Being driven round the bend with this.

2014 (facelift) with CR170 TDi and DSG. 320,000km (or 200 ish miles)

When I originally got the car, coolant temps were slow to increase in general, And in winter just non existent. A 40km drive would see the gauge still on the bottom until I got to work and it sat idling - then I’d get some temp.

Replaces the DSG temping valve about a year ago (Ali express) Made a huge improvement. But still struggled to get from 80 to 90 unless sitting in traffic or loaded (towing trailer for example)

Had the cambelt and water pump done in January (summer here) and got the main thermostat done same time. Independent garage so probably not OEM parts but I digress.

Everything seemed fine, warmed up to 90

Etc etc. Now we’re getting into winter and cooler temps, I’m back to slow warm up and can actually lose up to 20 degrees temp if on a downhill stretch and on overrun (engine braking). I can somewhat mitigate it by holding the box in 5th to keeps the revs up slightly which helps but it’s not really a long term fix.

Is it possible the DSG has gone bad again? It’s done all of 30,000km.

Not sure where to look - do I send it back to mechanic (And cost) ? Gamble on another DSG valve? Something else? I’m mechanically inclined so don’t mind doing bits and pieces but it’s our primary car so I can’t have it down for extended periods (only reason it went to mechanic for belt etc).

Thanks.

Edited 21 May21 May by BloodWorm

I would try first of all by replacing the DSG stat with a new one of a decent brand.

They're not expensive and it's an easy enough job to do DIY.

AliExpress is great for some things but you never know the quality of what you're getting, especially when it comes to car parts

58 minutes ago, softscoop said:

I would try first of all by replacing the DSG stat with a new one of a decent brand.

They're not expensive and it's an easy enough job to do DIY.

AliExpress is great for some things but you never know the quality of what you're getting, especially when it comes to car parts

TBH that was my gut feeling. I did the last one so no issues swapping it. I figured aliexpress couldn’t go too wrong with something that basic though lol.

Also I noticed that you're in NZ. I know in some hotter countries there are different thermostats fitted that are set to open at a much lower temperature, make sure you've got the right one for your climate.

On 22/05/2026 at 18:28, softscoop said:

Also I noticed that you're in NZ. I know in some hotter countries there are different thermostats fitted that are set to open at a much lower temperature, make sure you've got the right one for your climate.

Actually, that’s something I hadn’t considered. Will look further into that.

Having said that, I think the part number matched. I say ‘think’ cause I’m not entirely sure I didn’t get the PN from internet research 🤣

It’s fine when towing or loaded. Just fluctuating in the colder temps with no load. I’ll do the DSG again and hope for the best.