Periodic Van Use - DEF Fluid Drain?

Hexnut

New member
I have a 2016 Sunseeker MBS 2400R on a 2015 MB chassis that of course uses DEF. Since I live in a hot climate and use the MH only occasionally, the DEF may degrade sooner than in other conditions. Is anyone aware of a way to drain or pump the DEF so the tank can be filled with fresh fluid?
 

Cheyenne

UK 2004 T1N 313CDi
Re: DEF Fluid Drain?

But, unless you thoroughly rinse the DEF tank after draining the old DEF then what is left MAY crystallise on the sensors and lead to problems.

I personally would have thought it better to top off the DEF before putting your RV into storage so the sensors remain 'wet'.

Others may disagree, just my opinion...

Keith.
 

Old Crows

Calypso 2014 View Profile
Re: DEF Fluid Drain?

Like my Gramps would say: "If she ain't broke..... DON'T FIX IT!"

Can high temps degrade DEF. Yes. However, it really hasn't been a big fat problem. There's no data to support DEF degradation due to high ambient temps in the field. The warning is in the DEF literature and MOST LIKELY applies to virgin bottled DEF in storage & NOT in use. (I don't see how anyone could even measure DEF degradation in street use. WAY too many variables to count. And WAY too many data points to collect and try to make any rational sense out of the data.)

Just keep adding DEF fluid periodically (maybe ever other or every 3rd or 4th fuel up).
 
D

Deleted member 50714

Guest
Re: DEF Fluid Drain?

But, unless you thoroughly rinse the DEF tank after draining the old DEF then what is left MAY crystallise on the sensors and lead to problems.

I personally would have thought it better to top off the DEF before putting your RV into storage so the sensors remain 'wet'.

Others may disagree, just my opinion...

Keith.

I don't think crystals will form in a closed container? I base this on observations of my half-filled half-gallon containers.

Definitely top off DPF prior to long-term storage. Same for fuel.



Like my Gramps would say: "If she ain't broke..... DON'T FIX IT!"

Can high temps degrade DEF. Yes. However, it really hasn't been a big fat problem. There's no data to support DEF degradation due to high ambient temps in the field. The warning is in the DEF literature and MOST LIKELY applies to virgin bottled DEF in storage & NOT in use. (I don't see how anyone could even measure DEF degradation in street use. WAY too many variables to count. And WAY too many data points to collect and try to make any rational sense out of the data.)

Just keep adding DEF fluid periodically (maybe ever other or every 3rd or 4th fuel up).
I was curious too if it can sour.

I say top her off and go for a nice hour highway pleasure drive.
 
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irvingj

2015 RT SS Agile (3.0L)
I do what Cheyenne does... any time I know it's going to sit for a while, I top it off. And Bob, yes, that's a "sealed container," BUT.... it does have a vent to atmospheric pressure.. so it's not really sealed...:professor:
 

sailquik

Well-known member
The engine compartment (the DEF reservoir is usually in the engine compartment on later Sprinters) is certainly a lot cooler
ambient temperature on a parked/stored cold soaked Sprinter than it is on a Sprinter that is up to normal operating temp.
Perhaps the DEF degradation/crystallization is significantly less on a parked/stored Sprinter when compared to one that
that is operating a full operating temperatures.
It would seem that Cheyenne's "keep the components "wet" by filling the DEF reservoir BEFORE storing the Sprinter
is probably the best overall option.
If you are going to store it for > than 2 years (the normal shelf life of DEF fluid per AUS 32/ISO 22241-1 and -2 DEF standards) it could be
a good idea to pump out the expired DEF and the refill it with fresh DEF before putting the vehicle back into service.
pfflyer's suggestion to purchase a DEF refractometer and test the purity of your DEF fluid is an excellent idea.
Roger
P.S. Here's a little video on using a DEF Refractometer to test your DEF concentration:
https://www.youtube.com/watch?v=cNvT1esgc40
 
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pfflyer

Well-known member
Re: DEF Fluid Drain?

Like my Gramps would say: "If she ain't broke..... DON'T FIX IT!"

Can high temps degrade DEF. Yes. However, it really hasn't been a big fat problem. There's no data to support DEF degradation due to high ambient temps in the field. The warning is in the DEF literature and MOST LIKELY applies to virgin bottled DEF in storage & NOT in use. (I don't see how anyone could even measure DEF degradation in street use. WAY too many variables to count. And WAY too many data points to collect and try to make any rational sense out of the data.)

Just keep adding DEF fluid periodically (maybe ever other or every 3rd or 4th fuel up).
They do make DEF fluid testers. I believe it measures the urea’s purity or concentration.

https://www.amazon.com/gp/product/B01DVAL4I2/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
I got one to test a 5 gallon pail I bought on clearance from Tractor Supply and for future tank tests in the RV. I could not find a date code on the pail and I wanted some sort of assurance a deal was actually a deal before I used it.
 

TooMuchHair

Active member
Hexnut, you are correct to be concerned. Take a look at this chart. https://goo.gl/images/tHNzG5
I do agree with the idea of keeping the tank full during storage. If it isn't "too" hot during long storage periods then pumping out the old to test or replace with fresh DEF when ready to drive the van again would be a good plan. But consider the possibility that if the storage temp is "too" hot, the DEF might degrade to the point that it might need changed even earlier....?
I also recommend cleaning the DEF injection nozzle periodically. I cleaned mine at about 12K miles, all highway, no idle time and it was close to being plugged.
 

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