engine coolant temp

[grohgreg]

This 2011 TDI Sport is my 9th diesel. Every one I've owned previously had thermostats between 70C and 85C (160F-185F). Yet this Touareg wants to run at an indicated 210F (instrument panel gauge). Can it possibly have a 100C thermostat, or is this something I should have checked out? No check engine lights/faults/codes by the way.

I asked a VW service manager, he was evasive and unwilling to look it up. His solution was for me to bring in the car. Not sure, but I'd guess the lack of response is profit-driven - in that they don't get paid unless they write up a work order.

//greg//

[Keithuk]

Well I don't have any spec for the 2011 Touareg2 TDI but a Golf (03-08) 1,9D TDI PD is 85°C.

When your tempersature gauge shows 210°F thats 99.6°C the normal position is straight up on a Golf and that 190°F in the US or 90°C in Europe. So if yours is showing 210°F all the time then I would think its running hotter than it should, get it checked out? (failed water pump already )

An engine runs most efficient the closer to 100°C it can but as we know water boils at 100°C thats why cooling systems are pressurised. For every 1psi increased the boiling temperature increases by around 1.5°C.

Now just because the thermostat opening temperature is 85°C there will be some part of the engine that are running alot higher than that so thats why it maintains an average engine temperature.

[grohgreg]

Originally Posted by Keithuk

An engine runs most efficient the closer to 100°C it can but as we know water boils at 100°C thats why cooling systems are pressurised. For every 1psi increased the boiling temperature increases by around 1.5°C.

What you say may hold true for petrol engines, but I've been around diesels for a long long time. As stated, my previous 8 diesels (3 Euro, 5 Asian) employed thermostats ranging from 70C to 85C (158F to 185F), the majority used 80C (176F). Pressure caps are rated higher for petrol engines as well. My previous diesels typically ran 7 psi caps, one even had a 4 psi cap

With what little info than I've been able to obtain thus far, this Touareg seems to be the odd man out. Even moreso, since it doesn't even appear to have a pressure cap on the expansion tank. Instead, there's threaded plastic cap. Another oddity is the coolant color. Book says it should be purple. Mine's unquestionably pink.

I'm hoping for real-world input from other US-spec 2011 Touareg TDI owners. Because from what I've seen since owning this vehicle, they seem to know more about their cars than do the VW service reps (in my area).

//greg//

[chittychittybangbang]

That threaded plastic cap should be the pressure cap. There is no radiator cap.

G12, G12+, and G12++ are pink and purple. Diluted with distilled water they are pinkish, very light purple. They are interchangeable.

[grohgreg]

Originally Posted by chittychittybangbang

There is no radiator cap.

I understand that. It's why I specified "on the expansion tank". But surprisingly, it's NOT a pressure cap. It's just a threaded blue chunk of plastic with no apparent capability to vent. Of my previous 8 diesels, several had a pressure cap on the expansion tank, some on the radiator itself. But not one of them DIDN'T have a pressure cap - somewhere. .

That said, can you contribute to the actual question here? That is, what's my coolant thermostat temperature supposed to be? Once I determine the correct OEM thermostat temp, I'll be able to conclude whether or not the temp gauge is telling me the truth.

//greg//

[Keithuk]

Originally Posted by grohgreg

What you say may hold true for petrol engines, but I've been around diesels for a long long time.

Even moreso, since it doesn't even appear to have a pressure cap on the expansion tank. Instead, there's threaded plastic cap.

That statement applies to petrol and diesel.

Pressure cap pressures can vary the same as thermostat temperatures, the Touareg pressure cap is 1.4bar - 20.3psi. There are 2 types of expansion (reservior) bottle shown for the Touareg a round one and an oblong one depending on engine number.

The threaded plastic cap is the pressure cap is in the expansion tank.

They also do two different engines for your Touareg 3.0D and 4.2D both TDI but you don't state which is yours?

[grohgreg]

Originally Posted by Keithuk

That statement applies to petrol and diesel.

Pressure cap pressures can vary the same as thermostat temperatures, the Touareg pressure cap is 1.4bar - 20.3psi. There are 2 types of expansion (reservior) bottle shown for the Touareg a round one and an oblong one depending on engine number.

The threaded plastic cap is the pressure cap is in the expansion tank.

They also do two different engines for your Touareg 3.0D and 4.2D both TDI but you don't state which is yours?

Your responses suggest that US and UK 2011 Touaregs aren't set up quite the same. That's why I mentioned that other owners of the US-spec 2011 Touareg TDI Sport may have the answer I'm looking for.

But to address your points;
(1) the only 2011 Touareg TDI engine in the US is the 3.0 liter V6 inter-cooled turbo-diesel. The 2011 petrol model is a 3.2 liter non-aspirated V6, the 2011 hybrid has an Audi 3.0 super-charged petrol V6. Those are the only engines available here. And I'm only concerned with the diesel.
(2) My own long term diesel experience still supports an argument against your assertion that petrol and diesel engines run optimally at the same temp. As stated, my 8 previous diesels had thermostats with much lower opening temperatures (1@70C, 1@72C, 5@80C, 1@85C). Two of them by the way were Mercedes, one a Citroen. This Touareg however appears to be running at 100C. Therein lies my question.
(3) And my expansion tank is oblong, but has no apparent means to vent over-pressure. The installed cap is just that, a blue plastic threaded and unvented cap that has two raised icons; one indicating "check owner's manual", the other "careful - it's hot".

//greg//

[wensteph]

The manual calls for normal operating temp to be straight up and down, center of the gauge. On US models that's 200F. Mine runs with the left side of the needle at the right side of the 200F mark.

My coolant is also pink. manual says one of the additives is purple, maybe when diluted it's pink.

To me it sounds like your car is running normally.

[grohgreg]

I put my Innova 3140 on the question, and it shows the coolant rising and falling in the 194-201F window. While the constant rise and fall of the coolant temp was reflected by the 3140, the temp gauge i the dash didn't move a molecule. That tells me two things;
(a) I've got a 195F thermostat, and
(b) the VW temperature gauge is little more than an idiot light with a needle.

I think it's fair to conclude that the idiot gauge needle only reflects temperature variances something in excess of the 7 degree swing reported by the 3140. If I can figure out how to link the 3140 with my PC and make a graph out of that live data, maybe I can come up with a more definitive explanation. But for now I'm satisfied that the engine temp is fine, it's just the gauge that sucks.

//greg//

[TDV6]

The dash temperature gauge is a hot/cold indicator, as far as I am concerned. Not only is the indicated temperature often incorrect, but the response time is so damped that it does not show short term temperature cycles at all - towing up a long grade for instance. I run a Scangage II on my TDI Touareg all the time, my normal operating temperature is 93C (199F), but when towing up a long grade 103C (217F) is not unusual. The dash temperature gauge never moves. The Scangage should be accurate as that is the temperature reported to the ECU. These temperatures are normal, and nothing to be worried about.

Your 210F on the gauge could well be lower in reality - check it with VAGCOM.