Def Temp high

[me262]

On my last trip I first used a new bluefire to monitor my def parameters. The def temp seems to be increasing and not leveling off. On my 7 hour trip I started out with the def temp at 70f and ended up with the def temp at 104f but the outside air temp at the destination was 82f with most of the 7 hour trip was in the 70's.

On my return 7 hour trip the def temp started out at 86f but the coach sat outside the day before with the outside air temp reaching 98f. The starting outside air temp was 70f. When I returned the def temp was 109f with an outside air temp of 88.8f. Most of this trip was driven in an outside air temp in the middle 70’s with the last 2 hours in the middle 80’s.

I so far haven't had any fault codes show up and I feel if I make another trip greater than 7 hours the def temp fault code will be shown. My question is at what temp should the def temp level out at? At what max def temp will a def temp fault code be thrown? I have a gen 6 def head with about 5000 mi.

[Ljwt330]

Originally Posted by me262

On my last trip I first used a new bluefire to monitor my def parameters. The def temp seems to be increasing and not leveling off. On my 7 hour trip I started out with the def temp at 70f and ended up with the def temp at 104f but the outside air temp at the destination was 82f with most of the 7 hour trip was in the 70's.

On my return 7 hour trip the def temp started out at 86f but the coach sat outside the day before with the outside air temp reaching 98f. The starting outside air temp was 70f. When I returned the def temp was 109f with an outside air temp of 88.8f. Most of this trip was driven in an outside air temp in the middle 70’s with the last 2 hours in the middle 80’s.

I so far haven't had any fault codes show up and I feel if I make another trip greater than 7 hours the def temp fault code will be shown. My question is at what temp should the def temp level out at? At what max def temp will a def temp fault code be thrown? I have a gen 6 def head with about 5000 mi.

I cannot answer your questions about the max temps, but what you report is consistent with others who are concerned about where the DEF reservoir is located and it's proximity to heat from the engine. Many have insulated the DEF tank from the heat sources for the very reasons you suggest, and the likelihood that high temps influence sensor failures.

[me262]

Originally Posted by Ljwt330

I cannot answer your questions about the max temps, but what you report is consistent with others who are concerned about where the DEF reservoir is located and it's proximity to heat from the engine. Many have insulated the DEF tank from the heat sources for the very reasons you suggest, and the likelihood that high temps influence sensor failures.

I did have a modified heat shield between the muffler and def tank. On mine the muffler is only 6 inches from the def tank but this shield did not stop the rise in def temp.. It seems the def heater is on and not turning off. I would like to know the engineers theory of operation and design used in this Spartan chassis which includes the built in design of def heater.

[USMCRET]

From my reading, you will get a code when the DEF temp hits 120 deg. I’m reasonably certain that info came from a tech at a recent rally.

The heater you are referring to is simply a hose carrying engine coolant that is routed through the DEF head/tank. It is controlled by a valve that is supposed to open only during certain temperatures to prevent the DEF from freezing. I don’t have the actual temp value on the tip of my tongue.

[NCRog]

Originally Posted by me262

I did have a modified heat shield between the muffler and def tank. On mine the muffler is only 6 inches from the def tank but this shield did not stop the rise in def temp.. It seems the def heater is on and not turning off. I would like to know the engineers theory of operation and design used in this Spartan chassis which includes the built in design of def heater.

Exactly my concern. I have my DEF temp continuously visible on my Silverleaf display. I have only checked it on a couple of very short trips, but will get the chance to monitor multi hour use over successive days in another week. On my K3 chassis the tank is sitting in the engine bay, there's no shielding, there's not even anything which remotely lends itself to a thermally shielded compartment. I will take my thermal gun with me to try and get a better assessment of the radiant heat source. Yes, the tank is only inches from the upper treatment muffler, but, based on the temperature of the inner skin of the DEF door, my money would be on the exhaust cross pipe (from the turbo exhaust to the mufflers) as being a major culprit.

[Dutch Star Don]

Our friend with a 2019 Allegro Bus called Tiffin, as he was checking his DEF temps. Tiffin said the DEF won't alarm until 168 degrees. Now that number is on a Tiffin with a Shaw head.

Correction.......Just rechecked my friend's text, he said Cummins doesn't log a fault until 168 degrees.

[Joedoggs]

I have been monitoring my def temp using a digital thermometer…shooting into the top of the tank after removing the blue cap…k3 605 Spartan…..keeping the 15 gallon def tank 80% or more full…outside air temp was in the 80’s and upper 90’s..the cooler day when stopped after running 500 miles the def fluid read 140 degrees..the second hotter day after 500 miles the def was 157 degrees…..this was running down the highway taking it easy…65 mph towing a Jeep…..it’s awfully warm back there with the exhaust,after treatment chamber,engine etc etc….thx joe b 2019 king aire

[NCRog]

Originally Posted by Joedoggs

I have been monitoring my def temp using a digital thermometer…shooting into the top of the tank after removing the blue cap…k3 605 Spartan…..keeping the 15 gallon def tank 80% or more full…outside air temp was in the 80’s and upper 90’s..the cooler day when stopped after running 500 miles the def fluid read 140 degrees..the second hotter day after 500 miles the def was 157 degrees…..this was running down the highway taking it easy…65 mph towing a Jeep…..it’s awfully warm back there with the exhaust,after treatment chamber,engine etc etc….thx joe b 2019 king aire

Wow! Are you able to verify this temperature by pulling up the DEF TEMP on your King Aire SilverLeaf dash display?

I assume you’re using something like one of those handheld thermal guns to get the fluid temperature in the tank. They’re great for getting temps of solid surfaces but I’ve never had a lot of success to get fluid temps. It’s a fairly wide beam and a narrow tank neck, I would bet the unit is also picking up temps from surrounding areas. But, if your data is correct, the DEF must be deteriorating rapidly at these elevated temps.

I also have the K3 chassis and agree it’s pretty hot back there. My assessment is it’s mainly radiant heat, with the treatment chambers just to the rear of the tank and the cross engine turbo exhaust pipe just above. The inner skin of my DEF door above the latch is almost too hot to touch! However, it’s not as easy as putting up heat shielding, which might impact whatever benefit the whole area gets from being exposed to entrained and radiator fan airflows.

[Joedoggs]

I am not familiar with how to access that info in Silverleaf,haven’t looked for that….but yes I believe these def fluid temperature readings are accurate…based on the temperatures not only of the liquid but of the areas around it…….I think at these temps the def will deteriorate rapidly…I am carrying jugs of bludef stored under the bed,fresh dates and keeping the tank full…I test the urea concentration both in the tank and the jugs before filling the tank…..and had considered using heat shield but became concerned that it was probably trapping heat in as much as keeping heat out….the lower side of the def tank gets lots of air while driving….also,fortunately I haven’t heard of any gen 6 failures yet…but I am taking every precaution that I am aware of…joe b 2019 king aire

[NCRog]

Originally Posted by Joedoggs

I am not familiar with how to access that info in Silverleaf,haven’t looked for that….

On your rear view camera screen you should have some of the SilverLeaf info displayed … mine is 4 lines (one larger than the other 3) plus the TPMS status. I normally have instantaneous mpg, HP, fuel level and DEF level. Using the SilverLeaf knob, scroll down to one of those lines and press the knob, you will be able to scroll through all the parameters on the CANBUS, including DEF temp. Select one by pressing the knob again and that parameter gets displayed on the screen.

I did a short trip last night as an experiment. OAT was in the low 80’s, my SilverLeaf DEF temp read between 82 and 85 (the tank is full). After getting back and shutting down I used the thermal gun in the DEF bay. The door inner wall was at 155, similar to other structure in the area, including the top of the tank. I opened the filler cap and tried to shoot inside, came back at 157, but then I checked the front wall of the tank, half way down, that was only 84 deg … similar to the SilverLeaf readings. I also shot the treatment tank, about 210 deg at its nearest point to the DEF tank, and the exhaust cross pipe, over 300 deg at a similar distance from the DEF tank.

Yes, there’s a lot of heat back there, and a lot of air flow. I used to work with jet engines - thermodynamics and gas dynamics - but I’ve no idea what to shield (or whatever) and whether that would even make things worse. For now I plan to keep the tank full and monitor DEF temp on the dash screen.

[me262]

The question I still have is it normal to have the def temp sensor read 109f after driving around 7 hours in average temps of middle 70’s to middle 80’s? Also, where exactly is the def temp sensor located?

[NCRog]

Originally Posted by me262

The question I still have is it normal to have the def temp sensor read 109f after driving around 7 hours in average temps of middle 70’s to middle 80’s? Also, where exactly is the def temp sensor located?

I'm making a 1,000 mile trip next week, and will monitor DEF temp in real time. Based on my simple and short test yesterday the displayed temp was close to the tank wall temp, below the DEF level, which probably approximates to DEF bulk temp, but I need see how that changes with a few hours of highway operation. Subjectively, a reading of 109 deg F might be high.

The temp is measured in the DEF head and is part of the MSU sensor, see the attached link (post #92) for a better understanding of the head and its components. However, it's tough to understand whether this temp reading is taken before or after the coolant heater stage of the head. Operationally, at this point in the delivery, the system isn't worried if the DEF is further degraded ... the next step is injecting it into the treatment chamber, where warmer is probably better. Does it indicate a malfunction in the coolant valve? No idea, maybe Cummins can hook it up to their tool and see that level of detail.

https://www.irv2.com/forums/f278/lat...-525122-7.html

[NCRog]

It's taken a few days, but I have some results after daily runs of 4 to 6 hours.

Bottom line is, as viewed from my Silverleaf display, the DEF temp just keeps on rising throughout the trip ... at no time did I see it ever come down. Typically each day would start with the temp approximately at ambient temp, then it would increase, tough to give a rate, but after 4 hours with ambient temps in the mid 90s it would be in the 115-120 deg range. It gets worse with idling or heavy traffic, I did see 124 as the highest number ... likely the result of thermal soak-back from all the hot surfaces in the area of the tank.

My new DEF head is a Gen 7, but my data research is being compounded by another issue. With a full tank the quantity readout (confirmed by the DEF quantity lights on the light bar) starts close to 100% but then drifts down to around 58% over the next hour or two. It started right after about an hour running post DEF head replacement, so I think that's the issue. No warnings and no fault codes, but I don't want to disconnect connectors, etc to troubleshoot any further. I have a service appointment at Spartan in a few weeks and we'll let them try to resolve the issue.

Coming back to the DEF temperature. I've done several thermal gun surveys during en-route pit stops, I'm even more convinced the issue is the cross engine exhaust (from the turbo on the driver's side to the treatment tanks on the passenger side), it runs a few inches from the tank and is in the 300-400 deg range even with its braided sleeving. I think the thermal situation will improve if I can find a way to support a panel of hot-rod firewall heat shielding between the pipe and DEF tank. Something like Heatshield Products lava shield, which is adhesive backed.

[Dutch Star Don]

Let's remember that prior to the change in DEF head sensors in 2016, coaches were running DEF without an issue, no matter what the temp was outside. Heck, we took our 2014 DS to Death Valley.

So......if DEF didn't have issues in hot weather before the new sensors, why would it degrade now, just because you can read it's temperature. So even with a sensor that can tell you temps, it needs to reach 168 degrees, that's pretty hot.