[fatty335]

I, as a great many of you, have been following the seemingly growing number of n55 engine failures following an OFHG change (sorry pete_gpx). As the owner of two n55 equipped vehicles (2011 e90 335i and 2014 F25 35i), and someone who does all his own maintenance, this concerns me. Many on this and other forums have weighed in on what they think is happening but there seems to be no agreement on the root cause. The three leading theories are:

1. Introducing a large air bubble that the oil pump cannot clear
2. Introducing some foreign matter into the exposed unfiltered oil passage
3. Momentary oil starvation at startup that finally causes already worn bearings to expire

While changing the oil pan gasket on my wife’s 2014 X3 recently, I noticed the oil pump in her car was of a different design than the one in my car – I had mine off earlier this year while preventatively replacing the rod bearings. Yes, I know, I’m a car nerd who notices these kinds of things. So I got curious and looked it up. According to realOEM, for the e90, the “old style” n55 oil pump – 11417573747 – was introduced with build date 02/2010; I don’t know if this part number was in use in other models that got the n55 earlier. With build date 08/2011, a “new style” n55 oil pump – 11417613549 – was introduced right at the end of e90 production. As far as I can tell, this new style pump remained in production across model ranges until the end of n55 production. These pumps are not interchangeable and there are some noteworthy design differences visible from the outside. The most noticeable is the center section that is attached to the rotor – it appears to house a bearing and is of a significantly larger diameter on the new style pump. Additionally, there are far more stiffening ribs (10 versus 4) supporting the center section on the new style pump. This leads me to believe a BMW engineer saw the need for serious stiffening and beefing up of the center section of the oil pump shortly after introduction of the n55. Perhaps they discovered an issue with the 2010/11 pump design? I’m certainly not saying this is in any way causal to engine failures following an OFHG change, but it does represent a difference in the oiling systems of early n55 engines versus later models with the n55. Perhaps a tech or indy shop owner who has old and a new style oil pumps lying around would be willing to open them up to see what the internal differences are?

Old Pump Front:


New Pump Front:


Old Pump Back:


New Pump Back:

[TheMidnightNarwhal]

The N54 pump is also same smaller one though. EDIT: I mean the hole that houses the bearing thing, it's same size as N54 to early N55.

N54 pump

[TheGoodTheBadTheUgly]

The N54 pump and feeding system differs and this is why I always said and thought that it was pump related. The only thing that disturbs me is that I never heard of a failure while dealer technician's are servicing an OFHG. If you know of any, please correct me

[TheMidnightNarwhal]

Originally Posted by TheGoodTheBadTheUgly

The N54 pump and feeding system differs and this is why I always said and thought that it was pump related. The only thing that disturbs me is that I never heard of a failure while dealer technician's are servicing an OFHG. If you know of any, please correct me

BMW Techs on Reddit have said in a thread that they just do the priming thing for BMW warranty related paperwork. If they prime the system and it still fails, then the fault doesn't rely on the tech. They said it still happens. But that was only from 2 techs so.

[ferocity02]

Debris in the oil passage is the only theory that makes sense. The housing drains itself when the engine is off, so the other 2 theories happen all the time. I changed mine and all I did was fill the oil filter area with oil before buttoning it up. I didn't do any priming.

[Pladi]

Originally Posted by ferocity02

Debris in the oil passage is the only theory that makes sense. The housing drains itself when the engine is off, so the other 2 theories happen all the time. I changed mine and all I did was fill the oil filter area with oil before buttoning it up. I didn't do any priming.

Agree but

The part where the debris theory fails at, is the fact that most inline 6 bmw engines have that type of housing. Why are they not siezing after OFHG..

[bbnks2]

lol more conspiracy theories

[bbnks2]

Originally Posted by Pladi

Agree but

The part where the debris theory fails at, is the fact that most inline 6 bmw engines have that type of housing. Why are they not siezing after OFHG..

This is false. E8x/E9x was first generation of this OFH. E46 had a much different, albeit similar concept, housing.

Further, this does happen on N54s: https://www.n54tech.com/forums/showthread.php?t=57495

There are a few example posted across various forums. You just don't have people scrambling to forums to complain about it because N54's aren't worth crap and you can buy a used engine for like $1500 now. N55's were put int vehicles all the way out to 2017... plenty of them are still worth big money and still under factory warranty.

[whyzee125]

Originally Posted by Pladi

Agree but

The part where the debris theory fails at, is the fact that most inline 6 bmw engines have that type of housing. Why are they not siezing after OFHG..

I was reading another older thread about N55's blowing up left and right and you were adamantly of the belief that there is no n55 rod bearing issue. Are you now of the belief that there is an issue?

[Pladi]

Originally Posted by bbnks2

This is false. E8x/E9x was first generation of this OFH. E46 had a much different, albeit similar concept, housing.

Further, this does happen on N54s: https://www.n54tech.com/forums/showthread.php?t=57495

There are a few example posted across various forums. You just don't have people scrambling to forums to complain about it because N54's aren't worth crap and you can buy a used engine for like $1500 now. N55's were put int vehicles all the way out to 2017... plenty of them are still worth big money and still under factory warranty.

I am saying the same thing.. whats false about my comment..

If its the debris that is causing this we would see a wider distribution of this type of failure.

[Pladi]

Originally Posted by whyzee125

I was reading another older thread about N55's blowing up left and right and you were adamantly of the belief that there is no n55 rod bearing issue. Are you now of the belief that there is an issue?

Its clearly an oiling issue . I dont think its the bearing.

We could have a few different root causes here mixed up. I am reffering specifically to this seize after OFHG work.

[whyzee125]

Originally Posted by Pladi

Its clearly an oiling issue . I dont think its the bearing.

We could have a few different root causes here mixed up. I am reffering specifically to this seize after OFHG work.

Interesting. To your knowledge if I've done my OFHG successfully should I be good until next time it leaks? Lol

[Pladi]

Originally Posted by whyzee125

Interesting. To your knowledge if I've done my OFHG successfully should I be good until next time it leaks? Lol

I have done this work 2 times and my car falls under this early prod date...

And I have not had this issue. ITs impossible to know if we will ever have issues. This occurrence is so random and no one can explain why its happening..

[drwillb]

Originally Posted by Pladi

I have done this work 2 times and my car falls under this early prod date...

And I have not had this issue. ITs impossible to know if we will ever have issues. This occurrence is so random and no one can explain why its happening..

Bad pump design or bad bearing design would lead to less random/more frequent seizures.

Random debris in the oiling system would lead to infrequent seizures.

That's how I see it.

[TheMidnightNarwhal]

Originally Posted by Pladi

I have done this work 2 times and my car falls under this early prod date...

And I have not had this issue. ITs impossible to know if we will ever have issues. This occurrence is so random and no one can explain why its happening..

I've done mine 2 times as well but I am N54. First time I did not prime it 2nd time I knew about the priming and did it for good measure.

[Pladi]

Originally Posted by drwillb

Bad pump design or bad bearing design would lead to less random/more frequent seizures.

Random debris in the oiling system would lead to infrequent seizures.

That's how I see it.

Sounds logical enough.

What I know for sure at this point is that we will I think never know for sure. Unless BMW admits to something or a suspicious TSB is released. .

[Pladi]

Originally Posted by TheMidnightNarwhal

I've done mine 2 times as well but I am N54. First time I did not prime it 2nd time I knew about the priming and did it for good measure.

Ur the N54 guy that keeps teasing us prone n55 guys lool

I know that a few well respected members will always refuse that this issue is specific to N55.

Personally I am convinced that early n55s are more prone to this issue for whatever reason.

[feuer]

Originally Posted by ferocity02

The housing drains itself when the engine is off

Not completely. There is always going to be oil in there. More if filter and cap aren't removed.

[feuer]

Originally Posted by TheMidnightNarwhal

I've done mine 2 times as well but I am N54. First time I did not prime it 2nd time I knew about the priming and did it for good measure.

Why the first seal replacement didn't took? Your n54 is relatively new to have to do it twice already.

[TheMidnightNarwhal]

Originally Posted by Pladi

Ur the N54 guy that keeps teasing us prone n55 guys lool

I know that a few well respected members will always refuse that this issue is specific to N55.

Personally I am convinced that early n55s are more prone to this issue for whatever reason.

Hahaha. I also have the feeling it happens to N55 because N54 threads are pretty low but at the same time N54 are sold less I think so.

[TheMidnightNarwhal]

Originally Posted by feuer

Why the first seal replacement didn't took? Your n54 is relatively new to have to do it twice already.

I'm not sure but I would be williing to say it's due to the gasket brand? It was Victor Reinz. It wasn't leaking leaking one year later but it was still "wet", if I swiped my finger under the housing it would come of gunky.

This time I went with the Genuine one that's made in Japan.

[Soden82]

Originally Posted by TheMidnightNarwhal

I'm not sure but I would be williing to say it's due to the gasket brand? It was Victor Reinz. It wasn't leaking leaking one year later but it was still "wet", if I swiped my finger under the housing it would come of gunky.

This time I went with the Genuine one that's made in Japan.

I feel as though brands are hit or miss. Even if they are OE spec ones. There's something about the genuine ones that last longer.

Th OFHG are very sporadic and random to failing I found. I had no problems for 1-2 years and I was very modified when I had my N55. Then I sold it to my friend with 40k miles on the car and it had a leak from the OFHG all of a sudden.