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Discussion Starter · #1 ·
Hi, so we bought a '16 Touareg TDI Exec a bit over a year ago, and we absolutely love the thing. We bought it for the reason of towing, and this year we finally bought our travel trailer. its 21ft long, unloaded the trailer weights about 4300, hitch Is 480, and FULLY loaded its 5760, I would say we are rocking about 4500-4600 with stuff/food in it. Honestly tows it really well, don't feel like there is an issue (minus MURDERING MPG 30ish to about 12ish and DEF :) )
However, my question is this----I have noticed that when I go uphills it starts to get a lil hot, normally runs at 200deg, going up a hill, will go to 205, top the hill, back down to 200...next hill, 210, back down to 200....longer type bigger hill its gotten to 235, once I top the hill, drops fairly quickly to 200 again. I have noticed if I shift it manually I can try to control it a bit and it doesn't get as bad, but almost any hill its doing this.

I read a few other forums and someone said to clean the radiator with a hose and water get the gunk outta there, didn't help, made sure I had enough coolant, topped it off..no difference.
Anyone have this issue? or any ideas what could be causing it? the first time it happened I even got an "add oil" and I got SUPER worried, but, after adding in 1qt its been fine, levels are good. My garage is SUPER DUPER clean and I workout on it every day so I would notice if ANYTHING was leaking.

it has NEVER hit the red area, and once I top the hill, RIGHT back down....im concerned a bit, espeically since I am going to be towing the trailer from New Mexico to LA, Cali in July, and thats crossing Needles, Cali, which is like 115+ degrees in the summer. Also, I never had issues without the trailer, or in traffic or anything, only uphills.
 

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Discussion Starter · #3 ·
Mine is a V8, but exhibited the exact symptoms as yours. Was a failing water pump. Something to consider.
I DO NOT like your answer! NNNNEEEEXXXTTTTTTT!
jk...that is good info to have. cuz it does almost seem like the therm is stuck and then it "opens" cuz it does drop down VERY quickly!
 

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You're cooling load increases significantly uphill when towing while youre air flow will be reduced if you're also slowing down. I'm not saying the cooling system shouldn't keep up but I think dessert temps and flat roads do not present the same demand.

Def have it checked and you might also try an AC coil cleaner on the radiator. It deals with surface clutter that you can't necessarily see but does impact cooling efficiency. We use it on the house AC's routinely
 

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Discussion Starter · #5 ·
ya I did clean the radiator, didn't use any fluids to clean it but I did use my pressure washer and tried to spray as MUCH as I could outta it to clean it. think I should throw it on there and then do it again? I didn't remove the bumper or anything, I just got in there as much as I could through the grill. I should also note that I just hit 60K on it, so its not like it has a ton of miles either.
your comment about dessert temps and flat roads do not present the same demand, I live in a dessert, but also have fairly large hills as well.

I did set it up with a German auto repair shop to check the coolant system pressure and the fans and such checked to make sure they are pushing enough air as well.---its the first step I can think of to check....but I am open to ideas as well.
 

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If you can stop when the temperature at its highest, don't switch the engine off but open the hood to see if the coolant fan is running or if it cuts in.
 

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I'd take an IR gun to the radiator when its up to temp and look for temp differences. Your radiator may not be circulating as it should.
 

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Apologies if it seems to be a hijack but not intended that way.

While my water temp stays at 90C (194F) my oil temperature reaches 138C (280F) when towing up hill. Ambient 35C (95F). Is this normal? What is the max?
 

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What speed are you trying to run uphill? I tow a 5k lb boat and 4 people throughout Arizona; just came back from a trip to Catalina towing on the i10 through Blythe/Indio with an even 100 degree temp. Uphill, I’ll set the cruise to 65mph, and as the temp gauge rises, I’ll bleed off speed to 55mph. The temp gauge sits at 220 until I crest the hill and quickly cools down to 200F. Even at 55, I’m passing other trucks with trailers but I’m in no rush. I leave it in D, which will run 5/6 gear depending on the incline, and on the flats 7/8 not shifting frequently. Overall, I think the Touareg TDI does a great job given that it’s not a dedicated tow truck. I’ve towed in 110+ degree weather on i40, i17, and the future i11, same result every time, cruising 55-65 on the inclines. On the flats it’ll hold 80mph easily. I go through about 2.5gal of DEF every 3k miles when towing, and average around 12mpg with inclines, 14-16mpg on flat roads.
 

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Discussion Starter · #12 ·
I think it’s relevant because I am wondering if the turbo is heating up during uphill towing spitting the hot oil into the oil pan and heating it up, too the hill turbo cools and so does oil?
do these things have an oil cooler? It does have some sort of heat exchange in front of the radiator but it is tiny.
 

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Discussion Starter · #13 ·
What speed are you trying to run uphill? I tow a 5k lb boat and 4 people throughout Arizona; just came back from a trip to Catalina towing on the i10 through Blythe/Indio with an even 100 degree temp. Uphill, I’ll set the cruise to 65mph, and as the temp gauge rises, I’ll bleed off speed to 55mph. The temp gauge sits at 220 until I crest the hill and quickly cools down to 200F. Even at 55, I’m passing other trucks with trailers but I’m in no rush. I leave it in D, which will run 5/6 gear depending on the incline, and on the flats 7/8 not shifting frequently. Overall, I think the Touareg TDI does a great job given that it’s not a dedicated tow truck. I’ve towed in 110+ degree weather on i40, i17, and the future i11, same result every time, cruising 55-65 on the inclines. On the flats it’ll hold 80mph easily. I go through about 2.5gal of DEF every 3k miles when towing, and average around 12mpg with inclines, 14-16mpg on flat roads.
So sounds fairly similar, however I haven’t hit 100+ degrees yet, been into the 90s but not 100 yet.
So i typically run cruise on 70mph cuz I noticed MPG is HIGHLY impacted at 75. Up hill, depending on the hill ill either stay at 70, or big hills i have dropped down to as low as 55. But, like you said it’ll go up, then RIGHT back down. However I have gotten it to 235 or so before. That was in about 85degree temps.

I tend to pull around 12-14mpg on a typical tow, but we dont have like anything flat. I have seen as low as 9mpg. For DEF, i am NOT getting 3K or anywhere near that! 3-4K miles I’ve gone through about 10gal or so IF i had to guess, I’m starting to track it cuz it seems excessive—-but multiple people have said tow with a 2.5gal DEF container
 

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I think it’s relevant because I am wondering if the turbo is heating up during uphill towing spitting the hot oil into the oil pan and heating it up, too the hill turbo cools and so does oil?
do these things have an oil cooler? It does have some sort of heat exchange in front of the radiator but it is tiny.
Yes, they have oil cooler and transmission cooler.

Has the cooling system ever been taken apart?
Sometimes there is a vapour lock causing erratic cooling temp
 

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Discussion Starter · #15 ·
No it has never been taken apart. I’ve owned it for about a year never had a problem just started towing this is my 5th time towing 2nd time it’s happened so I’m JUST diving into it
 

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Seems weird that it would heat up that much then cool down to normal rate. Possibly a stuck thermostat?
Have you ever tried to put the interior heating up to max when the temp does go up? It will take away some of the heat? This might give you a better indication whats happening in the cooling circuit. I have never had any cooling problems and never heard of any one else having these sorts of problems. Just seems odd.
Usually if the circuit has been opened at some point, it pays to bleed it properly or it can give you erratic readings.
Someone has mentioned taking a laser thermometer and see if the readings are consistent across the radiator when the Treg is hot and the thermostat has opened. A Treg that is 5 years old should not have any blockages in the radiator unless water was the only thing used and not proper coolant.
Another thing to consider is that the gauges is not reading correctly??
 

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Discussion Starter · #17 ·
to be honest it does act like a stuck term, but what are the chances that it gets stuck on every hill, and happens to open at the top of every hill? also, it doesn't happen AT ALL not towing either.
 

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Hi, so we bought a '16 Touareg TDI Exec a bit over a year ago, and we absolutely love the thing. We bought it for the reason of towing, and this year we finally bought our travel trailer. its 21ft long, unloaded the trailer weights about 4300, hitch Is 480, and FULLY loaded its 5760, I would say we are rocking about 4500-4600 with stuff/food in it. Honestly tows it really well, don't feel like there is an issue (minus MURDERING MPG 30ish to about 12ish and DEF :) )
However, my question is this----I have noticed that when I go uphills it starts to get a lil hot, normally runs at 200deg, going up a hill, will go to 205, top the hill, back down to 200...next hill, 210, back down to 200....longer type bigger hill its gotten to 235, once I top the hill, drops fairly quickly to 200 again. I have noticed if I shift it manually I can try to control it a bit and it doesn't get as bad, but almost any hill its doing this.

I read a few other forums and someone said to clean the radiator with a hose and water get the gunk outta there, didn't help, made sure I had enough coolant, topped it off..no difference.
Anyone have this issue? or any ideas what could be causing it? the first time it happened I even got an "add oil" and I got SUPER worried, but, after adding in 1qt its been fine, levels are good. My garage is SUPER DUPER clean and I workout on it every day so I would notice if ANYTHING was leaking.

it has NEVER hit the red area, and once I top the hill, RIGHT back down....im concerned a bit, espeically since I am going to be towing the trailer from New Mexico to LA, Cali in July, and thats crossing Needles, Cali, which is like 115+ degrees in the summer. Also, I never had issues without the trailer, or in traffic or anything, only uphills.
What altitude and length of hill are you climbing? Climbing a steep hill for extended mileage can be held on any car and I know California has lots of those

What system are you using to monitor coolant and oil temperature?

Do you have the purple g14 coolant, the only type of coolant that should ever be in a Volkswagen or Audi, or are you using some other ****?

You are using the proper rated oil and synthetic for the car right?
 

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The tstat may not be stuck but perhaps it doesn't fully open. That wouldn't be noticeable under typical conditions whereas towing it hill it could have an impact. Again, the IR gun...pull,over when it's hot and check various hoses etc and get some actual temps.
 

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I don’t think it’s a stuck thermostat nor anything wrong with your car. Although the Treg can tow 7700lbs, we’re pushing a lot of power, fuel, and heat through a 3.0L V6. The turbo is going to heat up, EGTs will too and at some point when it gets too high the computer will dial back the power. Yes, the car has an oil heat exchanger via coolant. We’re towing the same weight in the same conditions, but the difference is I’m towing a boat which is more aerodynamic.

The coolant gauge is not linear. When it sits at normal 200F, it +/- 20F. Once it crosses that variance, it will then drastically move to the next tick where it becomes more linear. The owner’s manual states this is normal under load and it’s ok to operate the vehicle with elevated temperature until it hits the red zone (260F).

In my opinion, the TDI tows great but we are experiencing the limitation of having a smaller engine demanding a big load sustained. We are pushing a lot of fuel through a 3L engine. Dedicated tow trucks, like a RAM 2500 have a 6.7L 6 cylinder or semi trucks have 13L 6 cylinder diesel. It’s ok that the temp gauge will rise, it just indicates that the engine is working harder to run 70mph uphill in 100F with a 5000lb trailer that sticks out is maybe asking too much. If it hits the red, it definitely is. In my case, I’ll bleed off the speed to 55mph where it sits at 220F which I’m comfortable with. I love my Treg TDI, it has good fuel efficiency, handles great, and tows what I need.
 
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