Alltrack operating temp

[Hillbilly]

Ok

So it happened today, quite strange behaviour and probably one for the mechanic but I thought I’d pass it by you experts anyway!
So outside air temp 13 degrees. ~30 mins drive time on freeway at 100km/p/h.
Oil temp running at approx 85 degrees
Temp gauge oscillating between 75 and 90. Literally would get up to 90 and then drop again?!?! Also noticed it dropped when I went down a hill!
Anyway I normally deactivate the start / stop but when I reached an off ramp I decide to see whether turning the car on and off effected it. So activated start stop and when the car turned back on the temp gauge went to 90 as it should and stayed there?!!!?
Oil temp digital read out still at 83-85
Any ideas / clues based on what I’ve shared?!

Dont worry about oil temp I wouldnt ever have a clue what it is. Its got oil in it let it do its job.

Sounds like an air lock in the cooling system

Water temp can be problematic Read reply 2 and do what I said and see if it gurgles and farts. As I said there is a thermostat above the tranny which has been known to give problems and I bought one and havent used it. as burping fixed it.

I have sold the car and still have the valve which cost $50 from Lithuania (dont know cost here) and easy to fit it thats the problem. Is instructions on Youtube
Part no is VW1KO 121 113A if you want to check

[Mc_Gusto]

Thanks hillbilly

So do I take the coolant lid off, listen for burping and leave off overnight?

What does it mean if I hear burping?

[Hillbilly]

Thanks hillbilly

So do I take the coolant lid off, listen for burping and leave off overnight?

What does it mean if I hear burping?

Turn motor off loosen coolant bottle lid Dont take it right off for a start as is pressured a bit Wait for a while and see if it burps and if it does means it has air in system. Leave it off over night Cured mine.
Next step would have been to change that thermostat.. I was going up a steep long hill and water temp showed about 60 so alarm bells started ringing in my head LOL

[brad]

Thanks hillbilly

So do I take the coolant lid off, listen for burping and leave off overnight?

What does it mean if I hear burping?

It means there was an air lock and the air is burping out of the system.

there are 4 possible causes to your symptoms.
1) airlock
2) thermostat
3) faulty water temp sender
4) faulty gauge
5) something else ;-p

[Hillbilly]

It means there was an air lock and the air is burping out of the system.

there are 4 possible causes to your symptoms.
1) airlock
2) thermostat
3) faulty water temp sender
4) faulty gauge
5) something else ;-p

Yep first two are recurring in the Passat especially if anything done on the cooling system

[Mc_Gusto]

Well I did the test when I got home tonight, loosened the coolant lid and then removed fully

No burbling, burping or farting. Wasn’t sure how long to listen for but there definitely didn’t seem to be anything of said description.
That said the temp gauge was operating fine (as it often does) and so I’m wondering if I should do the test again when it next plays up?

[Mc_Gusto]

I may not of left it long enough - roughly how long should it be before I hear a burp?

[Hillbilly]

Just leave it off till the morning as it cools down Thats what i did just loosened it and left it with the bonnet up so I didnt forget to tighten it . I didnt bother to listen after the initial burp

[Mc_Gusto]

Ok will give it another crack after next drive. Thanks heaps for the help by the way!

[Mc_Gusto]

Well I don’t think it’s an airlock issue. Can’t be 100% sure but ive left the cap off overnight and it doesn’t seem to have cured it.
Seems to occur mostly on cold days and only on the first time I start the car. Ie. if I run the car later in the day or switch the ignition off / on it seems to recalibrate to the standard 90 degrees Celsius

Weird and annoying but not a major issue really..when it’s due for a service I’ll see what the mechanic has to say I guess