[Bryant]

Hello everyone, so I purchased a used 2016 M235i with 31k miles back on December 4th 2021. I didn’t get the extended warranty because of the low mileage but looking back now I realized that was a huge mistake. On December 29th 2021, my car just went over 34k miles. I was heading home when I hear/feel a loud bang. Immediately after I start hearing a clack coming from the engine bay and also see white smoke in my rear view mirror that is coming from underneath the car. About 20 seconds later it finally shut itself off while I managed to pull over safely on the side of the freeway. I see oil all underneath the car so I already expect that I blew the motor somehow. So finally I managed to get it towed to a shop and they inform me that there is in fact, a hole on the side of the block where cylinder#3 is. So now I’m in need of a new long block pretty much. My turbo and my accessories are still in good shape. My question is, can I get any n55 long block and swap it? Or does it have to be directly from another M235i? Reason is because I see a lot of regular n55s for sale but the m235i engine is more harder to find and more expensive. Thanks and sorry in advance if there is already a thread for this. I couldn’t find any info.

[jb-slow]

You can use a regular n55 long block but it won't have the forged crank that comes in our version.

[XutvJet]

It needs to be 2014+ F series block to make sure you get the better rod and crank bearings. I'd definitely source as M235 block to get the forged crank which most N55s don't have.

[rtl32]

Sorry about the loss, that's a nightmare.

Any idea why you might have had the failure?

As stated above definitely get the M235i block because it's got the forged bits. Similarly you could get the M2 block as well for their pistons as well.

[XutvJet]

My guess is the prior owner knew there was a problem and sold it. The car was likely modded and returned to stock. My guess is a rod bearing was on the way out and finally spun so badly that it cooked the rod and it snapped.

[overcoil]

Originally Posted by XutvJet

My guess is the prior owner knew there was a problem and sold it. The car was likely modded and returned to stock. My guess is a rod bearing was on the way out and finally spun so badly that it cooked the rod and it snapped.

whats the likelihood that too thick an oil could have caused this ?

[Cos270]

Originally Posted by Caravaggio

whats the likelihood that too thick an oil could have caused this ?

How thick are we talking? Would be hard to imagine using oil with too high a viscosity would kill an engine this quick (unless the previous owner abused the car - which seems the most likely).

[XutvJet]

Originally Posted by Caravaggio

whats the likelihood that too thick an oil could have caused this ?

Very doubtful.

What usually leads to rods through blocks on N55s are the following:

1) Hydrolock from ingesting water a column of water through the intake.

2) Heavy engine knock or "super knock" which hammers the piston so hard that it pushes the rod bearing through the oil film layer onto the crank, bearing spins rapidly, heats up massively, cooks rod, and rod fatigues.

3) Doing a number of successive high rpm donuts which sloshes the oil to one side of the pan, oil pickup can't pull enough oil, and the rod bearing spins because there isn't adequate lubrication.

4) Driving on a track with very grippy tires and going through a high G sustained turn which sloshes the oil to one side of the pan, oil pickup can't pull enough oil, and the rod bearing spins because there isn't adequate lubrication.

In most cases of oil starvation, the rod usually doesn't break (just spins the rod bearing), but it isn't totally unheard of.

The OP hasn't said if his M235 was stock or not either. Not saying this is the case of the OP, but people somehow think these N55s can handle way more power than stock. That's true up to a point.

[Bryant]

My M235i was stock, even limited to 130mph. However, the shop said that the turbo looked relatively new so I'm guessing the previous owner had some upgrades on the car. Still currently looking into a replacement M235i engine but there aren't many options. May end up going with a 2014+ F series block because honestly, I'm not going to want to heavily modify it because I don't want to go through another headache... well at least not at the moment.

[Sato]

Hi,
I'm dealing with something similar, only on M135i 2014, but is should be pretty much the same car as M235i. I cannot find spare n55 engine from M235i/M135 (n55b30o0) Can someone confirm that I can use N55 from M2 donor (n55b30t0)? I would like to keep M2 oil pan if possible, maybe turbo if it fits, but other than that, all accessories, ecu and wiring would be from my original engine. Donor car was DCT trans, my is ZF8hp, but since I will be using just "hardware" is doesn't matter right?
Thanks.