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-   -   Urea question (http://www.jeepgarage.org/f222/urea-question-67461.html)

nautiboy 11-02-2013 03:05 PM

Urea question
 
Just had an interesting conversation with my neighbor. He had been looking at buying the new Jeep CRD but ended up getting the Mercedes ML because his wife couldn't sit in the Jeep seats.

Anyway ... he hasn't received his ML yet, but he was talking to the dealer about things he should know about since it was his first diesel, and that's when he learned about the urea tank. And apparently Mercedes charges $350 to fill the urea. :eek:

When questioned why it was so much, they said that first of all it's $32/gal for the fluid and the tank is a little over 7 gallons. And the rest is because they "flush" the urea tank for you. When questioned further, it turns out it's not a flush (which I would think is not even really possible), but they siphon out any remaining urea before adding more.

They apparently explained to him that urea crystalizes as it gets older so you need to make sure you get all the old urea out first. Further, they said that because of this crystallization, you absolutely should not top up urea tank periodically and instead should wait until you're almost out, drain the remainder and then fill it up.

I hadn't heard anything like this before, and it sounded like a bit of FUD to encourage them to pay the dealer $350 to do it. Obviously the $32/gal is "Mercedes markup" - you can get it much cheaper elsewhere. But what about the notion of not topping up periodically and/or having to drain the urea tank to avoid old urea?

Any thoughts/info on this?

bill_de 11-02-2013 03:55 PM

Re: Urea question
 
The Jeep manual says "top it off"

" EngineWillNotRestartinXXXXmiDEFLowRefill Soon–ThismessagewilldisplaywhenDEFdriving rangeislessthan500miles,DEFfluid top off is required withinthedisplayedmileage.Themessage willbedisplayedintheEVICduringvehiclestartup withthecurrentallowedmileageandaccompaniedby asinglechime.Theremainingmileagecanbepulled upanytimebywayofthe“Messages”listwithinthe EVIC"


My tablet drops spaces when copying from PDFs

Baalic 11-02-2013 03:59 PM

Re: Urea question
 
the urea will crystalize and its nasty too. So some truth to that, also if you accidently put it in your diesel, your motor is now trashed.

food for thought

CNY_WK2 11-02-2013 04:42 PM

Re: Urea question
 
Quote:

Originally Posted by bill_de (Post 922765)
The Jeep manual says "top it off"

" Engine Will Not Restart in XXXX mi DEF Low Refill Soon–This message will display when DEF driving range is less than 500 miles,DEF fluid top off is required with in the displayed mileage. The message will be displayed in the EVIC during vehicle startup with the current allowed mileage and accompanied by a single chime. The remaining mileage can be pulled up anytime by way of the“Messages” list within the EVIC"


My tablet drops spaces when copying from PDFs

Fixed

mtnmerlin 11-02-2013 06:32 PM

Re: Urea question
 
Quote:

Originally Posted by nautiboy (Post 922737)
And apparently Mercedes charges $350 to fill the urea. :eek:

When questioned why it was so much, they said that first of all it's $32/gal for the fluid and the tank is a little over 7 gallons. And the rest is because they "flush" the urea tank for you. When questioned further, it turns out it's not a flush (which I would think is not even really possible), but they siphon out any remaining urea before adding more.

They apparently explained to him that urea crystalizes as it gets older so you need to make sure you get all the old urea out first. Further, they said that because of this crystallization, you absolutely should not top up urea tank periodically and instead should wait until you're almost out, drain the remainder and then fill it up.

I hadn't heard anything like this before, and it sounded like a bit of FUD to encourage them to pay the dealer $350 to do it. Obviously the $32/gal is "Mercedes markup" - you can get it much cheaper elsewhere. But what about the notion of not topping up periodically and/or having to drain the urea tank to avoid old urea?

Any thoughts/info on this?

My CRD is about three weeks behind yours on the delivery schedule. Your question prompted me to research this.

It looks like the answer depends on temperature and DEF age. If you are using DEF (driving enough) for it to not get too old and do not have hot temperatures, then there is no problem. The DEF evaporates into ammonia at elevated temperatures. Shelf life is 23 months at 86 degrees F; 10 months at 95 degrees F; 4 months at 104 degrees F. Thus, not driving much in a hot climate may require occasional draining. Otherwise, draining is not needed (according to my research).

DEF crystallizes when it freezes or dehydrates (evaporates). Thawing or re-hydrating (adding new DEF) dissolves the crystals. DEF begins to freeze at 10 degrees F, so the tank and DEF lines are heated at cold temperatures to prevent freezing.

Mike V 11-03-2013 12:51 PM

Re: Urea question
 
Quote:

Originally Posted by mtnmerlin (Post 922842)
My CRD is about three weeks behind yours on the delivery schedule. Your question prompted me to research this.

It looks like the answer depends on temperature and DEF age. If you are using DEF (driving enough) for it to not get too old and do not have hot temperatures, then there is no problem. The DEF evaporates into ammonia at elevated temperatures. Shelf life is 23 months at 86 degrees F; 10 months at 95 degrees F; 4 months at 104 degrees F. Thus, not driving much in a hot climate may require occasional draining. Otherwise, draining is not needed (according to my research).

DEF crystallizes when it freezes or dehydrates (evaporates). Thawing or re-hydrating (adding new DEF) dissolves the crystals. DEF begins to freeze at 10 degrees F, so the tank and DEF lines are heated at cold temperatures to prevent freezing.

So in 110 degree F you would be better off halve filling to keep the crystallization to a minimum unless your were driving a lot. I wonder if its easy to remove the line to flush the tank? I'll see when mine gets here and report back. I get at least 6 weeks every summer of 115+ days. I will flush it after a few weeks of heat and see what kind of build up I get. I may also let some crystalize and see if it disolves when submerged in new DEF.

Mike V

mtnmerlin 11-03-2013 01:34 PM

Re: Urea question
 
Quote:

Originally Posted by Mike V (Post 923163)
So in 110 degree F you would be better off halve filling to keep the crystallization to a minimum unless your were driving a lot. I wonder if its easy to remove the line to flush the tank? I'll see when mine gets here and report back. I get at least 6 weeks every summer of 115+ days. I will flush it after a few weeks of heat and see what kind of build up I get. I may also let some crystalize and see if it disolves when submerged in new DEF.

At 122 degrees F, the shelf life is 1 month. It looks like a 2 month shelf life around 113. I will probably be in southern Arizona a lot in summers.
My garage typically sits at 92 degrees. I suppose I will keep the DEF bottle in the air conditioned house or in a refrigerator.

I was thinking along the same lines as you. Something like: keep the tank low in the summer and add occasionally. It might be good to know how to drain the tank, huh? I wonder what they do in the land of Oz? I bet 45 degrees C is kinda normal in the interior.

Mike V 11-03-2013 01:53 PM

Re: Urea question
 
I don't think the exports have the urea injection system. Thats why those units were shipped and not sitting in storage...

Mike V

colby1035 11-03-2013 06:59 PM

Re: Urea question
 
I own a 2011 BMW 335d, Straight 6, twinw turbo diesel engine. Also takes the same DEF(Diesel Exhaust Fluid)/Urea.
While DEF does have a certain shelf life, its not like you need to worry much about it.
If you drive your car much it will use the DEF and it will not crystallize. The DEF tank is sealed so there is no evaporation. Now if the car sits for an extended period of time there may be some crystallization with the urea in the lines, and nozzles running to the exhaust.

As far as flushing the DEF tank. When the 335d first went on sale in 2009 BMW would flush the DEF tank before a refill. They later switched to just topping off the DEF a year or 2 later. This was with the BMW 4 year maintenance program on new cars. SO was it just a way to save money, or was it really not needed? Who knows.

Last thing on DEF price. You can get 2.5 gallon at Walmart for $13. It is also much easier to fill on the jeep compared to my BMW. All you need is a funnel.
I need a special tool to open the cap, then a special nozzle to pour into the tank, and it takes a long time relative to what one would think.

So moral of this post. Buy the DEF and a $3 funnel from walmart. Pour Def into the tank when you get a "1000 mile to empty" warning, or whatever warning the jeeps get. DEF fills should be similar miles to an oil change.
Buy Fresh DEF and fill with fresh DEF. Don't let it sit in your garage for over 6 months, then try and use it.

Mike V 11-03-2013 07:26 PM

Re: Urea question
 
Thanks for the info from an experienced oil burner!:D

Mike V

shoestring 11-03-2013 07:47 PM

Re: Urea question
 
Yeah, there's definitely no reason to pay a dealership such obscene DEF prices when it can easily be obtained elsewhere for a few bucks per gallon.

Here's some good info on DEF from Cummins for all of us diesel auto newbies:

http://www.cumminsfiltration.com/pdf...es/MB10033.pdf

BobT 11-04-2013 02:05 AM

Re: Urea question
 
Quote:

Originally Posted by mtnmerlin (Post 923179)
At 122 degrees F, the shelf life is 1 month. It looks like a 2 month shelf life around 113. I will probably be in southern Arizona a lot in summers.
My garage typically sits at 92 degrees. I suppose I will keep the DEF bottle in the air conditioned house or in a refrigerator.

I was thinking along the same lines as you. Something like: keep the tank low in the summer and add occasionally. It might be good to know how to drain the tank, huh? I wonder what they do in the land of Oz? I bet 45 degrees C is kinda normal in the interior.

As you know, we don't require urea in Aussie Grands however there are trucks that do require it. Down here it sold as AdBlue. The only reference I can find to crystallization is in relation to drying of spillage and seepage. When dry, it leaves a residue of crystals that can be corrosive to paintwork. It is readily soluble in water so easily removed. AdBlue is a 32.5% concentration of pure urea in demineralised water so it's mostly water anyway. I can't see how there could be crystallization in the tank unless the tank is allowed to dry out.


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