2015 GSW not coming up to temperature

mvoss15

Well-known member
Joined
Jul 31, 2005
Location
Indiana
TDI
2014 Audi Q7 TDI, 2015 Golf Sportwagen TDI (previous 05 Jetta TDI, 09 JSW TDI, 05 Jeep Liberty CRD)
I have a 2015 GSW TDI, 107,000K miles. For the past several weeks, I've noticed I haven't been reaching full temperature on the dashboard gauge - it's been one tick left of center. Suspecting a possible thermostat issue, but, nothing else seemed to be the matter. We got some really cold weather here this week, and the gauge now has been 2-3 ticks left of center even after 20-30 minutes of freeway driving. Clearly not normal, and seems like i'm not getting normal heat output in the car too. Ran a scan in VCDS, and nothing obvious shows up (happy to post the results if helpful).

Failing thermostat? I'm having a hard time finding any sort of instruction on thermostat replacement - looking at a picture of the part, it seems like a pretty major job. I assume this would NOT be covered under the TDI emissions warranty? Any help or thoughts appreciated!
 

mvoss15

Well-known member
Joined
Jul 31, 2005
Location
Indiana
TDI
2014 Audi Q7 TDI, 2015 Golf Sportwagen TDI (previous 05 Jetta TDI, 09 JSW TDI, 05 Jeep Liberty CRD)
I'll take a look next time I go out. Not sure I've noticed an oil temp option in the MFD.
 

mvoss15

Well-known member
Joined
Jul 31, 2005
Location
Indiana
TDI
2014 Audi Q7 TDI, 2015 Golf Sportwagen TDI (previous 05 Jetta TDI, 09 JSW TDI, 05 Jeep Liberty CRD)
Just checked, I do not have an oil temperature option in the MFD. I don’t see any way to turn that on through the settings either. Is this something I can enable with VCDS?
 

nathanso

Veteran Member
Joined
Mar 31, 2019
Location
Redwood City, CA
TDI
2015 GSW TDI S 6M
My 2015 GSW TDI S has this display option and it didn't require any fiddling with VCDS. It takes some horizontal and vertical scrolling through the various displays using the steering wheel buttons to find it, but it should be there (it's in the Driving Data group that contains range to empty, mpg since start, and current mpg). My car's oil temp typically runs 200-220F once the car is up to operating temperature.



 
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DivineChaos

Top Post Dawg
Joined
Jul 27, 2019
Location
Minnesota
TDI
mk6 jetta sportwagen tdi
Do these throw a code if the thermostat is failing? With it being cold, it's sadly normal for our tdis to run a bit colder. Have you blocked off your rad grill
If it was your thermostat you'd have heat when parked, but when your moving you wouldn't.
 

mvoss15

Well-known member
Joined
Jul 31, 2005
Location
Indiana
TDI
2014 Audi Q7 TDI, 2015 Golf Sportwagen TDI (previous 05 Jetta TDI, 09 JSW TDI, 05 Jeep Liberty CRD)
I've been through all the options in the MFD - no oil temp. I'll check it with VCDS after a long drive later today. Mine's a 2015 TDI SEL - not sure if that made any difference?

And I've had the car through plenty of winters where we've been sub-zero temperatures - and not had any issues. But now it's not coming to temp even in 32 degree weather. I'll pay closer attention to if it changes when I idle for a while.
 

RIP TDI

Top Post Dawg
Joined
Feb 16, 2000
Location
Santa Barbara, CA
TDI
'15 GSW SE 6MT, '01 Golf GLS 5MT, '96 Passat variant
The oil temp readout is a distraction from your issue, but to get it to display in the MFD display options menu, I believe the coding change required is: Instruments-17 > long coding > byte 10 > activate bit 1.

Now for your actual problem, there are a couple of areas to investigate. VW coolant temp gauges are typically "smoothed" right around the normal temp range, i.e. a good bit of temperature variation in this normal operating range is NOT indicated on the gauge; it instead remains rock steady at 12 o'clock. When you check actual operating temp with VCDS, don't be surprised if it is actually LESS than your visual interpretation of the gauge reading. But your check of actual temps may point to a lazy gauge sensor or gauge itself (after removing the smoothing phenomenon from the equation). As for the cause, I think you've already hit on the most likely explanation: a lazy/failing thermostat. This engine also uses a variable output primary water pump, which is theoretically capable of sticking in the "full flow" position and which would slow the speed of coolant warmup, but only at temps lower than full operating, so I think this would be an extremely remote possible cause of your issue. Perhaps if this were combined with a lazy thermostat, it might contribute slightly to the problem.
 

adjat84th

Veteran Member
Joined
Dec 13, 2008
Location
Virginia Beach, VA
TDI
'01 Jetta TDI/'15 Golf TDI
At 101k miles, I installed a new engine with brand new thermostat and there is a very noticeably shortened time for the coolant temp gauge to reach NOT. Oil still takes its sweet time, but I'm thinking my thermostat on the old motor was getting pretty lazy. These are not fun to change btw. Core support in the service position, remove charge pipe, "throttle" valve and its coolant lines, and also the support bolted to it and the block.

Your description of not noticing in previous winters only points more to it slowly dying. You could block the front and live with it for a while longer, or just replace it.
 

mvoss15

Well-known member
Joined
Jul 31, 2005
Location
Indiana
TDI
2014 Audi Q7 TDI, 2015 Golf Sportwagen TDI (previous 05 Jetta TDI, 09 JSW TDI, 05 Jeep Liberty CRD)
Well - still havent been able to diagnose it further, but, yesterday noticed a small puddle on the floor of the garage, and immediately got a "check coolant" warning when starting the car. Sure enough - coolant was low, and there's coolant puddled on top of the plastic belly pan looking down into the engine compartment. Probably need to take it in...wondering if any would be covered by extended TDI warranty?
 

DivineChaos

Top Post Dawg
Joined
Jul 27, 2019
Location
Minnesota
TDI
mk6 jetta sportwagen tdi
Well - still havent been able to diagnose it further, but, yesterday noticed a small puddle on the floor of the garage, and immediately got a "check coolant" warning when starting the car. Sure enough - coolant was low, and there's coolant puddled on top of the plastic belly pan looking down into the engine compartment. Probably need to take it in...wondering if any would be covered by extended TDI warranty?
Unless it's the EGR cooler . Probably not.
 

mvoss15

Well-known member
Joined
Jul 31, 2005
Location
Indiana
TDI
2014 Audi Q7 TDI, 2015 Golf Sportwagen TDI (previous 05 Jetta TDI, 09 JSW TDI, 05 Jeep Liberty CRD)
Ended up being a leaking water pump - assuming something with the variable water pump was also causing the temperature issues. Forced me into doing the timing belt a little early (at least by miles) but all seems to be back to normal now.
 

reactor

Member
Joined
Mar 26, 2021
Location
spokane
TDI
mk7 sportwagen
One of the worst thermostat locations, probably can do timing belt with water pump replaced quicker lol
 
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