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-   -   X35D thermostat, maint and musings (https://xoutpost.com/bmw-sav-forums/x5-e70-forum/109625-x35d-thermostat-maint-musings.html)

FellowsheepTech 01-14-2019 12:35 PM

X35D thermostat, maint and musings
 
So...
I replaced thermostats a couple of weeks ago & twice had a lot of coolant leak overnight out of the quick-disconnect fitting on the front bottom passenger side (the point many have recommended for draining the system). In all the threads I read through, I never saw this mentioned but the fitting seems prone to this? If it happens again I'm replacing the fitting with a flush kit.

Checking temps, it's now operating as expected, but just returned from a 700mi trip & was very surprised/disappointed to have LOST 3-4 MPG (down to 23ish from 27ish). I drive hard, and often go back & forth from NAS Pax area (SOMD) to Binghamton, NY...so some mountains involved (still hard for me to say that having grown up in Colo.). Factors:

1. I'm sure the primary factor is upgrade from std. 18" stock wheels & worn tires to 20" M-sport staggered wheels with nearly-new General Lexani tires. Much wider, but sized for these X5s and typically new tires would give better mileage than old. These came off a 2009 3.0i X5, so I assumed they were correct size/circumference, but just ran them through online calculator & it shows approx 1.3% difference. Is there a way to correct the computer for tire circumference?

2. I've now put 7kmi on the truck, and got a DEF low warning for the first time. I was told it was topped when I bought it, & I've never added, but have noted on scanner that regenerations were happening, though didn't analyze frequency. I would expect better regen with higher engine/coolant temps, but it was regenerating before; I truly have no idea how much DEF I should expect to use? I wish there were a way to read the level!

As an aside, why fill both passive & active sides if the passive feeds the active side?

Now we've got to go fix the aftermarket lights on my son's 540...

ard 01-14-2019 01:00 PM

Don't assume the seller filled the tank... Or even filled both tanks...of filled them properly.

FellowsheepTech 01-14-2019 07:58 PM

Quote:

Originally Posted by ard (Post 1152066)
Don't assume the seller filled the tank... Or even filled both tanks...of filled them properly.



Fair enough. Still curious what “normal” usage is & why fill both if one feeds the other?


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josiahg52 01-14-2019 08:19 PM

I'd have to look at my records but 10k miles even up to 15k miles seems to be my interval for DEF fill ups. I could even tell you how many gallons I've used over that time. I used to fill the passive and active tanks but now just fill the passive tank when it comes time. I'm thinking of even changing that and just fill it every oil change which for me is 7k or so miles. There is method or technique to filling to make sure it's properly filled. Now that I know how much and how often to fill, I know not to stop until I get that much in.

Pretty sure BMW uses all the same speedometer calibrations for wheel and tires sets so I doubt there is a routine method to adjust this. Perhaps with some deep level programming, it could be changed. I doubt they'd have made it easy or straightforward.

FellowsheepTech 01-14-2019 08:42 PM

Thanks, appreciate the feedback


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josiahg52 01-14-2019 10:46 PM

I bought my X5 from a dealer in Maryland with a little over 71k miles on it. I was told that the DEF tanks were filled. A little over 3k miles later I got the warning:
Odometer at Low DEF warning: 74124
Date of Low DEF warning: 12/17/2014
Volume of DEF added: 1 gallon Active/3.5-gallon Passive

Winter 2014/2015 was exceptionally cold and snow filled winter.
Miles since last Low DEF warning: 11155
Days since last Low DEF warning: 300
Odometer at Low DEF warning: 85279 miles
Date of Low DEF warning: 10/13/2015
Volume of DEF added: 1 gallon Active/4-gallon Passive

I made a few trips down to and back from Virginia the last half of 2015 and into 2016 along with a few trips to and from Connecticut. I did not operate the X5 from February to May 2016. In July 2016 I took the X5 cross-country and operated for about a month at higher elevations and high-desert temperatures.
Miles since last Low DEF warning: 13062
Days since last Low DEF warning: 300
Odometer at Low DEF warning: 98341 miles
Date of Low DEF warning: 8/8/2016
Volume of DEF added: 0.5 gallon Active/5.5-gallon Passive

From the end of 2016 through most of 2017, I drove up and down the East Coast about eight times and also had about a 20 mile commute every morning for most of those months.
Miles since last Low DEF warning: 12984
Days since last Low DEF warning: 290
Odometer at Low DEF warning: 111325
Date of Low DEF warning: 5/25/2017
Volume of DEF added: 1 gallon Active/5-gallon Passive

In June 2017, the Active tank and SCR supply/dosing module were replaced. October through December of 2017 I did not use the X5 at all. My thermostat began to very. very slowly shows signs of failure starting early 2018. I moved in April 2018 and now have an 80-mile round trip to work every morning.
Miles since last Low DEF warning: 15918
Days since last Low DEF warning: 442
Odometer at Low DEF warning: 127243 miles
Date of Low DEF warning: 8/10/2018
Volume of DEF added: 2.5 gallon Active/3.5-gallon Passive

My thermostats were replaced October 2018.

I only use BMW DEF. I figure it will take five to six gallons at any one time to top them off. The DEF is used at all times during operation and not just during regeneration. The actual consumption rate will depend on air temperature, engine temperature, catalyst temperature, “throttle” position, engine load, exhaust temperature, etc., which all effect emissions and NOx output.

FellowsheepTech 01-15-2019 06:33 PM

Excellent and helpful info - thank you! I had no idea it was that many gallons or used for other than regeneration.

josiahg52 01-16-2019 04:34 AM

Glad it is helpful. I don't know if urea is used for regeneration or not. I know urea is used to promote a specific reaction in the catalytic converter to reduce NOx. The DPF is regenerated by injecting extra diesel late in the injection cycle which raises the DPF temperature and oxidizes the accumulated soot mass. I think that's the active regeneration mode. Another method is to send NO2 through the DPF which somehow helps. Maybe that's the passive method? It might use urea for that. I don't know for sure how BMW does it.


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