Funny name!

Yes the thermostat seems bad. Even in winter after I reach 80C+, it won't dip down below that.

Might as well do the water pump too, I did and found my old one to be a bit loose... Since it's right next to the thermostat it's a no brainer.

 

Replace the defective thermostat. I have seen no documentation that GP***8217;s are associated with defeating DPF regeneration commands. The GP***8217;s do operate in Partial Load Heating.

 

Good trouble shooting. The thermostats have a propensity to soft fail resulting in low engine temps, regen requires engine temp to be at a certain level (65C IIRC), so if your thermostat is failed to the point where temps don't allow regens you have a DPF fault.
I replaced the original thermostat around 70k miles, temps were in the 75 to 78 range rather than the expected 88.

How many miles on your car?

 

Sounds like a failed thermostat to me. I put in a new thermostat about a year ago and immediately saw "normal" operating temperatures in the mid-80s Celsius. The only times I've seen those temperatures drop below 80°C has been descending a mountain (meaning coming down several thousand feet) while coasting in gear (which completely shuts off fuel flow to the engine).

 

Thank you for the feedback, all! I ordered a new thermostat and water pump (while I'm in there), and will see how it all works out. $180 shipped is much nicer than the $6k quote from the dealer, so I'm confident this is worth the experimentation.

Car has 138,000 miles on it -- we've had it since 66,000. It has been a tank, but the emissions gear has just given us fits. Hoping this fix gets us to another couple of years of service before we start looking at a newer model.

I will report back with an update after I get things swapped out and some monitored driving hours in!

Thanks again.

 

If you havent been actively regenerating, there is likely to be some soot buildup fallout. pay close attention to your exhaust pressure sensor readings.
There is also a 2nd coolant thermostat that mounts to the transmission heat exchanger. Change this at the same time esp at that mileage!!!

 

Thanks for the tip. I have been seeing a CEL related to exhaust backpressure. Logged some values driving around town. Not sure what the acceptable ranges are... does the "fallout" you're referring to manifest as exhaust blockage or sensor failure or other?

Values from a short drive (while "warm") including coolant temp:

 

That coolant temperature is BAAD! Should be, must be, >80°C.

 

Agree with Doug. Replace that thermostat.

Edit. Went back through the thread and that’s been consensus. When is new thermostat going in?

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Dup. Sorry.

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Thermostat came today, took about 3hrs to replace. The EGR heat exchanger must have been removed previously, because the turbo side came out with no problem at all. Got everything put back together and coolant filled (will top off in the morning when cold), and drove around for an hour or so with the logger on. Operating temperatures are back to normal range, and the DPF regen cycles appear to be working organically -- I didn't request anything or clear any codes.

Coolant temp / Soot mass logs:

I'm still getting backpressure sensor codes. Here are the backpressure logs... any ideas?

Thanks again for the support! Very happy to have avoided the dealership throwing parts at the problem.

 

That's more like it for the coolant temperatures. DPF regenerations stop happening if the coolant temperature does not rise above the minimum for at least 5 minutes (and the min is 75°C if I recall correctly). If regenerations do not occur, that leads ultimately to DPF failure. It is a good sign that you are seeing regenerations now.

 

Regeneration is 60c. Below 75c, glow plug controller activates plugs to help with efficiency and lower NOx.

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Nice success story!