How to make the n55 last?

[rollingSquare]

My F15 is on 140k miles now, I’d love for it to make it another 100k.

I’ve diligently done full synthetic oil/filter changes every 5k miles

I use Techron fuel system cleaner every month since I’ve heard gummed up high pressure fuel pump was an issue on some VINs.

Anything else I should look out for?

I’m thinking about changing the transfer case and diff fluids

And doing semi flushes on the ATF (drain what I can, refill with new fluid even though it won’t replenish all of the fluid in the Tran)

[F15_SGM]

https://f15.bimmerpost.com/forums/sh...5&postcount=19
https://f15.bimmerpost.com/forums/sh...2&postcount=22

Although at 140K, odo seems like your engine is already making its way up to 200K. Be careful with what you need to get done as one wrong installation, like not priming ofhg will the end.

[rollingSquare]

Originally Posted by F15_SGM

https://f15.bimmerpost.com/forums/sh...5&postcount=19
https://f15.bimmerpost.com/forums/sh...2&postcount=22

Although at 140K, odo seems like your engine is already making its way up to 200K. Be careful with what you need to get done as one wrong installation, like not priming ofhg will the end.

Geez, my x5 isn’t even worth $13k. Knock on wood my n55 has been running great so far, no oil leaks or anything, even at 140k miles.
Thanks for the heads up! I’d get sticker shock if something did happen and got a quote on repairs

[tlow98]

Change the diff, trans, and most importantly the transfer case fluids. You should be pretty good if you stay on top of that stuff.

[yupetc]

Besides regular oil intervals, and do change your ZF trans fluid at 100k mile mark.

Keep a keen eye on those common leaky places:

1. Valvecover Gasket
2. OFHG
3. Front Main Seal
4. Oil Pan Gasket


Then look out for signs of PCV failure. I'm routinely replacing OEM valvecover at every 50k miles just to ensure PCV and anything with that plastic valvecover be addressed.

Also replace your "mickey mouse" coolant return flange if you haven't done so. We typically go with the aluminum ones and you'll never have to deal with it again. OEM is plastic and it's destined to crack and fail.

After the above, look out for coolant leaks, be weary of coolant pump failure. I replace my coolant pump at 80k intervals. My X5 is at 192k miles right now, running like a champ, although at 185k mark, I took the motor out for a full forged internal build; I expect mine to go for another 200k miles if I don't sell it to indulge the newer gen's updated techs.

[Hashtag]

Impressive amount of miles. Any repairs or things aren't considered maintenance that you've encountered with getting to 140k?

[rollingSquare]

Originally Posted by Hashtag

Impressive amount of miles. Any repairs or things aren't considered maintenance that you've encountered with getting to 140k?

Nope, just oil, filter, brakes.
No leaks or any issues so far, which is why I’m getting nervous seeing how others change out valve covers, do tear downs, etc etc before they even reach 100k

[E90convert]

Nice to hear such that your vehicle is lasting awhile without issue! The 5k OCI and fuel system cleaner probably attribute to a top running engine. Consider that ZF Aftermarket recommends changing the trans oil and filter at 150k KM (~93k miles). I’ve also read some technical literature from BMW on the transfer case that they recommend changing the fluid at 100k miles. The service won’t show up to the user, but it will be indicated to the dealership when they check for maintenance codes. As far as the differentials go… I don’t think they need changed ever unless you’re towing a lot and getting them hot. If you’re just driving the vehicle, lifetime fill is probably fine. I assume you’re on the original coolant still? BMW rates it as long-term. But reading a lot of different owners manuals… the longest I’ve seen is 150k/10 years. I’d probably change it out too, but at a lower priority when compared to the transmission and transfer case.

[E90convert]

Originally Posted by yupetc

Besides regular oil intervals, and do change your ZF trans fluid at 100k mile mark.

Keep a keen eye on those common leaky places:

1. Valvecover Gasket
2. OFHG
3. Front Main Seal
4. Oil Pan Gasket


Then look out for signs of PCV failure. I'm routinely replacing OEM valvecover at every 50k miles just to ensure PCV and anything with that plastic valvecover be addressed.

Also replace your "mickey mouse" coolant return flange if you haven't done so. We typically go with the aluminum ones and you'll never have to deal with it again. OEM is plastic and it's destined to crack and fail.

After the above, look out for coolant leaks, be weary of coolant pump failure. I replace my coolant pump at 80k intervals. My X5 is at 192k miles right now, running like a champ, although at 185k mark, I took the motor out for a full forged internal build; I expect mine to go for another 200k miles if I don't sell it to indulge the newer gen's updated techs.

Agreed on the PCV system in the valve cover. On my previous 335i N55, it was replaced under warranty, I assume for the same reason. Also owned an N54 that started pissing oil out of the rear main seal because the PCV got clogged at around 130k miles. The plastic coolant overflow line also broke around 95k. I think the X5 has a stout rubber line though!

[Hashtag]

Impressive. I've already had to repair the oil housing and valve cover gasket at around 85k miles

I'm at 95K miles and I'm contemplating if I should get the water pump replaced as a precaution.

Originally Posted by rollingSquare

Nope, just oil, filter, brakes.
No leaks or any issues so far, which is why I’m getting nervous seeing how others change out valve covers, do tear downs, etc etc before they even reach 100k

[cfm56d7b]

Originally Posted by yupetc

Besides regular oil intervals, and do change your ZF trans fluid at 100k mile mark.

Keep a keen eye on those common leaky places:

1. Valvecover Gasket
2. OFHG
3. Front Main Seal
4. Oil Pan Gasket


Then look out for signs of PCV failure. I'm routinely replacing OEM valvecover at every 50k miles just to ensure PCV and anything with that plastic valvecover be addressed.

Also replace your "mickey mouse" coolant return flange if you haven't done so. We typically go with the aluminum ones and you'll never have to deal with it again. OEM is plastic and it's destined to crack and fail.

After the above, look out for coolant leaks, be weary of coolant pump failure. I replace my coolant pump at 80k intervals. My X5 is at 192k miles right now, running like a champ, although at 185k mark, I took the motor out for a full forged internal build; I expect mine to go for another 200k miles if I don't sell it to indulge the newer gen's updated techs.

yupetc By any chance, do you know the part number + source for aluminum coolant return flange? Any insights when the OEM one tends to fail?

PS. Our 2015 X5 N55 family vehicle has only 35.5K miles.

[imr3n]

+1 on the OFHG. There are 2 gaskets involved, so replace both of them if you see a leak on even one, just to be on the safe side.

[yupetc]

Originally Posted by cfm56d7b

yupetc By any chance, do you know the part number + source for aluminum coolant return flange? Any insights when the OEM one tends to fail?

PS. Our 2015 X5 N55 family vehicle has only 35.5K miles.

Yes, here it is:

https://www.amazon.com/Automotive-CH...s%2C122&sr=8-2

Very popular piece to locate easily. If you type in "N55 Coolant Flange", you'll come across many of them. If you want to be safe and get something of a quality brand, go for Rein and Dorman, I install about 10 of these per year for all the N55 motors that comes in and out of my garage, fitment is perfect from these two brands.

In terms of when to do it, I've seen one embrittled as low as 45k miles. Was doing the front main seal for that guy and one small tuck away by handling that hose, the plastic flange snapped right off. Let me say this: at 45k miles his flange may still be functioning fine until I yanked the hose and cause it to break, but let's also suspect that the measly designed plastic flange is likely on its way out and any shake, juke, vibration may just kill it. It's his good luck that I found it while doing a repair; much better than him driving around town and having it snap off the port, and left stranded on the side of the road.

[cfm56d7b]

Originally Posted by yupetc

Yes, here it is:

https://www.amazon.com/Automotive-CH...s%2C122&sr=8-2

Very popular piece to locate easily. If you type in "N55 Coolant Flange", you'll come across many of them. If you want to be safe and get something of a quality brand, go for Rein and Dorman, I install about 10 of these per year for all the N55 motors that comes in and out of my garage, fitment is perfect from these two brands.

In terms of when to do it, I've seen one embrittled as low as 45k miles. Was doing the front main seal for that guy and one small tuck away by handling that hose, the plastic flange snapped right off. Let me say this: at 45k miles his flange may still be functioning fine until I yanked the hose and cause it to break, but let's also suspect that the measly designed plastic flange is likely on its way out and any shake, juke, vibration may just kill it. It's his good luck that I found it while doing a repair; much better than him driving around town and having it snap off the port, and left stranded on the side of the road.

Cannot thank you enough. Great recommendation!

[Bruce322]

my 2014 x5 also just reached 140K miles this week.

I owned mine since new, I was a little worried about the maintenance and was planning to sell it in 2019. But due to car shortage and reduced travel, it is still in my garage and still running flawlessly.

I wasn't super on top of oil changes, did engine oil every 9000-10000 miles, and only changed brake fluid every 2-3 years.

Only big repair was OFHG & Valve cover, cost me about $1900 total done by the dealer at about 120,000 miles.

I later replaced the serpentine belt(the old one was in great condition after I took it off). All pads and rotors, transmission oil, transfer case oil, spark plug and ignition coil by myself, planning to keep this car for long term.

Some say Vanos, oil pan gasket, oil pump can go bad after 50k to 100k miles, but I think I will wait for sign of failure before I replace them.