Elevated Coolant Temp

Just purchased a used 2013 Passat TDI 6M down in California with ~145k miles. I was down in SoCal, saw the car for sale, bought it and drove it back to the Seattle area.

On the return drive, I noticed that the coolant temp gauge would elevate past the mid-point (190F) when driving up a significant grade at freeway speeds for extended periods. It maybe went a notch above...nowhere close to the red. Still, I wouldn't expect this to be normal/ideal. I just purchased a ScanGuage II and will be monitoring the temp. So far on city driving it gets to about 210F. My understanding is that the thermostat should be 189F and understand there will be fluctuation.

At what point does it become concerning and should it be addressed? It could be a number of things and can get expensive trying to sort out the issue. I have read through some posts and understand the heater core issues that people have been having. Thinking about a flushing out the system first and seeing if that'll help.

Also if there is DPF/EGR delete, would that help in terms of the heater core issue that seems to be plaguing these cars? From what I've read, it seems when the DPF activates it heats things up considerably which can cause the coolant "get nasty" and clog things up. I could have misunderstood the issue and would love any insight here.

Thanks in advance!

Hi Gleater,

I have a 2013 6M Passat TDI and I have noticed the same issue and had the same concern. I have been monitoring it via my Polar FIS and noticed that the needle doesn’t move off 190 until the coolant temp hits 226 in the FIS. I’ve never seen the coolant temp go higher than 231. I start babying it when I see the needle move. I currently have 65k miles and have been witnessing this since about 40k I think. Maybe just hadn’t noticed it before that or put enough load on it.

I’d love anyone else’s experience with this too.

-Matt


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Post fix I have noticed higher temps 215-220F via scangauge during normal driving.

jjblbi said:

Post fix I have noticed higher temps 215-220F via scangauge during normal driving.

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That's interesting. Both Matt and I don't have a fix for ours since we have manual transmission (2012-2014). Only 2015 had a fix for the 6-speed manuals.

Yeah we don’t have a “fix”, but we did have a recall that, at least in CA, was required to register the vehicle and I don’t remember where I read it, but it definitely included a flash that altered emissions behavior (increased DEF consumption) and thus affected fuel economy and probably cooling system behavior too. The thermostat isn’t electronically controlled but the intercooler pump is and so are the fans.


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matteo2u said:

Yeah we don’t have a “fix”, but we did have a recall that, at least in CA, was required to register the vehicle and I don’t remember where I read it, but it definitely included a flash that altered emissions behavior (increased DEF consumption) and thus affected fuel economy and probably cooling system behavior too. The thermostat isn’t electronically controlled but the intercooler pump is and so are the fans.


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Interesting. I'm sure my car got that "fix" as it is a CA car. Thanks for that info. Another in the "+" column for DPF and EGR delete.

Indeed. I would delete mine in a heartbeat if I could get away with it in Riverside county.

One thing I have been doing that I recommend until you can fully delete is just disable high pressure EGR. All you have to do is disconnect the valve wiring harness (just before the intake manifold). It may be all in my head, but I believe I got a slight mileage bump out of it. The real plus with doing this is keeping the soot from clogging your intake track and causing long term problems. Monitoring the soot level with the Polar FIS with and without it connected shows a typical DPF soot load reduction of about 80%.

I don’t know of a way to quick and easy disconnect the low pressure circuit, but that’s filtered so it’s less of an issue. You can disconnect the flapper valve in the exhaust midpipe which creates pressure to force re-breathing of low pressure EGR. I felt an improvement in the butt-dyno when I did that one.

The one downside in disconnecting those two is having to live with a check engine light. Luckily for you, once you order your Malone delete tune, they can turn off the CEL for those specific codes.

Hope this helps!
Matt


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EGR will def help keep things nice and toasty, so anything you can do to disable it will help keep things cooler. If you can delete it's def for the best.

740GLE said:

EGR will def help keep things nice and toasty, so anything you can do to disable it will help keep things cooler. If you can delete it's def for the best.

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Thanks for the reply...and that is the plan now.