Coolant Temperature Drop - Sharan 7N

Today, I noticed that when the vehicle was rolling downhill, the coolant temperature dropped by two notches. Before that, the gauge was at 90°C.

This is a 2015 CFGC model with 33,000 kilometers on the odometer. With my previous 7N model equipped with a CFGB engine, I never observed this behavior.

This leads me to two questions:

Is it certain that the coolant thermostat is 100% defective?
2. What options do I have for locating potential defects?

Probably just by logging the temperatures and occasionally feeling the radiator with your hands during the warm-up phase.


If I remember correctly, the Sharan has a rather complicated thermostat that someone incredibly cleverly installed. It's located somewhere behind the oil filter, air intake manifold, and other components.

I also suspected something similar with my cfgc, but after investigating the installation location, I found it to be fine.

matthiasTDI96 wrote:

I also suspected that with my cfgc, but after examining the installation location, I found it to be fine…

I've only had the car since April, so I don't have any winter driving experience yet. I can only compare it to the older CFGB model. There's still a significant difference, though: the CFGC has dual-clutch transmission (DSG), while the CFGB was a manual transmission.

These funny, modern cars...

I think I should get a Land Cruiser with a 4.2L diesel engine. They are often sold even with 500,000 kilometers on the odometer.

A TPI (Temperature Profile Indicator) might show that the coolant temperature drops again at low load in winter conditions, even though everything is functioning correctly. And that's how it should be, given the mileage.
I once had a similar issue with a Passat 2.0 TDI CR. I replaced the thermostat, which is a fairly involved process, but it still didn't work. As far as I can remember, the problem was with the DSG transmission cooler thermostat, which is integrated into a water hose and needs to be replaced entirely.

Hello...

"Do all three of your boxes do the same? It's probably normal in the winter. If you have a standing heater, you could turn it on to see if it helps."

The Passat, even with the DSG (dual-clutch transmission), suffers from this issue. The DSG completely disengages (sailing), and in neutral, it can't produce enough heat. Moreover, the DSG is cooled via the coolant.


SG
Manfred.

Thank you. Your answers reassure me for now. I have a urea tank (AdBlue tank) and use it regularly. However, I can't imagine that with an outside temperature of 0°C and almost no load, the oil temperature and coolant temperature would already be dropping to the point where the exhaust aftertreatment system can still function correctly.

vag-driver wrote:

... that the exhaust gas cleaning system can still function in compliance with regulations.

That was good...!

Check out the thermostat for the DSG transmission. They tend to fail and get stuck in the open position.
z.B. 1K0 121 113 A

We're back from vacation now. After approximately 2500 km, I could no longer observe the temperature dropping. In other words, once the water temperature reached 90°C, the gauge stopped moving.

Therefore, I am currently ruling out a defect.