[platydog55]

Hi Clubers,
Hope someone can advise on my coolant temperature problem.

Bought a 2010 V6 TDI in April interstate, and driving home saw that the coolant temp (and oil temp, which ~equals coolant temp at all times) rarely went to 90 deg C where it should, when it did it was only for a short while, it was mostly 70 or less sometimes 60 deg.

So, thermostat was changed, the full VW OEM part which is thermostat and cover complete. Result was not much change, except it has not yet made it to 90, it stabilises at 65-70 deg C, but with odd ups and downs of 5-10 deg while driving in normal traffic, flat road. So maybe the coolant temp sensor is bad. Have confirmed the dash temps being shown are real using a thermometer –it is indeed running cold.

Changed the coolant thermostat (on bottom radiator hose) and again, no change.

My next step in the “change it till it’s fixed” approach is the oil temp sensor, with the thought that something about the software controlling the tempreature set point integrates the readings from both sensors and so with one incorrect the ste point is wrong? .

But before I do, has anyone experience with this type of temperature issue? All previous cars in my lifetime have run flat and stable temps at the right level when a good coolant temp sensor and thermostat are in place. Maybe there is a calibration procedures for 'resetting' the desired teperature too?

Also no codes on my scanner relevant to cooling issues.

And maybe a related question – how long till I should see the temp starting to rise from cold? All other cars I’ve owned it took a km or so, this Touareg usually takes 7Km (to the low levels I mentioned above (which would be a thermostat issue normally, except it’s been replaced.. ).

Cheers,

David

 

[platydog55]

Hi again Clubers,
This post got caught in the spam/modeeration queue and (as a new user) I am not sure it has been seen recently - so this is my attempt to bring it forward again
David

 

[seafarer28]

Hi David,


You are right, the Touareg temp should stabilise around the 90 degree mark, pretty much in line with the oil temp, also in my experience with 2 x 7L's it does take 6-8kms to reach thoat temp but once there, is should not change under normal driving conditions.
You seem to have an oddity if the temps fluctuates in traffic or stop start traffic, mine sits at the 90 mark pretty much irrespective of driving situations and has only increased when towing on a long uphill stretch, never goes below the 90 even in an Australian summer with 100 degree temps.
I do know that the gauge does not show the actual coolant temps (when checked agains VCDS) as it tends only to start showing temp increases after it reaches some unknown parameter, yours seems to show temps lower than 90 which is a bit of a puzzle, first time I've heard of that happening.
To be honest, I wouldn't play aroungd with the oil tem sensor as it seems there is nothing wrong with it.
as a final thought, if you can get access to a VCDS you can check the actual coolant temp against what the gausge is showing in real time.


TonyB

 

[platydog55]

Thanks Tony.

I'm leaning toawrds the VW OEM thernostat replacement being defective despite it being a new part, it makes the best sense to me unless there is an electronic control system issue I am not aware of.

I did not test it in a suacepan before fitting to see that it opened OK as water approached boiling (but why should I, it's a perfect VW part ) - and though not keen to pull it out to do it, to get it replaced I would need to know that it's a bad one for certain as well.

Is there a listing of Adelaide / Australian non-VW VCDS locations, or is this just a matter of calling around for a suitable garage wth the gear?

Cheers

David

 

[Built4Sin]

Platy, you could boil the previous thermostat you pulled and see what temperature its opening at. Just to verify it had actually failed, thus possibly clearing that system.

 

[platydog55]

Platy, you could boil the previous thermostat you pulled and see what temperature its opening at. Just to verify it had actually failed, thus possibly clearing that system.

Built4Sin , a point I forgot to mention. I did boil it and it never even opened.

Which is certainly defective, but the opposite effect would have occurred, I should have had overheating, not under heating problems.

Along with the erratic (but aloways) low readings on 2000 km trip (and in ordinary traffic), I had to think that I might had an intermittent / variable failure of the thermoststat with the old thermostat, but with the new one doing someting similar it's still really a mystery to me.

Cheers
David

 

[nickyt]

I had to fix a bad thermostat in the past. The things I learned was...

The electronic gauge on the instrument panel lies. You will have to have something else to go by. VW deliberately wrote programming to make this happen. Grrrr...

It is therefore impossible to diagnose the problem with the gauges. I used a VCDS. There are other options, but you will need something diagnostic.

I don't know about your engine, but I have two coolant sensors that monitor the engine coolant temp at two different locations.

My thermostat is behind the freaking timing belt. There is no way I am NOT going to test that puppy with boiling water and a thermometer. It got tested on open temp and close temp TWICE!

It is best to get something similiar to ecstuning.com/b-schwaben-parts/coolant-refill-air-purge-tool. I love how easy that thing makes the coolant fill.

 

[platydog55]

I had to fix a bad thermostat in the past. The things I learned was...

The electronic gauge on the instrument panel lies. You will have to have something else to go by. VW deliberately wrote programming to make this happen. Grrrr...

It is therefore impossible to diagnose the problem with the gauges. I used a VCDS. There are other options, but you will need something diagnostic.

I don't know about your engine, but I have two coolant sensors that monitor the engine coolant temp at two different locations.

My thermostat is behind the freaking timing belt. There is no way I am NOT going to test that puppy with boiling water and a thermometer. It got tested on open temp and close temp TWICE!

It is best to get something similiar to ecstuning.com/b-schwaben-parts/coolant-refill-air-purge-tool. I love how easy that thing makes the coolant fill.

Thanks nickyt,
My 2010 V6 has the thermostat readily acessible behind only the serpentine belt, so fairly easy once you remove the belt. Is your thought that I may have air caught in the system to cause all this? I have no water-gurgling noises when starting/running (I had a Subaru Liberty that did ).
But thanks for the info on the gauges being useless, how helpful of VW...
David

 

[nickyt]

It is possible that it is just air in the system. We don't know for sure yet. I can tell you that modern cars are now being designed with the idea that the coolant will be vacuum filled. So, there are engines on the market that will never "burp" and remove air.

A water pump failure usually moves less water, so that normally makes an overheat situation.

I have one last thing you can check on. Since I don't have a TDI, I don't try to keep up on them but I remember something about some of the TDI engines used a water cooled EGR system. It was possible on some engines for this system to never close and it would delay the engine coming up to operating temperature.

Found it. Thanks again to dragline1570 for sharing his knowledge!

clubtouareg.com/forums/f93/2009-v6-tdi-engine-does-not-warm-up

.

 

[Built4Sin]

Built4Sin , a point I forgot to mention. I did boil it and it never even opened.

Which is certainly defective, but the opposite effect would have occurred, I should have had overheating, not under heating problems.

Along with the erratic (but aloways) low readings on 2000 km trip (and in ordinary traffic), I had to think that I might had an intermittent / variable failure of the thermoststat with the old thermostat, but with the new one doing someting similar it's still really a mystery to me.

Cheers
David

Hmm, I thought the thermostats fail full open, which is why you would have under heating issues, like you have now. Could be vapor lock, like what Nickyt is posting, but I think that ends up leading to an overheating situation, with water not flowing correctly. The EGRs do have a thermostat, of which mine is getting replaced (newer TDI engine though, so not exactly related).



Here are some awesome diagrams and clickable part links. I'll post the breakouts below.

Feed: https://volkswagen.7zap.com/en/rdw/touareg/toua/2010-616/1/121-121061/
Return: https://volkswagen.7zap.com/en/rdw/touareg/toua/2010-616/1/121-121062/

 

[nickyt]

Thermostats can fail full open, full closed, or stuck in between. Open seems to be more common.

My current best guess is that an egr system malfunction is causing the under heat.

clubtouareg.com/forums/f93/2009-v6-tdi-engine-does-not-warm-up