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Discussion Starter · #1 · (Edited)
Hi All,

So I have a rather interesting problem that cropped up. I'll try and give as much detail as i can:

2012 Touareg TDI 3.0L 90k miles.

EDIT: I realize I left out a glaring issue i have, which is a P2201 NOX Sensor 1st Bank error code existing currently. Which I'm tempted to Delete....but That is also an issue.... Most likely unrelated to the issue below...

A couple days ago, I had a low coolant light come on, no big deal, the level was low enough to trigger it, so i (over)filled the tank and drove off. (Perhaps the issue could be TOO much coolant?!)

The following day, I went to drive and the car acted funny, maybe hesitated a bit, but I noticed quickly while driving that the temp gauge went up to just below the red overheating mark (maybe for a second or two), then came back down to the "actual" normal temp at 190*F. I pulled into a parking lot to look at it, nothing leaking or visually concerning, Having owned many crappy cars in my lifetime, I turned on the heater to hopefully dissipate some of the heat if it was in fact overheating. But there was no heat at all coming from the vents. So we drove home (5 miles) and parked it.

Today, I went out with a laser temp gun and let the car come up to temp and was constantly checking all the hoses. upper radiator hose heated up first, lower hose stayed cold for quite some time, but eventually, from what I could tell, the thermostat opened and the lower hose and the other half of the radiator heated up as well. (external hose temps of about 170*F, I would have to assume the coolant inside was at 190*F)

Still no heat from the heater. I opened up the fender liner to inspect the N82 Coolant Shut Off Valve and checked the temps and felt the hoses, all seemed cold, except what I could assume was the supply hose to the N82 itself, which was still only slightly warm from the residual heat of the main coolant, since it didn't seem to be flowing.

So Problem #1, I think the N82 might not be functioning?

Problem #2. While driving today, I filmed and noticed, fairly consistently, that after a mild/hard acceleration, when I let off the pedal, the water temp gauge would rise to just below overheating and return, within a second or two. and would rise accordingly to how hard I had accelerated. (hard acceleration, higher "temp", milder acceleration, mild rise in "temp")

I'll try and post the videos I records shortly.

Here you can see it right as I'm turning, and then as well, towards the end of the video is a great example of what it is doing. (Ignore the heavy mouthbreathing!)


I did check my battery voltage running (14.7V) and off (12.6V) I did use my OBD2 scanner and tested the battery as well and it indicated "warning", not sure what THAT means, but I haven't visually inspected the battery itself yet.,

Hopefully that explains my weird problems!

Thanks in advance!

I found this video, that seems to align with my problem possibly? As far as how the temp gauge is acting, his gauge was acting similarly. I'm not going to start with soldering the ECU though.... Start Free, Start Small....

 

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Just giving advise on the coolant situation I would say see if the tank is still "overfilled". If so either when the vehicle is cold remove some fluid, or when hot, with the vehicle running remove some fluid. In each case get it to the "MAX" mark and see if the problem goes away. This is a closed pressurized system and maybe with too much fluid it is over pressurized and not allowing fluid to be able to move properly.
 
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Discussion Starter · #4 ·
I will pull some water out, it started acting funny after over filling it, so fingers crossed, it's just a lazy mistake on my part.

I have an older VCDS dongle that I'm considering upgrading to work with the new car (currently have the KII-USB for my '02 GTI, doesn't recognize new vehicles)
 

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Discussion Starter · #6 ·
You have bigger issues.....
Where did the coolant go to? Why did it need to be topped up (aka overfilled) ?

I would like to know as well... :geek: I'll try the easy stuff and maybe get a air purge tool as suggested, if it doesn't hold a vacuum, then yes, I'll have more digging to do.

This car is too fancy for me.
 

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Discussion Starter · #8 · (Edited)
Anything liquid cooled is too fancy for you if you notice that you coolant has vanished and you think you can "address it" by simply filling it back up.

Find the leak... it had to have gone somewhere. Usual leaks are in the valley or at the front of the engine.

I'm draining it all, Air-cooled from now on. :geek:

The only real spot that I noticed was "wet", was on the top of the engine, and with some further looking, I found a hose with no clamp on it, that returns to the expansion tank overflow/return.


White Motor vehicle Light Black Automotive tire



from what I can tell, the water level is at the max level, not overfilled as I thought i had done (that little black dash is what I can only assume is the max level, given the morons at the dealership I bought it from sprayed “detailing” stuff in the entire engine bay.
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Discussion Starter · #9 ·
Drained down the coolant as best i could, used the coolant tool, held vacuum, so in regards to "no leaks" it wasn't leaking, obviously that can be a different story with pressure. Ran the heater and let coolant back into the system. Still no heat, and still a temp gauge issue, which seems to have gotten worse. So i may have introduced more air into the system? I'm not saying I did a good job refilling the system! :ROFLMAO::rolleyes:
 

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I'll assume that you're still doing this blindly without the ability to read various sensors.

If that's the case, try bringing the engine up to operating temp with the coolant bottle open to see if it self bleeds sufficiently. Is your rad fan coming on?
 

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Discussion Starter · #11 ·
Yes, blindly, I just ordered the upgraded VCDS dongle to replace my USB-KII. I will give the opened tank a try. From the obd2 reader I do have, I can see the water temp sensor and it’s reading at 190*F. Radiator fan has not come on at all. Checking the temp across the top of the radiator with a laser temp gun it’s 175*F. It does seem to take a long time for the thermostat to open up.
 

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Your reader doesn't indicate what sensor it's reading off... It sounds like it's reading pre rad..... When you touch the rad outlet hose (or shhot it with your temp gun), is it hot?
 

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Discussion Starter · #13 · (Edited)
Your reader doesn't indicate what sensor it's reading off... It sounds like it's reading pre rad..... When you touch the rad outlet hose (or shhot it with your temp gun), is it hot?
EDIT, radiator fan kicked on at 210*F (both sensors reached this temp) and temps came down to 200*F and stabilized there after the fans were on for a bit from running the engine at 2000rpms for a few minutes. So, no apparent issue of overheating. Still no heat from vents.

looking at this as I type:

ECT 2 seems to be the lower rad hose temp sensor, which is now reading 201*F. Car is fully warmed up now. I’m assuming ECT 1 (189*F) is the upper one underneath the turbo inlet?
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still no heat and checking the temp of the hoses that go to the heater control valve.
 

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Discussion Starter · #15 ·
You’ll have to excuse my dislexic ways. I had written down the sensors backwards, I corrected it in the above post. And yes, ECT 2 is the lower rad hose. Which was the lower temp in the photo above. Also confirmed by disconnecting it as suggested.
 

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Discussion Starter · #17 ·
Can you read oil temp or EGR cooler temp with that tool?
From what I could tell, no.

I did fix a couple issues, it was in fact the heater control valve that was stuck. Perhaps from a combination of the coolant leaking and then when i tried to drain and refill the coolant, since it wasn't opening, it wasn't filling. So, I pulled the fender liner back, gave the control valve a few good taps with a screw driver and it was back to normal! Drove the car around for at least an hour, plenty of hot heat and no weird temp gauge rise and fall. And no overheating issues (and there never was, thankfully) I think it all definitely stemmed from that small hose not having a clamp and allowing coolant to escape.

Now, to solve the P2200, P2201, P2209 NOX Sensor issue....
 

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VCDS would've told you that valve wasn't functioning and would've allowed you to monitor it while you're attempting to cyle it, etc. There's probably even an output test function for it.
 

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The NOx sensors are very pricey... you won't like solving those codes!
 

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Discussion Starter · #20 ·
VCDS would've told you that valve wasn't functioning and would've allowed you to monitor it while you're attempting to cyle it, etc. There's probably even an output test function for it.

I have VCDS. Just not a dongle that reads this car......yet! :p . The new dongle is on it's way! This took all of 15 minutes to do and I got an opportunity to visually inspect the hoses for leaks as well as confirm which style valve is back there, something that VCDS doesn't do. :geek:

Thank you for the help and suggestions. :cool:

I tried soaking and cleaning my pre-cat NOX sensor, so at this point, i'll wait for the new dongle to show up and see what's happening.
 
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