N52N engine seized bottom engine block cracks at four cylinders

[kburger]

Hey addicts. Wife’s 128i seized at 140k miles[ATTACH] No warning. 18 year old was driving. But I pulled the codes after that only code was pedal position sensor which was malfunctioning new pedal assembly fixed it. I’m putting up a couple pics here two piece n52n engine block was cracked at four cylinders under the crank. Pics show outside of block marks. What caused this? Long term heat from oil starvation ? Oil changed did have powdery metal particles in it for like 40k miles. But no codes? To take off the torque converter had to use a breaker bar on crank bolt to turn it and line up bolts at the trans. I showed the pics to guys who are good they have no idea what caused this. [ATTACH]

[kburger]

I heard these forums are dead now. That’s a shame. I was on e46 fanatics for a decade. That’s how I got 800k on my 2000 323ci.
Kburger

[spidertri]

Only time I've seen this before was in 4JawChuck 's engine tear down thread. He had the same cracks in his bed plate.

Did you see the cracks prior to removing the bed plate from the block or only after during an inspection and clean up?

[1'M Blue]

Hi

This section is part of the 1M Coupe sub forum

you're better off posting the 128i section to get answers.

[kburger]

Originally Posted by spidertri

Only time I've seen this before was in 4JawChuck 's engine tear down thread. He had the same cracks in his bed plate.

Did you see the cracks prior to removing the bed plate from the block or only after during an inspection and clean up?

Only during inspection and cleaning by the body shop. They could have been there the whole time I didn’t look at those spots. Kinda stupid I should have. Kburger

[spidertri]

Eh, I don't think you should feel bad about not seeing them, who would really think that their bed plate would crack on a motor?

I'm just wondering if the cracks are closed up when it's installed and torqued but when the plate is removed the cracks are able to open up.

Here's the other thread with similar pictures.

https://www.1addicts.com/forums/show....php?t=1993719

[PRTSB1M]

Those cracks are a result of the seizing, not the cause. Oil starvation killed the bearings, just like in the thread spidertri linked to. If 18 year old was hooning the car and the oil was low, sump could've been sucking air instead of oil.

https://f30.bimmerpost.com/forums/sh....php?t=1840025

[spidertri]

kburger Old thread but do you remember which cylinders the bed plate cracks were under?

What did you do to get the car back on the road? New motor or have the original fixed?

[4JawChuck]

Differential expansion rates are what causes the cracks, the inserts are ductile cast iron and the bridge is too light duty for the task.

We can argue forever about Aluminum bearings and how they fail but one thing is for sure they don't belong in any performance engine. I'm a firm believer that had the engine had proper tri metal bearings from the OEM these failures would not occur.

I fabricated steel straps for the bedplate because every one of my caps were cracked,only the magnesium was cracked on mine and the inserts were OK. I think cold weather operation causes the cracks and even simple storage may not prevent it unless kept at room temp its entire life.

Mines running fine, even did the cam ledge last fall to keep it crisp. If I were to do it again I would find a good running low mileage engine and throw some trimetal bearings in it after doing the chain and exhaust cam ledge and reseal with plain sealant on the oil pan and valve cover...mine is tight as a drum with some simple sealant on the gaskets when I put it back together.

[MoerE924u]

I know this is an old thread, but I am having the same issue while rebuilding an N52 for a 2011 BMW 328i XDrive coupe. I actually currently have three crankcase bedplates, and they all have the same cracking (see pics).

From my understanding, the cracks are often due to different thermal expansion rates between the steel bearing inlays and the surrounding magnesium. All three bedplates I have suffer from the same cracking.

Did you or anyone else ever figure out if these cracks are critical? Seems to be a manufacturing defect that affects these engines, especially in places with colder climates (I'm in Minnesota). Did you use the cracked bedplate in your rebuild, and if so, did you have any issues later on?

[4JawChuck]

I reused my bedplate but my ductile inserts were OK. I've seen some where both the magnesium and insert cracked and that would have been a no-go for me.

I custom made steel straps for the inset section of the bedplate and used longer grade 8 Allen head capscrews to replace the torque to yield bolts for additional support and deeper thread in the block which it's already tapped for. If you check out my thread on here I took pictures and posted them for reference, you can find my thread under my username.

Just as bad is the aluminum bearings have a tendency to spin once they grab the crank which damages the bearing registers, mine were salvageable by peening the register and filing it back.

I think cold weather driving makes this issue more likely to happen, my engine is currently running great and I've driven it hard to make sure it can handle the rpm it's redlined for...so far it's been good.

Mixing a ductile steel insert and cast magnesium with such a light casting (there is plenty of room for more meat here) is a manufacturing defect if you ask me...if it happened on an aircraft it would be. The amount of metal that gets into the system destroys the cam ledges, fills the lifters and seizes the valvetronic solenoids too so make sure your do those items at the same time if your rebuilding.

I consider every one of these cars a time bomb waiting to happen unless you upgrade the main and rod bearings to trimetal equivalent.

[MoerE924u]

Originally Posted by 4JawChuck

I reused my bedplate but my ductile inserts were OK. I've seen some where both the magnesium and insert cracked and that would have been a no-go for me.

I custom made steel straps for the inset section of the bedplate and used longer grade 8 Allen head capscrews to replace the torque to yield bolts for additional support and deeper thread in the block which it's already tapped for. If you check out my thread on here I took pictures and posted them for reference, you can find my thread under my username.

Just as bad is the aluminum bearings have a tendency to spin once they grab the crank which damages the bearing registers, mine were salvageable by peening the register and filing it back.

I think cold weather driving makes this issue more likely to happen, my engine is currently running great and I've driven it hard to make sure it can handle the rpm it's redlined for...so far it's been good.

Mixing a ductile steel insert and cast magnesium with such a light casting (there is plenty of room for more meat here) is a manufacturing defect if you ask me...if it happened on an aircraft it would be. The amount of metal that gets into the system destroys the cam ledges, fills the lifters and seizes the valvetronic solenoids too so make sure your do those items at the same time if your rebuilding.

I consider every one of these cars a time bomb waiting to happen unless you upgrade the main and rod bearings to trimetal equivalent.

Thanks for the reply. I have one bedplate with no cracking in the ductile inserts and one with two cracks in the inserts I think, so that's def a no-go. I recently purchased a third bedplate from a seller on eBay who told me there were no cracks in the magnesium, but it turned out he lied to me, so I'm in the process of returning it.

I would be interested in learning how you made your custom steel straps for the magnesium insets if you have the time and photos. That seems like a great idea. I looked at your other post but didn't read where you talked about the steel straps, if you did.

I am actually performing a full rebuild on my N52, and this is my first project on any BMW vehicle, so I am learning as I go. I have two engines that I've fully disassembled, and both had terminal bearing failure, both on the main bearings, similar to the photos you shared.

So far, I had upgraded valve guides inserted, head machined, valve job, and now just trying to locate a new cam cover due to cam bearing failure (groove in cam bearing ledge.

I'm curious what main and rod bearings you used. I am probably going to go with King standard bearings, but do you have a better suggestion? I have two crankshafts, one with minimal wear on the journals that I need to have inspected, so not sure at this point if I can stay with a standard bearing size.

Anyway, thanks for the input. I'm pretty much flying blind here, so any information helps.

[4JawChuck]

Every procedure I performed is included in this post including photos of the straps I had fabricated.

https://www.1addicts.com/forums/show....php?t=1998470

Might want to take into account that having the valves machined will likely change the valve relationship within the valvetronic mechanism. I have not found a procedure on how to accomplish this except for info I found that states the valves should be open 0.010-0.015" when the mechanism is at idle position, even lapping valves removed enough material to change this relationship in my case.

Possibly adjust the eccentric stop position?...I have yet to find out the proper method to make this critical adjustment on the head (may require valve stem length grinding?). It may not be possible hence why BMW only sells complete cylinder head assemblies.

[MoerE924u]

Originally Posted by 4JawChuck

Every procedure I performed is included in this post including photos of the straps I had fabricated.

https://www.1addicts.com/forums/show....php?t=1998470

the valves should be open 0.010-0.015" when the mechanism is at idle position, even lapping valves removed enough material to change this relationship in my case.

Okay, interesting. I had no idea about this. I spent $1,000 on head work with cleaning, resurface, new guides, and valve and seat grinding. What problems did you experience after lapping? It's almost impossible to find a specialist for these engines who understand details like this. Do you think it's safe for me to complete the rebuild after valve and seat grinding considering the loss of material is probably greater than 0.015? Thanks for all the helpful information.

[MoerE924u]

Originally Posted by 4JawChuck

Every procedure I performed is included in this post including photos of the straps I had fabricated.

https://www.1addicts.com/forums/show....php?t=1998470

Might want to take into account that having the valves machined will likely change the valve relationship within the valvetronic mechanism. I have not found a procedure on how to accomplish this except for info I found that states the valves should be open 0.010-0.015" when the mechanism is at idle position, even lapping valves removed enough material to change this relationship in my case.

Possibly adjust the eccentric stop position?...I have yet to find out the proper method to make this critical adjustment on the head (may require valve stem length grinding?). It may not be possible hence why BMW only sells complete cylinder head assemblies.

I'm curious whether MILVs would have any effect on the 0.015 lift requirement. I am planning on installing MILVs in the next few weeks, but now I'm second guessing the head work based on your post. Uggghhh!

[4JawChuck]

Here's the issue as I understand it;

The valvetronic system keeps the intake valve open a small amount during normal lifter pumped up operation. Disturb this by removing valve seat material or getting the valvetronic cam stop adjustment wrong and this relationship is disturbed.

I have yet to find a valvetronic stop adjustment routine anywhere, don't think it was in the TIS since we have all lost access I can't check.

It would seem to me that all that would be required is shimming the stop or machining the length to get this right but where do you start? I would start by fabricating a fixed length lifter so you can mock up the mechanism and figure out the preload on the cam,,,which also controls the slack in the whole valvetronic rocker arm assembly.

Getting this wrong means idle fluctuations and rattling rockers at idle, maybe there is a layman's way of making this adjustment perhaps by shimming the stop and just looking for a certain preload on the rockers?

Wish I knew, testing all this means pulling the rocker cover and playing around with it to see what works as a baseline, I would certainly like a procedure from BMW as they are the ones sending out pre-assembled heads ready to install out of the box.

Some race car engine builder would know how and how much to adjust this as keeping the valve open more might be a tuning aid since the computer tries to adjust idle speed using all methods including the valvetronic eccentric.

We just need to find that guy and get him to chime in (crossing fingers).

[4JawChuck]

Originally Posted by MoerE924u

I'm curious whether MILVs would have any effect on the 0.015 lift requirement. I am planning on installing MILVs in the next few weeks, but now I'm second guessing the head work based on your post. Uggghhh!

Unlikely that would change the adjustment as the stop controls the eccentric start position, MILVs just determine the open position, the ramp built in determines the progression of lift which I have observed is linear.

Should be fine.

[MoerE924u]

Originally Posted by 4JawChuck

Here's the issue as I understand it;

The valvetronic system keeps the intake valve open a small amount during normal lifter pumped up operation. Disturb this by removing valve seat material or getting the valvetronic cam stop adjustment wrong and this relationship is disturbed.

I have yet to find a valvetronic stop adjustment routine anywhere, don't think it was in the TIS since we have all lost access I can't check.

It would seem to me that all that would be required is shimming the stop or machining the length to get this right but where do you start? I would start by fabricating a fixed length lifter so you can mock up the mechanism and figure out the preload on the cam,,,which also controls the slack in the whole valvetronic rocker arm assembly.

Getting this wrong means idle fluctuations and rattling rockers at idle, maybe there is a layman's way of making this adjustment perhaps by shimming the stop and just looking for a certain preload on the rockers?

Wish I knew, testing all this means pulling the rocker cover and playing around with it to see what works as a baseline, I would certainly like a procedure from BMW as they are the ones sending out pre-assembled heads ready to install out of the box.

Some race car engine builder would know how and how much to adjust this as keeping the valve open more might be a tuning aid since the computer tries to adjust idle speed using all methods including the valvetronic eccentric.

We just need to find that guy and get him to chime in (crossing fingers).

This is all good information. Thanks! I think my first option is to contact my machine guy and ask how much material he removed from the valves. Anything beyond that I'll call around to a few BMW tune shops I work with to see what they suggest. I'll post again if or when I find out the fix for this issue.

[kburger]

Originally Posted by spidertri

kburger Old thread but do you remember which cylinders the bed plate cracks were under?

What did you do to get the car back on the road? New motor or have the original fixed?

Talk about a late reply. Sorry! Replaced motor.
Kburger

[kburger]

Holy crap. I’m the OP haven’t looked here in so long because I got no replies for so long initially if you look at my posting dates. Great info everyone glad to see I’m not the only one. Or maybe I should wish I’m the only one!! IMHO slow oil starvation is the cause of this. Mine is N52n motor btw. Maybe figure out how the motors get oil starved and the cracking won’t happen. Manufacturing defect. I agree. Typical. Thanks! Oil starved because of the defect described above. That slowly gets metal into the oil clogging it. Makes perfect sense to me. Gotta love bmw! I guess that’s why valvetronic didn’t become standard on bmw motors. I had it apart. Pretty junky needle bearings in the valvetronic shaft if you ask me. Don’t get me wrong. Valvetronic is a great idea just needs better implementation.
Kburger

[kburger]

I’m changing oil on the 2013 128i now. I have the magnetic drain plug. The engine has like 80,000 miles on it. The drain plug magnet has a nice coating of fine metal shavings on it. This is the replacement N52n engine. I would say the N52n engine is a POS for sure!!! I have 872,000 miles on my 2000 323ci the heads never been pulled. I’d say I’m qualified to judge it. Now I know why there are so few of these cars on the road. This stuff should be covered by lemon laws or class action lawsuit.
Kburger

[4JawChuck]

I purchased a second N52 with a failed rod bearing from a 2011 328i automatic car with under 100000 km on it, spun rod bearing ruined the #6 rod and ate the crank too far to be reused.

However the head was mint, although the #6 piston came close enough to the valves to clean the carbon from the valve reliefs...thankfully no damaged valves...that spun rod bearing thickness is essentially the valve to piston clearance. Interestingly the exhaust cam had spun from its timed position so that's likely what caused it to stop running...must have been knocking like crazy before that happened.

I'm going to port this heads exhaust port the way I wanted to originally and leave the chamber alone to preserve the valve ledge that I blended back in the first engine I did (which is running fine). This chamber side valve seat ledge assists throttle tip in response which would be fine with a race car but on the street it's a little too much, this mod also messed up the idle mixture so it tends to hesitate when driven very slowly.

The exhaust port is where all the gains are to be found in this cylinder head, intake port is formula 1 level excellent so I'm not touching the intake side. Here is a picture of how I am going to port the exhaust side for reference.