Considering high mileage F15 diesel

[RockDriver]

Considering buying high mileage F15 diesel, most likely 30D. We're talking 100-150K miles. Place of action is UK. Available advertised options mostly state full or partial service history. Budget up to £15K.

So to start with I'm familiar with the whole high cost of maintenance song as this would be my 4th BMW and second X5. I'm not concerned about spending a few grand a year in maintenance costs. What I am concerned about is the likelihood of catastrophic failure costing 5 figures to repair.

Here in UK we have some level of consumer protection, meaning basically if the car was bought from a dealer with a pre-existing condition - the dealer has to take responsibility for it within 6 months of purchase. I have been in this situation recently when the V8 engine of my E70 was diagnosed with head gasket failure within a month of buying and I was quoted 12K for engine replacement. The dealer took the car back.

So the main concern here is the two most expensive components - engine and transmission. I understand the whole emissions system can be expensive to repair too?

From what I read so far, both the engine and gearbox seem to be rather reliable. There's some conflicting information about the transmission and the fluid change intervals. I've seen wildly varying statements:

• "OMG if transmission wasn't serviced at 80K miles max, it's beyond saving!"
• It's OK to service the transmission even if the mileage is over 100K.
• BMW official stance is that transmission doesn't have to be serviced at all.

My guess is the middle option is still realistic.

Some reports regarding the engine. CP4 pump failure seems more related to US and Eastern Europe, having to do with different diesel fuel properties, as I'm in UK I assume I'm good. Timing chain normally should last to at least 150-200K miles.

Anyway, thoughts?

[stocktree]

Biggest issues with the diesels are egr and timing chains.

[E85 Sport]

Originally Posted by RockDriver

What I am concerned about is the likelihood of catastrophic failure costing 5 figures to repair.

Potentially costly repairs on F15:
timing chains,
CP4 fuel pump,
front driveshaft

Noteworthy but not a major concern:
transmission,
emissions system

Timing chains
Anecdotally in USA many enthusiasts feel that extended oil change intervals (OCI) of ten thousand miles, and short urban drive cycles, can hasten timing chain wear. It is a labor-intensive engine-out repair because the timing chains are located at the rear of the engine.

General consensus among enthusiasts wanting to keep their N57 healthy for long-term ownership is:
A) perform oil changes more frequently, e.g. every 6,000 miles; and,
B) disable the "automatic stop/start" feature to keep the engine running uninterrupted

CP4 fuel pump
If it fails, shrapnel contaminates the lines, tank, injectors. Everything must be replaced. Failure rate is much lower on the revised/updated pump with set screws.

Front driveshaft
E70 and now F15 can experience front driveshaft failure. If it fails, it can damage nearby components: transfer case, transmission, oil pan. This can be very costly. It is recommended to inspect the front driveshaft for evidence of corrosion and/or wobble in the splines. An American member of this forum, named Tony, sells a replacement driveshaft with longer splines to address one of the factors that lead to premature failure. "Front driveshaft?" post #31

These next two are noteworthy but unlikely to require costly repair:

Transmission service
Service the transmission over 100k miles. The transmission manufacturer recommends it. Ignore BMW stance -- BMW says lifetime fill because they stopped doing free filter replacements.

Emissions system
Short answer: The system is quite durable. There are many OBD2 smartphone apps to monitor the engine's health, diagnose error codes, etc. DPF is costly if it gets clogged and needs to be cleaned or replaced, but this rarely happens.
Longer answer: In USA many enthusiasts proactively remove fully-functioning emissions systems because they believe it is failure-prone. Honestly, the real reason they remove it is because they prefer the performance gains that come from a turbo-back straight-pipe exhaust running higher boost levels. The downside is smell and smoke from tailpipes (some are more smokey than others). If you desire increased performance, there are upgrade "tunes" that provide a modest increase in power while keep the emissions system intact thereby avoiding smell and smoke.

[E85 Sport]

Originally Posted by stocktree

Biggest issues with the diesels are egr and timing chains.

What is the EGR issue?

Edit: Probably referring to the North American recall due to EGR cooler cracking:
New (Nov 2021) EGR recall for 2014-2017 X5 diesel

[RockDriver]

Originally Posted by RockDriver

Considering buying high mileage F15 diesel, most likely 30D. We're talking 100-150K miles. Place of action is UK. Available advertised options mostly state full or partial service history. Budget up to £15K.

So to start with I'm familiar with the whole high cost of maintenance song as this would be my 4th BMW and second X5. I'm not concerned about spending a few grand a year in maintenance costs. What I am concerned about is the likelihood of catastrophic failure costing 5 figures to repair.

Here in UK we have some level of consumer protection, meaning basically if the car was bought from a dealer with a pre-existing condition - the dealer has to take responsibility for it within 6 months of purchase. I have been in this situation recently when the V8 engine of my E70 was diagnosed with head gasket failure within a month of buying and I was quoted 12K for engine replacement. The dealer took the car back.

So the main concern here is the two most expensive components - engine and transmission. I understand the whole emissions system can be expensive to repair too?

From what I read so far, both the engine and gearbox seem to be rather reliable. There's some conflicting information about the transmission and the fluid change intervals. I've seen wildly varying statements:

• "OMG if transmission wasn't serviced at 80K miles max, it's beyond saving!"
• It's OK to service the transmission even if the mileage is over 100K.
• BMW official stance is that transmission doesn't have to be serviced at all.

My guess is the middle option is still realistic.

Some reports regarding the engine. CP4 pump failure seems more related to US and Eastern Europe, having to do with different diesel fuel properties, as I'm in UK I assume I'm good. Timing chain normally should last to at least 150-200K miles.

Anyway, thoughts?

Thanks for detailed response. This more or less aligns with my own analysis.

Just to summarize my assumptions so far:

Timing chain. Should normally last 150-200K, frequent oil changes recommended and listening to the engine for early signs of timing chain failure. And yeah, I'd disable that autostart crap first thing, it annoys the hell out of me.

CP4 fuel pump. Probably low risk in my case, since I'm in Western Europe and most cases were reported in US and Eastern Europe due to different diesel chemistry that has less lubricating effect.

Front drive shaft. This one is new to me. I've watched the video. So getting the car on a ramp and inspecting the drive shaft for play should be done. After buying, would be consider replacing the drive shaft with the enhanced version.

Transmission. If the service hasn't been done on it already, perform it after purchasing the car.

Emissions system. Good advice on the OBD2 dongle and app - I'd get that after buying the car. I did also read that cleaning the DPF is an option and only costs a few hundred. Disabling the emissions system in UK is a big no-no though. The car would fail the MOT (mandatory annual vehicle check in UK) and you could get slapped with a fine. Also I live in London and the mayor here is a hardcore emission nazi, having declared a total war on non-compliant cars.

So I think overall taking all the precautions and with a bit of luck I should be able to reduce the risk to manageable level. Also as mentioned already, I do have a certain period of protection after buying the car where I can challenge the dealer in an event of a serious break down.

[crystalworks]

Originally Posted by RockDriver

Considering buying high mileage F15 diesel, most likely 30D. We're talking 100-150K miles. Place of action is UK. Available advertised options mostly state full or partial service history. Budget up to £15K...

Anyway, thoughts?

I wouldn't worry too much about the chain. That's a real concern with the 4 cylinder diesels. The N57, with regular oil changes and maybe a replacement tensioner(s) should be fine into high mileage. Our M57 was perfect when we sold it at 170,000 miles.

Transmission, service it with Valvoline Maxlife Multivehicle Full synth if you guys get it over there. Saved 2 different ZF transmissions with the stuff. One at 120,000 miles and one at 190,000 miles.

Driveshaft, if there is wear in the diff splines, get the enhanced one. If not, a regular replacement will do. Replaced ours at 108k with the Febi version.

If the engine and trans are currently in good condition. The only real gotcha might be the emissions stuff... and the HPFP which you mentioned not being as big a concern in the UK.

Good luck and happy hunting.

[smyles]

M57 experience is (mostly) irrelevant to N57, especially re chains wear. Two completely different engines.

In N57, you can assess the main chain condition with a special measuring tool that screws into the tensioners hole. Any rattling sounds indicate almost immediate need for replacement. Which, I'm guessing, is a much familiar procedure to EU mechanics and shouldn't be as costly as here in US.

[crystalworks]

Originally Posted by smyles

M57 experience is (mostly) irrelevant to N57, especially re chains wear. Two completely different engines.

In N57, you can assess the main chain condition with a special measuring tool that screws into the tensioners hole. Any rattling sounds indicate almost immediate need for replacement. Which, I'm guessing, is a much familiar procedure to EU mechanics and shouldn't be as costly as here in US.

Interesting. I thought it was a fairly derivative engine. I wonder what makes the N57 chain a worse setup than the M57 in terms of wear? They look very similar, other than their location obviously.

You are right in that it seems the EU techs would be much more competent with this and familiar. Reading some of the comments in below video though, most seem to agree that with regular/reasonable OCIs the chain can last well into the car's life. One completely anecdotal data point, ours has 109k miles on it and exhibits no chain rattle. But that is just one data point obviously.

https://www.youtube.com/watch?v=LZx3rs6qkc4





Self edit: Seems the chain itself might be the culprit rather than the system itself.

Sorry OP for the semi off topic discussion. Just interested as I doubt our X5 is the last BMW we'll own with the N57. Rather keen on the F10 5ers.

[RockDriver]

Originally Posted by crystalworks

Interesting. I thought it was a fairly derivative engine. I wonder what makes the N57 chain a worse setup than the M57 in terms of wear? They look very similar, other than their location obviously.

You are right in that it seems the EU techs would be much more competent with this and familiar. Reading some of the comments in below video though, most seem to agree that with regular/reasonable OCIs the chain can last well into the car's life. One completely anecdotal data point, ours has 109k miles on it and exhibits no chain rattle. But that is just one data point obviously.

https://www.youtube.com/watch?v=LZx3rs6qkc4

Attachment 3340255

Attachment 3340256

Self edit: Seems the chain itself might be the culprit rather than the system itself.

Sorry OP for the semi off topic discussion. Just interested as I doubt our X5 is the last BMW we'll own with the N57. Rather keen on the F10 5ers.

No worries, in fact any such related information is welcome.

On the same subject, viewed a 30D recently, got it up on a ramp and sure enough - the front drive shaft had play. I'm starting to suspect that most of the F15s at this mileage will have it.

But another thing I saw was crank shaft seal oil leak. Now this one does have to do with the N57 engine. The garage didn't specialize in BMWs, so they only guessed that to replace the seal, at the very least transmission would have to be dropped, maybe even the engine (probably not). Another potentially expensive repair point of N57? I don't know.

[crystalworks]

Originally Posted by RockDriver

On the same subject, viewed a 30D recently, got it up on a ramp and sure enough - the front drive shaft had play. I'm starting to suspect that most of the F15s at this mileage will have it.

You know, I'd be curious to know how a very low mileage F15's front driveshaft feels. I replaced our front shaft, but am tempted to get under there just to feel the play at the transfer case.

Ahhhhh BMW... always with the "gotchas" on every platform.

[///d]

Now you've got me wanting to check the driveshaft. Thats an issue I was not aware of.

I've been thinking about doing the timing chain soon. Just rolled 110k but I have zero reason to suspect issues yet outside of just preventative maintenance. Already planning a carbon cleaning so half the motor will be apart anyways, might as well just do it all.

[RockDriver]

Originally Posted by crystalworks

You know, I'd be curious to know how a very low mileage F15's front driveshaft feels. I replaced our front shaft, but am tempted to get under there just to feel the play at the transfer case.

Ahhhhh BMW... always with the "gotchas" on every platform.

So in the last couple of days I've looked at 3 cars. Got each one of them up on a ramp and rattled the front drive shaft with my own hands. They all had some play, nothing dramatic though. I don't know, I'm starting to think that maybe some play is normal.

Originally Posted by ///d

Now you've got me wanting to check the driveshaft. Thats an issue I was not aware of.

I've been thinking about doing the timing chain soon. Just rolled 110k but I have zero reason to suspect issues yet outside of just preventative maintenance. Already planning a carbon cleaning so half the motor will be apart anyways, might as well just do it all.

I spoke to a mechanic about the timing chain and he said I shouldn't worry about the chain before at least 150K miles, unless it starts rattling. He confirmed that changing it doesn't require dropping the engine either, so that's a good thing.

Yeah, that drive shaft is a bit of a wildcard from what I've seen so far. There's another thread related to it and there's a guy who has designed an upgraded version of the shaft and on top of that a custom protective sleeve. Many of these guys have the X5Ms though, so they have a lot more to loose.

I think I'm gonna buy the least beat up F15 I've checked out, drive it for a month, then decide what to do about the drive shaft. There's a certain period of time when the dealer is responsible for repairs if something goes horribly wrong and I've already exercised that right in the past.

[E85 Sport]

For future readers, here is another help thread:

Diesel Information Thread