[The Nightman]

Originally Posted by Hakentt

here is what I was talking about:

Thanks for sharing, you're not wrong about some things. I like the N52 but won't deny there are some issues with it. Everyone's entitled to their opinion on the N52 but let's keep this thread focused on the flakes and peeling coating.

Would love to see more information about the peeling coating if possible. Is it only on the magnesium parts?

[sonofsun]

Efthreeoh " Traditionally, the leaking coolant smell is the sign to the owner the waterpump needs attention"

What does this mean? I replaced my coolant pump, thermostat and other hoses but feels like I smell a faint trace of coolant but nothing is leaking anywhere.

The coolant tank shows no oily sheen, engine oil shows nothing shiny, exhaust isn't very white or anything. Or were you talking about traditional designs where waterpumps are belt driven.

[Efthreeoh]

Originally Posted by sonofsun

Efthreeoh " Traditionally, the leaking coolant smell is the sign to the owner the waterpump needs attention"

What does this mean? I replaced my coolant pump, thermostat and other hoses but feels like I smell a faint trace of coolant but nothing is leaking anywhere.

The coolant tank shows no oily sheen, engine oil shows nothing shiny, exhaust isn't very white or anything. Or were you talking about traditional designs where waterpumps are belt driven.

Traditional belt-driven waterpump designs. Not every belt pump was/is made this way, but back in the day many designs included a weep hole in the housing between the impeller shaft seal and the shaft bearing (a small cavity space in the housing casting) which allowed a small amount of coolant to leak out. It served as a warning (by the slight aroma of hot coolant) that the waterpump inner seal had started to leak and would eventually contaminate the outer bearing and cause it to fail.

[Efthreeoh]

Originally Posted by The Nightman

The other two threads I linked to involves a 2011 128i and a 2007 X3, so if it's across the board if it's a manufacturing defect.

My E90 was a 2006 and it never had flakes in the filter that I saw; though, I've never cut one open. Nor when I removed the oil pan at 10 years and 293,000 miles, there were no flakes. I pulled and replaced the VANOS check valves at 305,000 miles and they were clean as if new.

My Z4 is a 2008. Next oil change, probably in 12 months from now, I'll check the oil filter. Maybe out of curiosity, I'll remove the oil filter and inspect it. The Z4's N52 is now 17 years old and 123,000 miles. Up until now I've seen no evidence of flakes. I use(d) only BMW oil and OE/OEM oil filters in my N52s. As I said, the E90's lifetime OCI was 12,300 miles. The Z4 lifetime OCI is at 8,500.

While some N52s may have the flaking condition, no one here has directly tied the flaking to an engine failure (via oil starvation). I would think if the flaking were clogging the internals of the oil system the oil pressure would be affected and trigger the low oil pressure warning.

I mean, we're here with N52s that are in use now some 12 years past last production date, with a lot of the N52 population well past 15 to just nearly over 20 years old and the flaking issue is now coming to light, to the point one member says the N52 is "junk". I've been an active member of E90 since 2006 and never heard of N52 flaking and resultant engine failures until this past month. I'll stand by my position that the N52 is one of BMW's best inline-6's it has ever produced. At 426,000 miles in 2025, the N52 in my E90 was still returning over 27 MPG just as it did when it was brand new in 2006. Hakentt can call the N52 junk all he wants, but he has a lot of work to do to convince me and most of us N52 owners that the engine is junk. I think his accusation is hilarious.

[The Nightman]

Originally Posted by The Nightman

Based on the photos of the flakes in the filter in this thread, as well as the two threads linked here (with photos of the peeling coating), I assume they share the same cause.

Looking at various used N52 blocks on eBay, they do not exhibit the same "golden" coating as found in the above threads with the peeling coating.

Reading through this paper on the manufacturing of the N52 engine, there is no mention of a coating used on the AJ62 magnesium alloy.

The peeling coating does not seem to be a common issue; if it was, I think we would see a lot more incident reports.


So I do not think the peeling coating/flakes are a design or manufacturing defect/issue with the N52 engine. Without knowing the full history of the engines with the flakes, we can only speculate. Given these engine's propensity to leak oil, I wonder if a previous owner used some type of engine stop leak additive, which coated the engine and is now peeling off?

Thanks for attending my TED Talk.

I reached out to Michael Höschl, one of the authors of the above paper, and he was kind enough to confirm that the magnesium parts have no coating:

I highly appreciate your interest in „our" technology. But I have to admit that despite of giving the speech I am not the expert on the technical details. Nevertheless I can confirm that there is no coating at all on the magnesium part.

For further details I would like you to contact my (former) BMW colleague Wolfram Wagener who edited the paper for me.

So the flakes and peeling coating is from something else. My best guess is still some kind of oil stop leak additive.

[StradaRedlands]

Originally Posted by Efthreeoh

Traditional belt-driven waterpump designs. Not every belt pump was/is made this way, but back in the day many designs included a weep hole in the housing between the impeller shaft seal and the shaft bearing (a small cavity space in the housing casting) which allowed a small amount of coolant to leak out. It served as a warning (by the slight aroma of hot coolant) that the waterpump inner seal had started to leak and would eventually contaminate the outer bearing and cause it to fail.

I believe the newest 4 and 6 cylinder BMW motors returned to pulley driven water pumps?

Originally Posted by The Nightman

I reached out to Michael Höschl, one of the authors of the above paper, and he was kind enough to confirm that the magnesium parts have no coating:



So the flakes and peeling coating is from something else. My best guess is still some kind of oil stop leak additive.

This is good content!!! Thanks for taking the time to track that information down!

[Efthreeoh]

Originally Posted by The Nightman

I reached out to Michael Höschl, one of the authors of the above paper, and he was kind enough to confirm that the magnesium parts have no coating:



So the flakes and peeling coating is from something else. My best guess is still some kind of oil stop leak additive.

Yes, thanks for digging up the information regarding the N52 and flakes. It never made any sense why a coating would be necessary on the inside of a magnesium engine block that is bathed in oil.

[Hakentt]

Originally Posted by Efthreeoh

Yes, thanks for digging up the information regarding the N52 and flakes. It never made any sense why a coating would be necessary on the inside of a magnesium engine block that is bathed in oil.

People have opinions, but facts are facts.
"Magnesium block coatings are essential surface treatments that protect highly reactive magnesium from corrosion and wear, using methods like Plasma Electrolytic Oxidation (PEO), anodizing, or ceramic coatings (Cerakote) to create hard, durable, barrier layers. These coatings, often metal oxides, phosphates, or advanced ceramics, seal the surface, prevent oxidation, improve wear resistance for automotive/aerospace parts, and can even be self-healing for long-term protection, overcoming magnesium's inherent reactivity. "

[NZE90]

Originally Posted by Hakentt

People have opinions, but facts are facts.
"Magnesium block coatings are essential surface treatments that protect highly reactive magnesium from corrosion and wear, using methods like Plasma Electrolytic Oxidation (PEO), anodizing, or ceramic coatings (Cerakote) to create hard, durable, barrier layers. These coatings, often metal oxides, phosphates, or advanced ceramics, seal the surface, prevent oxidation, improve wear resistance for automotive/aerospace parts, and can even be self-healing for long-term protection, overcoming magnesium's inherent reactivity. "

And the source of your "facts" is? I've been an Automotive Engineer/Electrician for 32 years and worked for BMW for 10+ of those years, repaired hundreds and hundreds of valve cover and sump gasket leaks on these engines from their shitty gaskets, and NEVER come across this mystical coating you speak of.

Also owned lots of N52 powered cars which i always cut the oil filters open on. Again, never come across this mystical coating. If they do suffer from this condition, then it's certainly NOT ALL OF THEM as you elude to. It's a small minority.
Yes, they have shitty gaskets, ALL BMWs do, yes the early engines had steel ledge seals that SOMETIMES cause an issue, NOT always, I've never had any issues at all with any of my 9 + N52 cars I've owned. Plenty of issues with the V8 and N54 ones though.

[hassmaschine]

no water internally contacts the magnesium block of the N52. the inner block is aluminum.. and oil doesn't react with magnesium. so what would be the purpose of this imaginary coating?

[Efthreeoh]

Originally Posted by Hakentt

People have opinions, but facts are facts.
"Magnesium block coatings are essential surface treatments that protect highly reactive magnesium from corrosion and wear, using methods like Plasma Electrolytic Oxidation (PEO), anodizing, or ceramic coatings (Cerakote) to create hard, durable, barrier layers. These coatings, often metal oxides, phosphates, or advanced ceramics, seal the surface, prevent oxidation, improve wear resistance for automotive/aerospace parts, and can even be self-healing for long-term protection, overcoming magnesium's inherent reactivity. "

Here is the description of the N52's engine block from BMW's N52 technician training manual:

Crankcase
Since magnesium cannot be used in all areas of engine construction, the new N52 crankcase is a composite design. The crankcase consists of an aluminum/silicon insert which is cast inseparably in a magnesium alloy. The crankcase is a two-piece design with a separate bedplate also cast from magnesium. Also, a notable change from previous designs is the timing cover which is now cast as an integral part of the engine block. The aluminum silicon insert provides the threaded connections for the transmission mounting, cylinder head and crankshaft main bolts. The insert provides the coolant passages as well. This is to prevent coolant contact with the magnesium portion of the engine block.

The use of magnesium is a new concept for production passenger vehicles. BMW has developed special processes for the development of the N52 crankcase. A special magnesium alloy (AJ62) is used which has excellent properties which reduce the possibility of corrosion and allow favorable machining characteristics.

The cylinder bore consists of an Alusil structure; there are no iron cylinder liners as with previous 6-cylinder designs. The cylinder bores cannot be machined; however, this design still allows for planing of the deck surface if needed.

Bedplate
The N52 engine uses a split crankcase, the upper section is made from a composite magnesium/aluminum structure. The lower portion, which is used to increase rigidity, is designed as a bedplate structure made from magnesium.

There are sintered steel inlays for the main bearings to take up forces which would not be suitable for magnesium alone. Between the bedplate and crankcase, a liquid sealer is injected under high pressure into a machined groove This process is critical in service applications.

No mention of a coating required to reduce the corrosion resistance of the AJ62 mag alloy used for the N52. An internet search does not specifically address the need for coating AJ62 in an ICE use case. As far as I know, BMW is the only automotive manufacturer that uses a magnesium alloy for engine blocks. The outside surface of the N52 block does not have any type of coating that I have noticed. Were corrosion resistance a critical issue for the AJ62 alloy, certainly the outside of the N52 engine block would be coated since it is exposed to a highly corrosive environment. Again, where the inside of the engine block is constantly splashed/sprayed with engine oil and where very small amounts of water are present (until vaporized by heat), it appears the magnesium alloy developed for the N52 does not require a coating for corrosion protection.

[StradaRedlands]

People have opinions, but AI generated slop is AI generated slop...

[Hakentt]

Originally Posted by hassmaschine

no water internally contacts the magnesium block of the N52. the inner block is aluminum.. and oil doesn't react with magnesium. so what would be the purpose of this imaginary coating?

you love to talk smack about me but your question proves you don't know much about engines, maybe you should quit writing nonsense and read what Haken is writing and learn something.
When you take oil filler cap off the engine sometimes you will see white milky residue, that is condensation or moisture inside the crankcase, that is why when engine is heated up, the PCV system will evaporate it all into intake. That is why it is essential to avoid short daily trips with the car where the engine don't heat up completely.

[bmwbob89]

🍿 🍿 🍿

[hassmaschine]

Originally Posted by Hakentt

you love to talk smack about me but your question proves you don't know much about engines, maybe you should quit writing nonsense and read what Haken is writing and learn something.
When you take oil filler cap off the engine sometimes you will see white milky residue, that is condensation or moisture inside the crankcase, that is why when engine is heated up, the PCV system will evaporate it all into intake. That is why it is essential to avoid short daily trips with the car where the engine don't heat up completely.

[hassmaschine]

Originally Posted by StradaRedlands

People have opinions, but AI generated slop is AI generated slop...

there is no mention of a coating anywhere in any documentation from BMW, internal training manuals, repair manuals, TSBs, marketing materials, or otherwise.

[lookalikehuuh]

Originally Posted by Hakentt

People have opinions, but facts are facts.
"Magnesium block coatings are essential surface treatments that protect highly reactive magnesium from corrosion and wear, using methods like Plasma Electrolytic Oxidation (PEO), anodizing, or ceramic coatings (Cerakote) to create hard, durable, barrier layers. These coatings, often metal oxides, phosphates, or advanced ceramics, seal the surface, prevent oxidation, improve wear resistance for automotive/aerospace parts, and can even be self-healing for long-term protection, overcoming magnesium's inherent reactivity. "

"Mr Mechanic" just STFU, you are using material that is AI generated, has no bearing in real life and still insist that you know MORE than someone who literally was involved in the manufacturing of the engines as confirmed above.

How many SAE International papers have you written, had SAE approve and publish? How many magnesium engines have you cast from raw materials. How many engines have you designed from top to bottom and actually sent to a mass manufacturing plant to be built by the millions. I'm guessing NONE!

The proof is in the pudding, the guy that was employed by BMW, directly involved in the design and manufacturing process of the engine said there is NO COATING. Old timers around this place also confimed that we have never seen any issues like what you describe, nor have we experienced those failures in well over a million miles of combined miles.

Give it up! N52 is a very good engine, potentially one of the best to ever come out of germany from BMW, its not perfect nor the most powerful, but it definitely is a solid engine.

[tlow98]

Originally Posted by Hakentt

you love to talk smack about me but your question proves you don't know much about engines, maybe you should quit writing nonsense and read what Haken is writing and learn something.
When you take oil filler cap off the engine sometimes you will see white milky residue, that is condensation or moisture inside the crankcase, that is why when engine is heated up, the PCV system will evaporate it all into intake. That is why it is essential to avoid short daily trips with the car where the engine don't heat up completely.

Guy, just beat it already. You’re gonna need more than your imaginary rubber knife in this gun fight.

Yes, there’s condensation in the engine. What part of the specifically developed magnesium alloy that resists corrosion doesn’t work for you?

[hassmaschine]

It actually makes me a little sad (not that sad) that HakkenTT now relies on AI for his "facts". We go way back BTW - maybe he remembers when he tried to "secretly" sell me a pirated ROM from one of Mark D's custom E30 tunes, who I also happened to be friends with.. uhh.. guess how that went.

[lookalikehuuh]

Originally Posted by hassmaschine

It actually makes me a little sad (not that sad) that HakkenTT now relies on AI for his "facts". We go way back BTW - maybe he remembers when he tried to "secretly" sell me a pirated ROM from one of Mark D's custom E30 tunes, who I also happened to be friends with.. uhh.. guess how that went.

It suddenly ALL makes sense now.

[tlow98]

Originally Posted by hassmaschine

It actually makes me a little sad (not that sad) that HakkenTT now relies on AI for his "facts". We go way back BTW - maybe he remembers when he tried to "secretly" sell me a pirated ROM from one of Mark D's custom E30 tunes, who I also happened to be friends with.. uhh.. guess how that went.

Le sigh. Well, /thread.

Glad to see you on here, Hass

[Lochstar8]

Sorry I haven’t checked the thread in a while little busy this time of year.


Wow this uh…. Forum turned out a little differently than I would have thought.

But regardless interesting to see what has come up here and that I’m not the only one. Runnin'Rich your filters look basically identical to mine, albeit mine are more full then yours but the same material. I haven’t done my 5000km oil FILTER change yet but the car did just cross 340k km. Which at this point is well over 20,000km with this “material” showing up and no change in engine performance or noise. So whatever it is isn’t very critical to the engines wellbeing and I drive the piss out of my little 2.5 liter.


The Nightman

I reached out to Michael Höschl, one of the authors of the above paper, and he was kind enough to confirm that the magnesium parts have no coating: on the manufacturing of the N52 engine, there is no mention of a coating used on the AJ62 magnesium alloy.

So the flakes and peeling coating is from something else. My best guess is still some kind of oil stop leak additive.

I can 100% confirm “Stop Leak” was NEVER used in my engine so it has to be something else.

One thing I thought of is maybe it’s the additive packages within the oil itself building up inside the engine and breaking up over time. Which could be as a result of these engines having a relatively high operating temp potentially breaking down some of the oil which causes deposits. But you’d think you’d see similar problems on N55 or even N54 cars.

Or maybe at some point a small amount of coolant from a oil filter housing leak got into the engine and solidified and is breaking up but that seams unlikely to me.

And Runnin'Rich I’d be happy to chip in on a black stone analysis.
Or hell I’ll send one out on my next oil change but that may take a while depending on things so who’s ever comes first I guess.