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Thread: BMW F25 X3 N55 Engine - Rod Bearing Failure

  1. #1
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    BMW F25 X3 N55 Engine - Rod Bearing Failure

    Hi Everyone, I am experiencing a used-car buyer's worst nightmare right now. Bought a beautiful 2011 X3 xdrive35i with the N55 motor about 3 months ago from an independent dealer (93k on the odometer, bone stock, no mods). Car was clean, drove great, and CARFAX was OK, but I did notice that it had the ridiculous BMW recommended oil change intervals of 15k. I figured, OK, once I own this, I'll give it the proper 5k changes it needs and we'll be fine. Big Mistake...

    About a month into ownership, I was getting a clattering sort of noise at low RPM, and also on heavy acceleration, but I misread this as some sort of turbo rattle. Also it was intermittent enough to not be too concerned.

    Yesterday, everything changed. The car started making the noise 10 x louder and all the time. This is the noise (someone elses video, but same N55 noise): https://www.youtube.com/watch?v=rNOZviSBe6w

    I am quite certain at this point that this is a rod bearing failure. My indy BMW shop has also confirmed that this is what is going on. Car is not driveable at this point, the knocking is tremendous so I parked it at the shop for now. Sounds like I am going to need a replacement engine though, so I'm pretty devastated.

    Has anyone had any experience with rod bearing failure on an N55? Can it be rebuilt, or is it true that it's just as costly to do that vs. replace with a used engine?

    Car is out of warranty. Not sure if there is any use in contacting BMW NA and pointing to its service history (all done by the book at BMW dealers) as the cause of this premature failure, and seeing if they would help me with the cost of an engine... I saw that the N55 rod bearing part # was updated in 2014, so I'm wondering if this was a known issue.

    Anyone else's experience with this, or any advice is appreciated!!!

  2. #2
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    I've not known of the N55 to have rod bearing failures, nor do I know of any service action regarding this, for that engine.

    I wouldn't expect that BMW will take any goodwill action in your behalf, on a vehicle that's doubled the warranty years and miles, and came from an independent dealer.

    If you're very lucky, and the crankshaft were okay, the cost of doing bearings isn't prohibitive, but judging by your description of the noise, I'd suspect the crankshaft might well be unusable.

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, owner of German Motors of Aberdeen
    BMWCCA 274412
    German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471

  3. #3
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    Oh yeah, that's a rod knock.
    Figure a minimum of bearings and regrinding the crank, if salvageable. If you are seeing flakes in the oil then other parts may have suffered too.
    Opening that overhaul can of worms can get very expensive. If you can lay your hands on a good used engine that might serve you better, at least you have a known cost rather than waiting for an unknown tab from the engine builder.
    At least now you know what a rod knock sounds like and might prevent worse damage next time.
    It sucks, sorry for you.

    If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue

  4. #4
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    I would get a used motor from lkq. I too have not had any rod bearing failures or bottom end failures on my customers car had a few of the shredded belt going the crank seal

  5. #5
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    Thanks for your replies guys. I'm waiting to hear from my shop on whether they think there's any sense in checking the crank/etc for damage, or if it is a safer bet to just get a replacement engine (and not waste labor hours opening up the old one).

    From further reading last night, I was surprised to see several folks with N55 engines pointing to a correlation between recently replacing the Oil Filter Housing Gasket, and then having a rod bearing failure not long after. I think the theory is that either a) if not done properly, the coolant can get into & dilute the oil, or b) if any debris gets into the OFH ports, it can block oil from getting to all parts of the engine. This seems extremely unlikely to me, as I've done 4 other OFHG on other BMW engines, so I was fairly comfortable with the procedure. Anyways, I'm hoping my OFHG replacement didn't trigger this from happening! My money is still on the car not being oil serviced properly in its earlier life, and perhaps one of the previous owners drove it hard before oil temp was adequate. From the service records, the car got its very first oil change at 18k miles, and subsequent changes at 12-15k intervals.

    I appreciate the support and insight into this issue, thanks everyone

  6. #6
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    If you are going to repair the car the old engine needs to come out anyway. It's pretty simple to pop the pan off, wiggle the rods and remove the rod cap.
    I wouldn't think you'd need to pay much for that(I'd be curious enough to do it anyway if I were your mechanic) but I can tell from the sound the crank at the very least will need work and perhaps is junk.
    Good luck.

    If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue

  7. #7
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    If a technician replaces the OFHG on a car that has a heat exchanger at that location (and therefore he replaces the cooler gaskets too), then OF COURSE you replace the oil at the same time. De rigueur.

    That said, that's not why your engine died.

    I think this crankshaft is nitrided, and I don't believe you can fix it anywhere locally, IF it is worn or damaged. I wouldn't even try, IF it's damaged

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, owner of German Motors of Aberdeen
    BMWCCA 274412
    German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471

  8. #8
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    That sucks. I agree that the cause was either some fluke defect in the bearings or lubrication system (unlikely), or that a previous owner ran it really low on oil or had some other issue which caused the bearings to lose lubrication for some period of time. Rod bearings shouldn't just die like that, especially on a street car/SUV that presumably hasn't been thrashed all over.

    Pop the pan and see what the damage looks like. Since you were running for a while with audible symptoms I'm not optimistic, but I suppose there's a small chance that it could just be the bearings with meaningful damage. Sounds like a new N55 is probably in your future.

    And yeah, those oil change intervals are asinine. Oil isn't that expensive. It's just not worth it. I get that 90% of drivers couldn't be bothered about any sort of car maintenance and manufacturers are trying to make it easier for them, but cmon. You can't possibly tell me that over 100-200K miles an engine which had oil changes every 15K will be in better shape than one which had them every 3-5K. It's just treating it as another disposable appliance. That said, I may be biased since I drive a 20 year old car.
    Last edited by TostitoBandito; 08-16-2018 at 02:29 AM.
    1999 M3/2/5 - Titanium Silver - Track/Weekend Toy


  9. #9
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    Quote Originally Posted by bmwdirtracer View Post
    If a technician replaces the OFHG on a car that has a heat exchanger at that location (and therefore he replaces the cooler gaskets too), then OF COURSE you replace the oil at the same time. De rigueur.

    That said, that's not why your engine died.

    I think this crankshaft is nitrided, and I don't believe you can fix it anywhere locally, IF it is worn or damaged. I wouldn't even try, IF it's damaged
    Ah ha! I learned that lesson once. Had one welded up and reground, the journal later broke clean in two. Can be done , just not by anybody and certainly not the guy I used.

    If that engine's first oil change was indeed @ 18k, which is hard to believe,(Not every service gets recorded) then the writing was on the wall from the get go. Surprised it went this long.

    You can't put too much confidence in all these "reports" available on used cars. If you pulled one on my wife's car you'd see several accidents and no maintenance, painting a pretty gloomy picture. The reality is there has never been enough damage to require more than an hour's worth of hammer and dolly work and it's oil is changed every 5k, the trans serviced every 25k and gets most oft neglected services done too.
    Last edited by ross1; 08-16-2018 at 08:45 AM.

    If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue

  10. #10
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    Quote Originally Posted by TostitoBandito View Post
    That sucks. I agree that the cause was either some fluke defect in the bearings or lubrication system (unlikely), or that a previous owner ran it really low on oil or had some other issue which caused the bearings to lose lubrication for some period of time. Rod bearings shouldn't just die like that, especially on a street car/SUV that presumably hasn't been thrashed all over.

    Pop the pan and see what the damage looks like. Since you were running for a while with audible symptoms I'm not optimistic, but I suppose there's a small chance that it could just be the bearings with meaningful damage. Sounds like a new N55 is probably in your future.

    And yeah, those oil change intervals are asinine. Oil isn't that expensive. It's just not worth it. I get that 90% of drivers couldn't be bothered about any sort of car maintenance and manufacturers are trying to make it easier for them, but cmon. You can't possibly tell me that over 100-200K miles an engine which had oil changes every 15K will be in better shape than one which had them every 3-5K. It's just treating it as another disposable appliance. That said, I may be biased since I drive a 20 year old car.
    I think a defective bearing would show up long before this.
    With those oil change intervals( Oh look, that light is on, time for an oil change) I can easily imagine the crankcase being run low more than once. Previous oil starvation would be my guess as the cause.
    Last edited by ross1; 08-16-2018 at 08:51 AM.

    If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue

  11. #11
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