advice

cheers

[Umai Naa!!]

FSI Turbo?

Thermostat is pretty common on these.

[s900t8v]

FSI non turbo - jetta 110kw

looks like from further investigation that there is only 1 thermostat on the BVY engine at that it is a whole housing and thermostat assembly I need to replace.

from waht I can tell there is no in line thermostat in the BVY engine.

I doubt that its from the coolant temperature switch right, seems to be that at idle it will creep to 90 degrees, on highway 65-75 degrees (double checked the coolant temp with the secret menu digitally and it fit with the gauge) its not flicking between 0 and a higher reading that would suggest its bad..

also there are no check engine codes .

GATES TH40187G1 Thermostat, coolant | eBay

this is what i was gonna buy, gates usually pretty good...

looks like easiest way to drain the coolant is by pulling the coolant temp switch, do you reckon I should replace looks like I can get one for about $4 from china

Engine Coolant Water Temperature Sensor For VW AUDI SEAT SKODA 06A919501A | eBay

[JustCruisn]

Mine does the same. Has been for a long while now about 35,000km. I have not seen any issues other than the display not at 90.
In summer it is mostly spot on, never reads over 90.
I figured it can wait for the next timing belt & water pump change, about 4 years to go.

[s900t8v]

well it tends to be as low as 65 c on the highway which is pretty low... makes me think ti would be affecting fuel economy/performance because the car probably thinks the engine isnt warm so the timing would be more retarded and the fuelling a little richer to facilitate warmup

if thats the case then its probably affecting engine wear as well

[Umai Naa!!]

Absolutely.

The ones I've seen, took forever to warm up.

[s900t8v]

is there only 1 stat on jetta?? its the integrated unit like i posted?

[Umai Naa!!]

Yeah, that one looks correct.

It's tucked down behind the alternator. Fun job.

[s900t8v]

haha I bet it is!

cant be more fun than doing a saab 900 crank pulley (down against firewall)

[Stuwey]

It's tucked down behind the alternator. Fun job.

That's why mine has been running cool for about two years

I guess I really should get on with it

[s900t8v]

Can someone confirm. Is there only 1 thermostat on this model?

[Umai Naa!!]

Correct.

[Cheezel]

I have an OBD reader in my TDI, and it's interesting that the gauge shows a solid 90 for a coolant temperature the computer is reading from about 75 up to about 105 (long hill on the freeway). So, if you're reading about 70, it could be quite a bit lower.

[Umai Naa!!]

The guage doesn't entirely correlate to what the coolant temp is actually doing.

[JustCruisn]

The gauge is "weighted" so it will show 90 when in the nominal range.
I have found it will sit at 90 until temp goes over 105, the alarm sounds shortly after that at which time a tow truck needs to be called.