2009 V6 TDI engine does not warm up - Club Touareg Forums
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post #1 of 13 Old 08-13-2018 Thread Starter
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2009 V6 TDI engine does not warm up

Hi all!

I have 2009 V6 TDI Touareg and since last November I've noticed that hardly ever my engine coolant warms up to normal 90c temperature. Year back I had no issues with temperature, once it warmed up to 90c, it stayded there. Few times it has done so, that suddenly coolant temperature has raised to 90c and stayed there but most of the time it is around 60-70c when ambient temperature is around 15c. During winter time, auxilary heater (Webasto) is almost always on.

I had thermostat replaced last January but that did not help. Thermostats are such a simple devices, that they should not get broken easily or malfunction.


For example in the picture below, you can see that oil temperature is 80c and coolant is 60c. We've been driving for almost 2h when I took the picture. In the graph picture, I've logged temperatures from ODB using Torque and you can see that coolant is around 60-70c.



Do you guys have any idea what could be wrong? Is there anything I could check myself?


Best regards,
Jukka
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post #2 of 13 Old 08-13-2018
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VW oem thermostats are known for sticking open when they fail.

At least they don't overheat the engine (fail closed) which is the way 90% of the non OEM thermostats fail.

If changing the thermostat does not fix it, the next thing to check is the real coolant temperature with a known probe. I would suspect that one (or more) of the coolant temperature sensors are defective. The gas engines usually have at least two. Hopefully some TDI guru can give you the number and locations for the sensors on your engine.

PS: You may have already noticed, the temp gauge on the dashboard lies. It is really obvious if you are reading the actual sensor temps from VCDS. On my gas V8, everything from 185-215 results in a gauge stuck dead on the 200 mark, the little lying piece of junk.

I drove around for months with a stuck open thermostat because I believed the reading on the dash. Only when cold weather hit did it become obvious there was a problem. Directly reading actual temps showed me what was really going on.
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post #3 of 13 Old 08-14-2018 Thread Starter
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Thanks for your reply.

I'm just thinking what are the odds that the new VW thermostat would fail immediately after installation (certified VW service did the installation)? Or is there something that could break the thermostat after installation?

I've noticed that oil temp is also falling when engine temp is falling, so that would indicate that sensors are ok. And as you mentioned, I've noticed also that temp gauge shows different temperature compared to digital readings from OBD.

Thermostat is located at quite easy spot, so removing and inspecting it should be rather easy task(?)

Br,
Jukka
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post #4 of 13 Old 08-19-2018
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My V10 showed the same temp when the thermostat was stuck open.

2014 Touareg TDi Executive Package
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post #5 of 13 Old 08-19-2018
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It will most likely be a failed or damaged EGR cooler thermostat allowing some coolant flow to bypass the main thermostat and flow thru the radiator.


Have you had any work done recently that line up with the coolant not getting up to temp?


regards
Drag






Quote:
Originally Posted by jhappone View Post
Hi all!

I have 2009 V6 TDI Touareg and since last November I've noticed that hardly ever my engine coolant warms up to normal 90c temperature. Year back I had no issues with temperature, once it warmed up to 90c, it stayded there. Few times it has done so, that suddenly coolant temperature has raised to 90c and stayed there but most of the time it is around 60-70c when ambient temperature is around 15c. During winter time, auxilary heater (Webasto) is almost always on.

I had thermostat replaced last January but that did not help. Thermostats are such a simple devices, that they should not get broken easily or malfunction.


For example in the picture below, you can see that oil temperature is 80c and coolant is 60c. We've been driving for almost 2h when I took the picture. In the graph picture, I've logged temperatures from ODB using Torque and you can see that coolant is around 60-70c.



Do you guys have any idea what could be wrong? Is there anything I could check myself?


Best regards,
Jukka
dragline1570 is offline  
post #6 of 13 Old 08-19-2018
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Quote:
Originally Posted by dragline1570 View Post
It will most likely be a failed or damaged EGR cooler thermostat allowing some coolant flow to bypass the main thermostat and flow thru the radiator.


Have you had any work done recently that line up with the coolant not getting up to temp?


regards
Drag
Drag. There is a second thermostat on the TDI EGR system?

Found some info on it. It is electrical and it fails.
https://www.a5oc.com/forums/audi-a5-...tat-3-0-a.html

Wow. I have already learned so many things from your posts and I keep learning more. Thanks!
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post #7 of 13 Old 08-19-2018
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Quote:
Originally Posted by nickyt View Post
Drag. There is a second thermostat on the TDI EGR system?

Found some info on it. It is electrical and it fails.
https://www.a5oc.com/forums/audi-a5-...tat-3-0-a.html

Wow. I have already learned so many things from your posts and I keep learning more. Thanks!

nickyt the initial information in the discussion in the link provided is incorrect.
It is not a electrically controlled thermostat just a pain small thermostat.
It is mounted just on the front of the EGR cooler inside a small black plastic tube.


regards
Drag
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post #8 of 13 Old 08-19-2018
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^^Thank you for the clarification Drag. Just learned even more.

To Clarify: The 3.0 TDI has the main thermostat that controls engine cooling. It also has a second thermostat built into the egr system that can also affect the engine cooling.
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post #9 of 13 Old 08-20-2018 Thread Starter
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Hi and thanks for your replies!

Few years back, there was some work done to the egr and air intake, but everything worked fine after that (I can't remember exactly what was done, was expensive though :/ ). No other things were done to cooling system after that.

Is that thermostat easily replaceable or do I need renew the whole EGR? In nickyt's link, they said that it can be easily tested if it fails, do you have any idea how I can do it?

I'll try to see if I can spot the thermostat today.

Br,
Jukka




Quote:
Originally Posted by dragline1570 View Post
It will most likely be a failed or damaged EGR cooler thermostat allowing some coolant flow to bypass the main thermostat and flow thru the radiator.


Have you had any work done recently that line up with the coolant not getting up to temp?


regards
Drag
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post #10 of 13 Old 08-20-2018 Thread Starter
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Hi all!


I investigated the engine a little bit my engine and I found the thermostat near the EGR that Drag pointed out (EGR assembly overview picture). Located in tight spot and not easy to renew (at least for me :/ ) The cooling diagram shows also one thermostat in the EGR line, that is not in my engine (CASA). I believe it is in CATA engines only.


In the cooling diagram picture, I drew the flow of the coolant through the EGR and engine. It makes sense, that if EGR thermostat (25) is broken, it lets the cold coolant go throught the EGR and engine block. I assume that the EGR thermostat is not rated for 87c but something lower temperature? At least the color in the picture is not red hot...


Br,
Jukka
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