Category: N55 Engine Rebuild

BMW N55 Engine Rebuild Project Part 2 – Piston, Crankshaft and Main Bearings Replacement

Posted on by

Hey guys and welcome back to Part 2 of the BMW N55 Engine Rebuild Project. In this video we install a piston, new main bearings, new crankshaft and seal the bedplate. Since the original engine had chunks the size of my fist, yet still somehow ran, I bought another engine on Facebook marketplace and that’s the engine we are working on today. Check out the playlist to see the teardown video and more info on how I got it. If you’d like to see what the original engine actually sounded like despite having chunks of metal and a hole at the bottom, click the links in the description below and before we start, hit that like button like the piston hit the cylinder head on my engine for the YouTube algorithm and to make me feel a little better for spending so much money on bolts and gaskets!


Now, back to this engine that I got for cheap off of Facebook. In the last video, I disassembled it to see if it was worth saving and decided that it’s actually a rebuildable engine. Since then, I have been ordering parts and cleaning all the parts I could clean. I’ve tried a few different degreasers, but ultimately the regular brake cleaner and even the cheaper AutoZone brake cleaner seem to have been working best. I’ve also learned that using a ScotchBrite pad helped get rid of the tougher, built up stuff and smooth out the contracting surfaces. Even though this looks easy and fast on video, it took hours to do, but I WAS being careful not to damage anything as I’m fairly new at this.

Removing and installing a piston

Since this engine spun the bearing on piston 6, I decided it would be best to replace it for a couple of reasons. The most important reason was that there was damage on the connecting rod where the new rod bearing would go, which of course would not last very long even with a new bearing in pl ace. I was also worried that the connecting rod itself could have been slightly bent, internally damaged or no longer perfectly round and since I have 4 perfectly good pistons from the original engine, I decided to swap one in. I picked the best out of the bunch, gave it a good clean and then went to adjust the piston rings.

Now, it’s a little difficult to see this on camera, but the M-Flex ring is made from 3 different parts. Bearing spring being the middle and two steel band rings that go on top and bottom. The idea is to get the M-flex ring and the two steel bands to be 120 degree apart at the opening or separation point. It’s also important to make sure that the contact point is not arranged over what’s called a pin boss or basically avoid the area where the piston is connected to the connecting rod.

Once you have to bottom ring properly adjusted, you need to also adjust the middle and the top ring to be 120 degree from each other. The instructions on this aren’t super clear, but I went with 120 for the 3 parts of the M-flex ring and then again 120 degree separation between the 3 rings.

Now that I had my piston ready to go, I cleaned up the cylinder wall to make sure it was perfectly clean, oiled it and then oiled the piston as well. I don’t have any fancy tools for installing pistons, but honestly, it was much easier than I expected. I used this $13 tool from amazon and it worked perfectly. It’s a little fiddly, so if you do this a lot, spend more money on something more solid, but for me it worked exactly as I need it to. I oiled up the inside of the tool to make sure nothing got scratched and tightened it around the piston. Inserted the tool with the piston into the cylinder and gently pushed it in with my fingers. You do not want to use any tools here or force it in. The new piston is now installed… woohoo!

Installing Crankshaft

Having actually accomplished SOMETHING, I decided it was time for a little bit more cleaning.. I’ve definitely learned that a big part of engine rebuilding is getting rid of all the old muck and gaskets and all kinds of buildup. If I ever do this again, I might get a parts cleaner or maybe a Dremel with a soft pad or something like that. At least getting it to look new again DOES make you feel like some progress is being done, so that’s a plus.

Now that I felt better about how it looked, I removed the connecting rod bolts and the connecting rod bearing caps on the big end. It’s VERY important that these rod bearing caps do not get mixed up and go to the correct connecting rod when reused or you’ll have another knocking engine very soon. I marked them and put aside until they are needed again when we replace the rod bearings in the next video. The bolts will also be used before the final install for testing, so I’m keeping them for now. Subscribe to the channel so you don’t miss that video! Now that the crankshaft is not held in by anything, it can be simply removed from the engine. Do be careful as it weighs about 50 pounds and you don’t want to drop that on your foot.

I wanted to show you the difference between a good crankshaft and onethat has been abused. Let’s compare the crankshaft from the original engine to the one I’m installing shortly. You can see how much shinier and smoother journals are on the good part. Of course, the old one is not going to waste, it can be resurfaced and used again with oversized bearings.

Back at the engine, I removed all of the old crankshaft bearings, cleaned the area with some ScotchBrite and removed the residue with brake cleaner and a lint free paper towel. We are now ready to install the new stuff!

Installing Main Bearings

WHY am I going with aftermarket main bearings? Well, that’s a very good question with a few answers. First, these seem to have a better reputation with people that have rebuilt their N54 and N55 engines. Second, these King bearings have an improved crankshaft finish for reducing microscopic ferrite peaks if your crankshaft isn’t perfect and since I’m not installing a brand new one, it isn’t perfect. They also have improved oil clearances which should reduce wear on the engine and increase its life. Other than all of those reason, the price was also a factor as these much less expensive compared to OEM.

Installing these is actually fairly simple, put the grooved side in first, squeeze the bearing just a little and push it down with your fingers. They pop in and seat themselves when done correctly. At least they did in my case. The set with a little oil hole goes on the engine block and the solid ones are installed on the bedplate. Of course, I cleaned all surfaces to make sure there was nothing there before installing.

Now that everything is ready, we can temporarily install the crankshaft so that we can check the crankshaft bearing clearance. If it didn’t go in perfectly on the first try, don’t spin it, lift it out a little bit and put it back down where it’s not in the way of anything.

To make sure the bearings have seated correctly and are not over or undersized, it’s important to check the crankshaft bearing radial clearance. For this BMW recommends using plastigauge. I have a full video on how to use plastigauge if you’d like to see the entire process. The basic process is to cut a piece of plastigauge the width of the journal, place it on top of each journal you’d like to test and then install the bedplate back on the engine block.

We then follow the correct sequence to install the bolts and torque them to spec! I left mine for a couple of minutes and then removed the bolts and the bedplate.

Now that I’m confident with the fitment of my new crankshaft, it is time to do the final assembly. Of course, I have cleaned all of the areas again and removed the plastigauge from the crankshaft as well as the bed plate. With all the surfaces clean, I then installed some assembly lube as this will be the only oil between the journals and the bearings when the engine runs for the first time. After the oil pressure is build up, regular oil will go in through the holes in the bearings and lubricate, but we have to protect the engine for those first few rotations. I put some assembly lube on the bedplate bearings as well and even rub a little on the journals directly. This stuff isn’t going to hurt anything and it still much better to the surfaces compared to regular oil.

Since there is no gasket between the bedplate and the engine block, it has to be sealed with a special sealant. The one I got is recommended by BMW and is specified in the service manual. I applied a good bead into the groove as specified.

I really hope you enjoyed this video or at the very least learned something new. If you enjoy this type of content or just like cars, check out the rest of the channel for many more car related videos. Most aren’t nearly as technical. Thank you so much for watching and I’ll see you in part 3 where we install the rod bearings.

BMW N55 Engine Rebuild Project Part 1 – I Bought A Broken BMW N55

Posted on by

Hey guys and welcome back to another video on the SimpleCarGuy channel. It has been a few months since I have started working on the e92 project and I know I haven’t posted an update in a long while. So, in this video, I will go over why it took so long, what’s happening now and the plan for the future. After taking the engine out of the car and tearing it down to see what it looked like, I found that it was not rebuildable at all and I had to find another engine. Unfortunately, that’s where I ran into some issues. At the time of buying the car, a BMW N55 engine could have been had for under $3000 with less than 100,000 miles minus the turbo and some accessories, which I would gladly pay. However, whether it was due to pandemic or winter being right around the corner, the engines just disappeared from the market and the pickings were slim. The best engine I could find was over $4000 with 135,000 miles out of a wracked car with no warranty or guarantee. Now, I could have risked it and went for it, but it felt like such a step back. I waited and waited and nothing came on the market.

Then one day I was on Facebook market looking for random car stuff as I normally do and I searched for a BMW N55. To my surprise, there was one for sale and it was only 5 miles away from me. What was more surprising was the asking price – $350. I figured, for $350, it can’t hurt to at least go look at it. I had a good look at it and it was a clear case of spun rod bearing. I realized that this engine in a rebuildable condition, so I pulled a trigger on it and bought another knocking BMW N55 engine. Of course, it’s not in a perfect condition by any stretch of imagination, but it’s decent enough to attempt rebuilding.

I brought the engine home, put it on a stand and started taking it apart to inspect it closer. So, how good of shape is it really in? Well, let’s find out!

Even though the guy that sold me the engine swore that the only damage to the engine is the spun rod bearing, I have seen what a spun rod bearing can do, so I had my doubts. My biggest worry was damage to the cylinder head and the cylinder walls which would make the engine not worth rebuilding. I used a small camera to go through the sparkplug hole and what I saw scared me a little bit. It looked like it was all cracked and black and not like it’s supposed to look. However, once I removed the cylinder head, I was pleasantly surprised, everything was intact and in good enough shape! Who would have thought!? This game me the go ahead to start ordering parts and proceed with the teardown.

I didn’t include the tear down footage on this engine up until this point as it’s pretty much exactly the same as I did on the original engine. Check out those videos for detail on how I got to this state of the engine.

While I do some research and wait on parts to start arriving, I’m continuing to take apart the bottom end. To remove the bed plate, I had to first remove the main crankshaft bolt, which turned out to be a not-so-easy task once the engine is on an engine stand. I ended up using a wrench to hold it in place and a very long pipe to break it lose. Now that the main bolt was out, I was able to remove the crank hub which then allowed me to remove the sprockets and the chains. A few screws and bolts later, the oil pump was ready to be removed as well.

The last step in disassembly was to remove the bed plate bolts in the correct sequences as well as all of the outside aluminum bolts. It’s mandatory to replace all aluminum bolts when re-assembling the engine, so lots of ordering a head of me. I then removed the bed plate from the engine block to expose access to the crankshaft. This is why I did so much work disassembling this engine. It’s to replace this big ol chunk of metal. I won’t be releasing those rod bolts until I’m ready to put the new one in as I’m afraid of accidentally pushing the piston out and it falling on the floor.

At this point I’m pretty much done with the disassembly of the engine and it’s rebuild time! I have ordered most of the parts I will need to get started, but first I will have to clean all of the parts I will re-use and set up a better work space for myself. The plan after is to replace one of the pistons, put all new main bearings in and replace the crankshaft. Put the bed plate back on, seal it with the correct sealant, install gaskets and seals back in and reassemble the rest of the bottom end. This of course will be in another video, so don’t forget to subscribe to follow this rebuild project.

BMW N55 335i Cylinder Head Removal & Engine Teardown

Posted on by

In the previous engine teardown video, I removed the oil pan and oil pump to investigate why this BMW n55 engine had such a horrible knock. After seeing the spun bearing and the destruction it had caused, I decided to continue with the engine disassembly and take off the cylinder head off. There are quite a few steps to do this, such as removing the valve cover, the injectors, the fuel lines and all of the wiring. I also had to get a timing tool to hold the VANOS system in place to remove the timing chain. After all of this work was done, I was finally able to remove the cylinder head and inspect the valves and the mating surfaces.

Taking apart a blown BMW N55 Engine

Posted on by

After spending the last few weeks removing the N55 engine from my BMW 335i, I’m finally taking it apart so that we can see what has been causing that horrendous knock and how much will my wallet be hurting after this project. Check out the playlist on this car to get caught up if you’re new here! Let’s get to it!

BMW N55 Engine Inspection at 85000 Miles

Posted on by

In my previous video I took the engine out of my BMW 335i e92 and before I take it apart, I wanted to point out some of the issues and see what kind of shape the engine is after 85000 miles in midwest. This video isn’t supposed to be in depth or anything like that, but I just wanted to highlight a few common problems on the N55 and issues specific to this engine.

How To Remove BMW N55 Engine from BMW 335i

Posted on by

Hey Guys and welcome back to another video and this is a long one! In this video I will be removing the BMW N55 engine out of my BMW 335i e92 coupe. I recommend checking out my previous videos on this car as they explain a lot of what is going on and why I’m removing the engine. I do skip over some of the parts, but most of the big stuff is included. I hope you enjoy and give this video a like!

As I’m not a BMW mechanic and I do this just for fun, so I ran into a few issues along the way. Some of these really were easy to solve, but required tools I didn’t have and some required some thinking even when I did have the right tools. I’ve learned a lot along the way and I think this is one of the best ways to get very familiar with your project car.

I started this project with some safety in mind as I’d be crawling underneath the car, so the very first thing I did was disconnect the battery that way I don’t chance it with the ECU, catch something on fire or short something out in general. After putting the cars on jack stands, I got busy with removing the interior air filter and both lower and upper section of housing that hold it in place.  I then removed the trailing links with just a couple of bolts and proceeded to remove the intake filter housing, the cowl panel cover and the clean air pipe. Once all of these items were removed, I had easy access to the intake manifold that’s held in by 7 nuts and a screw. Before I pulled it out, I made sure to unplug all of the connectors on the ECU and move the wires out of the way. Then it just pulls out. Don’t forget to disconnect the vacuum line at the bottom as well so it doesn’t break on you! The car has been treating me nicely thus far and I was excited to keep wrenching. I had music playing in the background and it was just me and the car.

My next mission was to drain it of as many liquids as possible. I drained the oil off camera and got to work on the coolant system. To get better access, I removed the fan cowl with just one bolt and go to draining the coolant from the bottom hose and once it was all drained, I took the expansion tank off as well. As I kept removing parts from the engine, I would disconnect and remove coolant lines along the way.

So far it has been basic mechanical wrenching and I’ve been enjoying it with no problems in sight!

Now that I have had plenty of space, I removed the serpentine belt which allowed me to remove the alternator as well as loosen the AC compressor. At the same time I removed the oil pipes making sure to catch any access oil spills.

At this point things have still been going pretty smooth, so I decided to tackle one of the harder parts of the engine removal. The removal of the axles or the output shafts, if your car is rear wheel drive, consider yourself lucky since you won’t have to deal with this royal pain in the butt! Now, undoing the bolts on track rod end, the wishbone, the trailing link and the anti-roll bar was a piece of cake compared to trying to take knock out the shaft out of the differential. Don’t be like me and try to follow BMW’s recommendation and just use a screw driver like I do here to pop them out. It’s definitely worth the cost of a seal.

Next I decided to tackle the removal of the catalytic converter. It looked very easy in the manual, so I figured it’d be out in an hour or so. At surprise to no one, I ran into some issues. The biggest issues I had here was that I could not separate the exhaust from the catalytic converter. I tried taking the bolts off with a socket, with some heat and plenty of WD-20, but at the end I had to cut them off with a grinder and break off the ones I couldn’t reach using an air hammer gun to separate the two pieces. I’m glad I’m not an exhaust guy in Midwest. What a nightmare that was. I then spent the next 20 minutes getting to the bolts on the engine support arm and the engine mount was out with the support arm. I was in the clear! Or so I thought. After removing the clamp, the cat was supposed to just come out.. but it never did. I eventually game up on it and removed the engine leaving it in place.

With all that extra space around the transmissions I was able to take the rest of the bolts out holding it to the engine. I can’t say they were easy, but using the CV joint extension and the short sockets. I was able to get all of them out in no time at all. I thought the engine is now ready to be separated from the transmission… but WAIT THERE WAS MORE!

After struggling for a bit, I had to do some research and I found out that since this is an automatic, the torque converter would be too large to come out with the transmission EVEN if it did separate which mine just wouldn’t. I decided to remove the 6 converter bolts and while I was under the car removing the bolts, I saw that propeller shaft was still attached to the differential, so I removed the 4 bolts and dropped the shaft down. Glad I caught that one before too much damage was done!

I then used a pry-bar to put some tension between the engine and the bell-housing hoping it would make it easier to separate.  Nothing was stopping me now! I was on a mission!