Keep DEF full to the cap - Recommendation from Freightliner/Sprinter Service Manager

I thought I would pass along a recommendation my Sprinter Service Manager shared with me. He said he's now recommending to his customers to keep the DEF tank full to the cap. He said the DEF crystallization issues in partially filled tanks are causing problems particularly as the vehicles get older. While he acknowledges that a constantly refilled tank could eventually have issues from mixing old and new DEF ....he said that's only a warning light that can easily resolved with siphoning and refilling.

He says he's seen a lot of issues this summer caused by crystallized DEF in partially filled tanks that could have been avoided if the DEF tanks stayed completely full. He said this is particurally true of RV based Sprinters that might be driven less frequently than other Sprinters.

It's just an opinion that I thought I would share. Makes a lot of sense to me ....and I intend to follow through with his suggestion

I buy that. I'll need a PhD chemist to explain why mixing "old and new" DEF is an issue. Don't we mix 'old an new' gas, diesel?

What the service Dude didn't mention was keeping the fill port, cap and surround SPOTLESSLY clean of 'white creep' and crystals. Same with a previously opened DEF bottle. It has to be surgically clean, IMHO.

Should I say - I told you so ?

As I become an older Sprinter RVer, I encounter a lot of younger and newer folks who seem to think along the lines "infrequent use, low mileage and long periods of storage are good for health and longevity".
Common sense information like the original post provides are something that could go in thread "Just for Newbies".
Others I would suggest would be "Battery Management/Parasitic Drain", "Run Generator under 50%+ Load Monthly", "Buy a Good Tire Gauge and Use it Often", "Check the Water in Your House Batteries Frequently".
Admitted some of this is droll to those with experience but it would be a godsend to many we meet on the road and in campgrounds.

Thanks for the tip on DEF crystals ...is there anything you use to clean them? Like club soda on battery terminals. I am new to the Sprinter life and enjoy the feedback from all of you experienced forum posters.

What I did most recently accumulating a few crystals at the DEF filler was when I got home from my trip, I used a small screwdriver to break up the crystals and then attacked them with my Shop-Vac. No muss, no fuss, and no worry that I was causing corrosive DEF to flow over the automotive parts below the DEF filler.

Worked well for me. (Of course, at the time of filling the DEF, I poured water over the places where DEF dripped while filling--like the top of my grille and the bumper. Seems almost impossible to keep those 2.5 gallons containers with the chintzy flexible spouts from leaking where you screw the spout onto the jug!)

Rock Doc

PJD said:

Thanks for the tip on DEF crystals ...is there anything you use to clean them? Like club soda on battery terminals. I am new to the Sprinter life and enjoy the feedback from all of you experienced forum posters.

Click to expand...

Wouldn't use anything but water....


I've just taken a paper towel and made a stopper to keep crap from getting in the neck of the DEF bottle. Then, just bottled drinking water (AQUAFINA ...but being a Benz I suppose you could use EVIAN!!!!). Aquafina as we've got a lot of minerals in the tap water. Old tooth brush to scrub. Rinse well.

I'm freeky paranoid about getting anything other than DEF fluid in the tank......

4wheels said:

Should I say - I told you so ?

Click to expand...

Everyone switch to topping off weekly or better yet daily..........6 months or year from now, we are likey to see the same number of failures with the DEF from the sample group. Till then I would delay any celebrations or told you so's.

Tried the 2 1/2 gallon jug of DEF just recently, hard to not make a mess of it, what with the weight of the jug and cheap fill hose. Did this soon after the DEF light came on and it wouldn't take the entire 2 1/2 gallons. Next time will use the 1 gallon jugs and a funnel. Noticed the Wal Mart brand didn't have the ISO number on it so paid a little more for the one with the correct number on it.

When I experience problems I'll let you know. All I've ever done is fill within a couple hundred miles of the DEF warning. 37146 miles in three years and four months.

Old Crows said:

Wouldn't use anything but water....


I've just taken a paper towel and made a stopper to keep crap from getting in the neck of the DEF bottle. Then, just bottled drinking water (AQUAFINA ...but being a Benz I suppose you could use EVIAN!!!!). Aquafina as we've got a lot of minerals in the tap water. Old tooth brush to scrub. Rinse well.

I'm freeky paranoid about getting anything other than DEF fluid in the tank......

Click to expand...

Achtung! Aquafina is tap H2O thus has less minerals(due to filtering) while Evian; ArrowHead; Fiji, etc- at the source pure spring H20 has much more natural minerals!

As for your previous comments regarding adding fresh DEF atop "old" in tank DEF. Why should it matter!, it's DEF marrying DEF!? Yes, old DEF can often form a sheen layer of crystals atop the surface of the older DEF due to heat; evaporating, etc., adding fresh DEF on top does not always totally dissolve the precipitated sheen layer thus it can somewhat remain crystalized and affect the flow.

Yes, it is definitely best to keep your DEF tank topped off!

cheers...

105,000 miles in the 2014 OM-651.
When the low DEF warning note shows, I look for the nearest Tractor Supply Co. store.
Go in, buy a 2.5 gallon kit of TerraCair Ultra Pure DEF, carefully screw on the flex hose to the
top of the container (all plastic, no cardboard box) refill the DEF and I'm good to go for another
5,000 + miles.
http://www.corefluids.com/TerraCair/TerraCair-techsheet.pdf
Did it exactly the same way on my 2010/2011/2012 NCV3's with the OM-642 V6 an never had a
problem.
Just had a CEL Light show up, having to do with the DEF system I believe, so the dealer will have
something to look at in my 120,000 mile service.
Roger

Welcome to another exciting thread of "As the DEF Turns."

Bobficious suggests purchasing a couple of half gallon bottles (see picture) of DEF from the stealership. Yes, I know it's expensive, 13 bucks for half a gallon but if you're a cheapskate worried about spending money you shouldn't of purchased a wallet flushing Mercedes-Benz.

The bottles have a nifty spring-loaded spout that screws into your vehicles DEF tank and dispenses when you push down on the bottle and automatically stops when the DEF tank is full. No fuss no mess! It's so easy a caveman can do it and hopefully you too! It's almost idiot proof!

If I do manage to spill some, I immediately rinse the spillage with tap water making certain of course that the DEF tank is capped during the rinse cycle to ensure that I do not contaminate the contents of the DEF tank. Duh!

Surgically clean is not necessary because were not worried about germs! or are we? (I know, " "Surgical clean" was a metaphor)

For the parsimonious crowd, such as myself, I refill the nifty bottles from LESS expensive 2-1/2 gallon jugs of DEF I purchased from AutoZone.

For the Gucci crowd, take your beast to the dealer and make them fill it for free.

Now, I don't know why all the controversy about keeping the DEF constantly topped off? How much effort does that require? Why let it trigger some stupid Chinese manufactured sensor that may not reset because of some software glitch or defective component?

Now, I am not a chemical engineer but I would assume crystal formation is the result of a reaction with air? If my assumption is correct then it would be prudent to keep the tank full and free of air as much as possible which would lessen the likelihood of crystals forming inside the tank. No?

As for storing a vehicle. The emphasis on design was for operation not storage. Take the vehicle up for a flog at least once every couple weeks! Among other things, this will help reduce the likelihood of tire killing flat spots from forming on the tires.

Hasta la vista amigos!

Bobficious.

Bobnoxious said:

Welcome to another exciting thread of "As the DEF Turns."

Bobficious suggests purchasing a couple of half gallon bottles (see picture) of DEF from the stealership. Yes, I know it's expensive, 13 bucks for half a gallon but if you're a cheapskate worried about spending money you shouldn't of purchased a wallet flushing Mercedes-Benz.

The bottles have a nifty spring-loaded spout that screws into your vehicles DEF tank and dispenses when you push down on the bottle and automatically stops when the DEF tank is full. No fuss no mess! It's so easy a caveman can do it and hopefully you too! It's almost idiot proof!

If I do manage to spill some, I immediately rinse the spillage with tap water making certain of course that the DEF tank is capped during the rinse cycle to ensure that I do not contaminate the contents of the DEF tank. Duh!

Surgically clean is not necessary because were not worried about germs! or are we?

For the parsimonious crowd, such as myself, I refill the nifty bottles from LESS expensive 2-1/2 gallon jugs of DEF I purchased from AutoZone.

For the Gucci crowd, take your beast to the dealer and make them fill it for free.

Now, I don't know why all the controversy about keeping the DEF constantly topped off? How much effort does that require? Why let it trigger some stupid Chinese manufactured sensor that may not reset because of some software glitch or defective sensor.

Now, I am not a chemical engineer but I would assume crystal formation is the result of a reaction with air? If my assumption is correct then it would be prudent to keep the tank full and free of air as much as possible which would lessen the likelihood of crystals forming inside the tank. No?

Ask for storing a vehicle. The emphasis on design was for operation not storage. Take the vehicle up for a flog at least once every couple weeks! Among other things, this will help reduce the likelihood of tire killing flat spots from forming on the tires.

Hasta la vista amigos!

Bobficious.

Click to expand...

From a retired chemist here....Yes, your assumption is correct :


cheers...

I have the large tank underneath on the passenger side. I've always filled till a little runs out. Last time after a little came out the top I kept nursing a little more in and it took another almost 2 gal. I assume this extra space is for expansion when it freezes. I have 175,000 miles with no def problems so it must not hurt to leave that extra space at the top of the tank.

An anecdotal experience with any mechanical device does not prove or disprove that the user habits have any bearing on the out come ....good or bad. ( skipping past abuse or no maintenance)

Failures are statistical random events nothing more nothing less. In the case emissions devices the stats are not in the users favor many times. If you have not had a failure you maybe one or more of the lucky ones. Manufactures track failure rates, warranty parts use etc there is an exact number that can be attached to each system. A great design and perfect parts might have a failure rate in the tenths of 1%. Higher failure rates like 1-10-20% alarm bells go off and updates might happen. By the way most Auto manufactures start counter measures at .5% rates, single digits are crisis mode, double digit failure rates parts are on back order and vehicles are down. DEF Has had multiple software updates and multiple parts improvements.

DEF Is the HOT topic lately .........but.........it was not all that long ago failure of the EGR and all its components or air charge hoses was topic of the day. Today we have all become accustomed to the EGR system and its possible short comings. Back then EGR was customer driving, oil, fuel related and few other theories. Reality is the EGR has a nasty job in nasty environment. Air charge hoses wear out, dry out, split and crack........so it maybe your turn to experience the failure or you may choose to do preventive maintenance????? Or carry a spare hose.
"Y" cable is another example......4-5 parts changes or improvements over several years.

Will say it again........there is a really really good reason VW "forgot" to add DEF to those new vehicles for years on end. Then there is the Japanese that refused to get in the DEF diesel market......DEF was a BIG part of that decesion.

Mein Sprinter said:

Yes, it is definitely best to keep your DEF tank topped off!

cheers...

Click to expand...

OK, so when or how often does one top off? Daily, every fuel fill, once a week, once every two weeks, once a month? How about within 500 miles after the DEF warning?

I try to replenish the DEF within 100 miles of getting the low DEF warning.
Never had a problem with any part of the SCR systems in any of my Sprinters.
I try to replenish with TerraCair Ultra Pure DEF 2.5 gallon kits from Tractor Supply Co.
Roger

jackfish said:

OK, so when or how often does one top off? Daily, every fuel fill, once a week, once every two weeks, once a month? How about within 500 miles after the DEF warning?

Click to expand...

That's up to you, whatever conscience tells you. But scientifically speaking it's best to top it off now and then.

In the case of Sailquick, he runs his Sprinter daily and accumulates thousands of miles where his DEF keeps "moving" while ours tend to sit thus might crystalize sooner due to air being introduced.

Absolutely agree with this statement, "Will say it again........there is a really really good reason VW "forgot" to add DEF to those new vehicles for years on end. Then there is the Japanese that refused to get in the DEF diesel market......DEF was a BIG part of that decision." by Showkey.

cheers...

It would seem that topping off prior to any longer term storage session would be a given. That is unless there is some official MB recommendation to do otherwise.

Keep in mind that many of these problems/topics can become more complex/obsessive than necessary the more they are hashed over.

The idling of a diesel Sprinter during normal use discussions come to mind.

vic