[carguy138]

Originally Posted by Will_460cs

Disconnect the injectors individually and I would do the coil packs too - that is from bmw technical docs and is the safe way to do it as it the only way to guarantee no firing

Or follow those lines to the plug on the DME and unplug that one. Does the same thing except you are removing one plug instead of 12.

On the E90 N55 it's the farthest plug to the right (closest to firewall) if you are looking from the top.

NOTE: it's a slide lock. You have to pull the tab toward you to release this plug from the DME.

[wheela]

Originally Posted by Will_460cs

Full bmw service history

Thanks!

[Dynamics99]

Originally Posted by Will_460cs

Disconnect the injectors individually and I would do the coil packs too - that is from BMW technical docs and is the safe way to do it as it is the only way to guarantee no firing

You can either disconnect the injectors or pull the cable that inserts into the positive battery terminal. But either way, I would ensure that the rail pressure is bled first.

[scotthilly]

Ugh, having a similar internal debate.

83k 2011 N55, stock but with MPPK. Charge pipe cracked and broke throttle body, resulting in $1600 repair.

Now thinking about what to do - and rod bearing seems smart. OFHG and oil pan housing gasket were both replaced in 2018, 40k miles ago.

Considering preventative rod bearing, but I know it’s easy to do the two gaskets at the same time. Should I do all 3? Or good with none?

Any insights appreciated.

[Dynamics99]

Originally Posted by scotthilly

Ugh, having a similar internal debate.

83k 2011 N55, stock but with MPPK. Charge pipe cracked and broke throttle body, resulting in $1600 repair.

Now thinking about what to do - and rod bearing seems smart. OFHG and oil pan housing gasket were both replaced in 2018, 40k miles ago.

Considering preventative rod bearing, but I know it’s easy to do the two gaskets at the same time. Should I do all 3? Or good with none?

Any insights appreciated.

I would do them.

[yupetc]

Piece of advice for anyone who's going down the dungen to do your rod bearings: Do replace the rod bolts with ARP rod bolts. ARP bolts are much stronger, they provide consistent clamping force, and can be re-used after some simple checks and verifications.

And for the rod bearings, King and ACL bearings are both great. I'd also go for upgrades on these bearings if they are available. Below are my recommended rod bearings to look for:

1) King CR 222GPC (I currently use these, after 20k miles pull out and inspect, not even a scratch nor any wear.) These bearings have coated babbitt. Definitely high performance.

2) ACL 681584H Get these from Race Engineering because they sent these in for Calico coating. I use their Calico coated main bearings and it's been a beast ever since.

Having coated rod bearings will get you a slightly tighter bearing gap without eating into the friction surfaces. And the N55 OEM bearings are simple 2-layer bearings. These King and ACL bearings that I recommend will get you coated treatment which are very similar to the B48 and B58's "iROX" coatings.

[Dynamics99]

It's been a while. I pulled the motor out and disassembled it. Waiting on parts now and I need to get the crankshaft reground since there is a single score mark on the cylinder 1-rod journal.

The connecting rod for cylinder 1 was bent and mangled but the piston did a good job so it's still useable. The oil squirter was flattened and there is a gouge near the oil squirter.

I will upload a picture of the score mark.

[yupetc]

You'll need to work with larger bearings after the grind. In this case, I'd buy the bearings first, bring it in with the crank and rods and have the machinist set your rod bearing gap on the grind.

[wheela]

With a re-grind, do they re-grind all 6 journals to try to keep it balanced, or is grinding just 1 journal not enough to matter? Is there more or less risk grinding all 6 vs. just the damaged journal?

[Dynamics99]

Originally Posted by wheela

With a re-grind, do they re-grind all 6 journals to try to keep it balanced, or is grinding just 1 journal not enough to matter? Is there more or less risk in grinding all 6 vs. just the damaged journal?

I'm not sure. I would like to regrind only the affected journal. Matter of fact the entire journal for cylinder 1 is not scored. only two areas. The bearing didn't even get time to heat up to temp. it just spits it out.

Wondering if I can get away with regrinding only the one journal and running oversized bearings on that.

What's the consensus? In the meantime, I ordered a used short block which looks like in good condition. I didn't take the head apart so I'm just gonna clean the surface as best as I can.

[Will_460cs]

I have no direct experience, but my understanding is that the process is to do all journals so they are the same size.

[yupetc]

When you bring the crank to the engine shop, they'll usually run a few gauges to check the crank for bends first. If that's passed and your crank spins freely and true to concentricity, then they'll look at your journal.

If it's just a small score on the journal and not too deep, they can just polish that up a little bit, and they'll have you noted to purchase a small size up bearing (just for that journal), this is usually 0.001" size up. And localized repair on that singular journal is all it takes.

If they determined that the scoring is too deep and must go through a full grind to the next size, then you'll be asked to purchase the 0.025" size up set of bearings. And in this case, they will grind all 6 journals, so you'll be buying 6 bearings. Also if this is being done, the machinist will etch a mark legibly on the crank's counter-balance

In ACL bearing nomenclature, as an example, you'll see xxxxxxx-STD for standard bearing size, then xxxxxxx-STD-HX001 or -H025. I'm just vaguely recalling these deets from my head, so go check and confirm on your own if you're having to go either of these routes. Good luck.

The way I usually do this is I'd bring the crank, the short block, and the rods/pistons to the shop altogether because whatever size bearing they'd have me purchase, I usually have to send in the rod bearings in before they begin work, that way when they grind the crank journals, they can always check and match as they grind and approach the target tolerance. They may try to upsell you to do a crankshaft or full assembly balance; I usually skip those, but it's up to you.

[Dynamics99]

Originally Posted by yupetc

When you bring the crank to the engine shop, they'll usually run a few gauges to check the crank for bends first. If that's passed and your crank spins freely and true to concentricity, then they'll look at your journal.

If it's just a small score on the journal and not too deep, they can just polish that up a little bit, and they'll have you noted to purchase a small size up bearing (just for that journal), this is usually 0.001" size up. And localized repair on that singular journal is all it takes.

If they determined that the scoring is too deep and must go through a full grind to the next size, then you'll be asked to purchase the 0.025" size up set of bearings. And in this case, they will grind all 6 journals, so you'll be buying 6 bearings. Also if this is being done, the machinist will etch a mark legibly on the crank's counter-balance



In ACL bearing nomenclature, as an example, you'll see xxxxxxx-STD for standard bearing size, then xxxxxxx-STD-HX001 or -H025. I'm just vaguely recalling these deets from my head, so go check and confirm on your own if you're having to go either of these routes. Good luck.

The way I usually do this is I'd bring the crank, the short block, and the rods/pistons to the shop altogether because whatever size bearing they'd have me purchase, I usually have to send in the rod bearings in before they begin work, that way when they grind the crank journals, they can always check and match as they grind and approach the target tolerance. They may try to upsell you to do a crankshaft or full assembly balance; I usually skip those, but it's up to you.

Quite hard to find one in Philadelphia right now. Once I find one I will check if I can bring over the block. I have ordered another short block since the squirter got flattened and there is a gouge next to the squirter that pokes out into the cylinder wall. It may not hit it but I didn't want to take a chance. Will probably have to go the next size up for bearings. Piston 1 is still good to go. Will need new rings on all pistons.

Here is the score image:

[yupetc]

Put some viscous assembly oil on it to prevent it from rusting. Keep it this way until you get it to a engine shop and let them decide. It's kind of hard to tell from the picture, but it almost doesn't look that bad unless you can attest that the scoring is more than polishing can do. Anyway, keep all the journals lubricated with a good film of oil or some assembly lube until the machinist can access it. Let them decide what to do with it.

Just FYI, the first time I took my N55 crank to the machine shop, asked them to grind out 0.025" due to one bad scoring on #6 journal, they did the deed, but when I took it back to my garage to put together, I couldn't size my rod bearing even with a proper 0.025" oversize I just couldn't close the gap because the machine shop went slightly overboard with the grind. So I ended up buying a brand new OEM crank because what's available for a used crank on eBay at the time just couldn't justify the condition versus the cost. This is why I say it's best to bring at least the rods and the rod bearings to the shop and have them grind and match the bearing tolerance you need to achieve. OEM tolerances are VERY tight, but that's expected due to the thermo characteristics of the OEM journal/rod/bearing combination. If you use an aftermarket rod or bearing, or both, then be ready to accept bigger bearing clearance. There will be some homework and learning curve to absorb, be ready mentally. Last thing you want happening is you arriving at the engine shop and don't know all the lingo and can't really converse with the folks there. Most shops don't deal with BMW cranks, so we have a chip on our shoulder walking into most shops in the states. They are more accustomed to those old blocks with wide-open clearances. Throwing a BMW book kept clearance on their table may earn you some cold stare down from some of the old stubborn folks there.

[yupetc]

Also worth mentioning, I just hauled my N55 motor out of the X5 recently. Already took it apart to the short block right now. Just this week, I took my forged pistons/rods off to inspect the rod bearing after 20k miles of abuse. All are good. And I'm on my way buttoning everything back together right now. So as you progress on your end, I'll keep my eye open on this thread in case you post more questions/issues along your build, and I can try to help answer your questions while I'm still fresh with the work. I haven't been doing too many N55 rebuilds since COVID, so I can attest sometimes you'll second guess a few if you're new to this motor's build procedure.

[Dynamics99]

Dropped it off at the shop. I had oiled it up and made sure there is enough paper wrap to keep it from sitting on itself.

Talked to the owner. He is going to polish it as it barely catches on the fingernail. Going to bring my connecting rods with the STD bearings on Monday. He wants to measure the clearance and let me know. Quite a good guy from the conversation.

Praying all it needs is a polish haha.

[Dynamics99]

Originally Posted by yupetc

Also worth mentioning, I just hauled my N55 motor out of the X5 recently. Already took it apart to the short block right now. Just this week, I took my forged pistons/rods off to inspect the rod bearing after 20k miles of abuse. All are good. And I'm on my way buttoning everything back together right now. So as you progress on your end, I'll keep my eye open on this thread in case you post more questions/issues along your build, and I can try to help answer your questions while I'm still fresh with the work. I haven't been doing too many N55 rebuilds since COVID, so I can attest sometimes you'll second guess a few if you're new to this motor's build procedure.

Im new to this platform. I have a Z4 3.0i with the M54B30 motor and it just goes and goes even after sitting for months.

With the N55 it's my first ever motor teardown. I wanted to save money by doing it myself and only taking it to the machine shop for things I cannot do.

So far for seals I need:
Front and Rear main seal,
Oil Pan Gasket (Probably use the current one since I just replaced it? I can exchange with FCP Euro if needed),
The lower crankcase sealant,
Flange sealant,
Head gasket

Let me know if I am missing anything.

For bolts:
Oil Pump,
Pickup tube,
Lower crankcase,
crankshaft bolts,
head bolts,
oil pan bolts,
crank pulley bolts,
crankshaft 22mm bolt.


Timing:
Timing chain,
guide,
sprocket (is there a way to check if the sprockets are in good condition)?

As for the rods do I have to get a whole new set or get a low mileage used one and match it to weight of the current ones? The piston is in good shape for cylinder 1. No cracks or dents. The rod needs to be replaced.

When I initially replaced the bearings I went with KING bearings STD size. I measured the clearance and they came out to be 0.038mm for all 6 rods.

I know KING offers oversize for both main and rod bearings.

[yupetc]

Originally Posted by Dynamics99

Dropped it off at the shop. I had oiled it up and made sure there is enough paper wrap to keep it from sitting on itself.

Talked to the owner. He is going to polish it as it barely catches on the fingernail. Going to bring my connecting rods with the STD bearings on Monday. He wants to measure the clearance and let me know. Quite a good guy from the conversation.

Praying all it needs is a polish haha.

Looks like you're in good hands. That's great!

[yupetc]

Originally Posted by Dynamics99

Im new to this platform. I have a Z4 3.0i with the M54B30 motor and it just goes and goes even after sitting for months.

With the N55 it's my first ever motor teardown. I wanted to save money by doing it myself and only taking it to the machine shop for things I cannot do.

So far for seals I need:
Front and Rear main seal,
Oil Pan Gasket (Probably use the current one since I just replaced it? I can exchange with FCP Euro if needed),
The lower crankcase sealant,
Flange sealant,
Head gasket

Let me know if I am missing anything.

For bolts:
Oil Pump,
Pickup tube,
Lower crankcase,
crankshaft bolts,
head bolts,
oil pan bolts,
crank pulley bolts,
crankshaft 22mm bolt.


Timing:
Timing chain,
guide,
sprocket (is there a way to check if the sprockets are in good condition)?

As for the rods do I have to get a whole new set or get a low mileage used one and match it to weight of the current ones? The piston is in good shape for cylinder 1. No cracks or dents. The rod needs to be replaced.

When I initially replaced the bearings I went with KING bearings STD size. I measured the clearance and they came out to be 0.038mm for all 6 rods.

I know KING offers oversize for both main and rod bearings.

Your list seems just about right to me. I think you're missing the oil pump chains and the oil pump tensioner. On the oil pump chain guide, check the plastic rails where the chain passes. If you see some deep grooves, be ready to get a new one. Make sure to go OEM. I've installed a no name one from an eBay purchase. Those are so cheap they are a dime a dozen, but in less than 20k miles of use, tensioner plunger got stuck, I ended up with chain slap and now I'm dealing with the aftermath. There are two types of tensioner for the oil pump chain, so if you have a plunger, you'll need to break that small black rubber access cap to see it. To get the oil pump chain guide out, you'll need to break open the black rubber access cap right under the pulley tensioner. These will need new ones going back in.

On timing chain, be sure to remove the bolts for the chain guide. If you didn't remove the vacuum pump then you've one less gasket to replace. On crank hub, you'll need to replace the friction pad for each of the mating surface between the sprocket gears (timing and oil pump driver sprockets is what I'm referring to). To inspect sprocket gears, you'll just have to visually take a look. If there's no signs of bad wear or witness marks of tooth skippage, you'll be able to use them again.

For rods, you can just get a low mileage one and get by. But you'll need to run a wrist pin clearance check and rod bearing crush clearance check too. OEM rods are pretty uniform in weight. This is also where the engine shop can be inquired to see if a crankshaft balance with rods and pistons is a service they can perform too. I highly doubt you'll get balance issues by using an OEM rod, though.

If you're comfortable with King bearings, stay course. The tolerances you listed are good. but make sure to plastigauge check them 2-3 times again on your build back. Tolerances can be found on newTIS website. Just register an account and find the vehicle you're on, look into the engine's different components and you can find spec sheets there.

[Dynamics99]

Originally Posted by yupetc

Your list seems just about right to me. I think you're missing the oil pump chains and the oil pump tensioner. On the oil pump chain guide, check the plastic rails where the chain passes. If you see some deep grooves, be ready to get a new one. Make sure to go OEM. I've installed a no name one from an eBay purchase. Those are so cheap they are a dime a dozen, but in less than 20k miles of use, tensioner plunger got stuck, I ended up with chain slap and now I'm dealing with the aftermath. There are two types of tensioner for the oil pump chain, so if you have a plunger, you'll need to break that small black rubber access cap to see it. To get the oil pump chain guide out, you'll need to break open the black rubber access cap right under the pulley tensioner. These will need new ones going back in.

On timing chain, be sure to remove the bolts for the chain guide. If you didn't remove the vacuum pump then you've one less gasket to replace. On crank hub, you'll need to replace the friction pad for each of the mating surface between the sprocket gears (timing and oil pump driver sprockets is what I'm referring to). To inspect sprocket gears, you'll just have to visually take a look. If there's no signs of bad wear or witness marks of tooth skippage, you'll be able to use them again.

For rods, you can just get a low mileage one and get by. But you'll need to run a wrist pin clearance check and rod bearing crush clearance check too. OEM rods are pretty uniform in weight. This is also where the engine shop can be inquired to see if a crankshaft balance with rods and pistons is a service they can perform too. I highly doubt you'll get balance issues by using an OEM rod, though.

If you're comfortable with King bearings, stay the course. The tolerances you listed are good. but make sure to plastic gauge check them 2-3 times again on your build back. Tolerances can be found on the new TIS website. Just register an account and find the vehicle you're on, look into the engine's different components and you can find spec sheets there.

Will be replacing the plastic timing guides, chains, and sprockets. The oil pump guide is fine but the plastic piece to hold the small sprocket broke. This is an image of one of the member's posts but he highlights that part.



Think I will go with forged rods depending on the price of the set. I see online where N54 can bend their rods and I know N55B30A has cast rods.

I have ISTA so I can bring up the clearance spec. I appreciate your knowledge. Quite difficult to get some info on the forums these days as I don't see many posts about N55 rebuilds but I see them spin bearings. Maybe I will just document the entire process here for others.

This time I'm gonna torque it right. It shouldn't shoot through the oil pan .

[yupetc]

Originally Posted by Dynamics99

Will be replacing the plastic timing guides, chains, and sprockets. The oil pump guide is fine but the plastic piece to hold the small sprocket broke. This is an image of one of the member's posts but he highlights that part.

Attachment 3229260

Think I will go with forged rods depending on the price of the set. I see online where N54 can bend their rods and I know N55B30A has cast rods.

I have ISTA so I can bring up the clearance spec. I appreciate your knowledge. Quite difficult to get some info on the forums these days as I don't see many posts about N55 rebuilds but I see them spin bearings. Maybe I will just document the entire process here for others.

This time I'm gonna torque it right. It shouldn't shoot through the oil pan .

Yes, same here, I have documented everything in my little engine build notebook. But I probably could do a better job and documenting it up here for everyone to share. But getting the whole thing sorted and typed up can be a time-consuming task. So I haven't the courage to brave the task. If you do so, it's definitely a big contribution for the community.

On that picture you posted, it looks like you have the spring type chain tensioner. It's an earlier iteration of the N55 motor. So yeah, that little circled holding tab is necessary to help support and pre-load the chain and sprockets altogether to put onto the block. As long as those plastic gliders for the chain to rest on do not have deep gouged grooves, you're free to re-use those again. The oil pan gasket I would replace with new despite you just recently had it replaced. My reasoning is because you've had it installed once, it's crushed-in already. I do not know if re-using it will get you a good full seal, but risk is there. And while you have everything out, it's much easier to do, so you might as well.

Forged rods I use for my build is Manley rods. I didn't remember to record the weights, but Manley rods are made of steel, much heavier than the stock rods. So you may see a little bit of rev lag, associated with turbo lag. But if that doesn't ruin it for you, I'd say go for it. These rods are extremely strong.
(Note: I don't know if lags are there because right after I had the forged build, I went ahead and MHD tuned it, so I wasn't able to do a before and after "feel" comparison. But my focus is on a robust build, so even if that lag exists, it doesn't matter to me.)

ISTA is also a great way to pull out the service instructions. I totally forgot that feature. I run ISTA on a 13" laptop, so with these little screens, I've never refer to ISTA for the repair instructions. I've always pull up newTIS on my big screen TV in the garage. And for the rods, yeah, definitely get some ARP 2000 rod bolts. If you buy Manley rods, the rod bolts are ARP included IIRC. ARP rods bolts are simple to torque, 55 ft-lbs (wet from 5w-30 oil soak). I torqued mine to 60, considering inaccuracies of my torque wrench.

[Dynamics99]

Dropped the pistons off Monday at the shop. The owner said crankshaft will be ready Friday and cleareances was checked for me.

Hopefully everything comes back normal and does not need a regrind.