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Discussion Starter #1 (Edited)
Sorry for the images with the white section but I have to do it or they appear the wrong way up. The videos aren't displaying correctly, I think they need admin verification and even then I think there might be a limit on how many I can link for some reason?

As promised, this is my how to guide to fix the carbon build up problems with the N54 engine, which is something not well documented in the UK. The images in this guide will be of my work on my 135i unless stated otherwise. There is also a lot of false information about fixing these problems such as simply slapping on a catch can and you’re done. Meanwhile the other side pf the PCV system is unfiltered and you haven’t cleaned your valves. This leads to garages giving catch cans a bad rep I suspect. It’s worth mentioning I have yet to do enough miles to test weather or not this completely eliminates the need to clean you intake valves however judging by the amount of oil one of my cans caught in just 247 miles it will certainly help a hell of a lot. It also completely eliminated white smoke from my exhaust (EDIT: I did get some recently in very hot weather in stop start traffic in town, probably turbo seals). However, I still have minor oil consumption which is probably the turbo seals which will likely fail on my watch.

This guide is broken down into 5 sections.
• Principle
• Items list
• Other guides
• Preparation
• Installation
6 steps:
1. Stripping the engine
2. Plugging the head ports
3. Rebuilding the top of the head
4. Cleaning the intake valves and other intake parts
5. Installing the PCV kit, cans and drain kits
6. Testing​

The problem and the principle

See my previous post (here It contains detail on the problem of carbon build up, the solutions and there are videos with explanations to help you understand.

Items list

I have listed all the components needed to complete the different levels of this modification including the modification I have installed myself which is the most comprehensive. I will also list what I consider to be specialist tools for the job. If you have access to a well-equipped workshop you may already have these tools as they are not truly “specialist” but are things your average car guy probably won’t have.
you have three options:
This is the official post from RBturbo about the different kits and provides other useful links.

Option 1: Just the modified valve
Difficulty level 2/10
For this all you need is a modified RB valve which you can simply swap with the OEM one. You can get this from RBturbo or MLperformance who are an excellent BMW aftermarket supplier and authorised RBturbo UK supplier.
RB valve
MLperformance (MLP)
Follow my guide to up to step 2 then skip to step 5’s section about the RB valve, or watch this guide.
Youtube guide:

Option 2: The modified valve, throttle body adapter and two catch cans

Difficulty 4/10
For this you will need one of the external kits from RBturbo or MLperformance which includes the valve and throttle body adapter. From what I can tell all the kits include the grub screws probably because the cost is negligible. But you can just discard them.
Two catch cans, one mishimoto and one BMS or you can use whatever cans you like but make sure the high flow one is designed for that. You can add drain offs to them to if you like.
External PCV kit
RBturbo -
BMS catch can - or for 535i
Mishimoto compact catch can -
Custom catch can bracket – you can make one with a jubilee clip and some nuts and bolts
Drain off kits -
Adapter for BMS can if using drain offs -
Caps for drain off valves (10mm, 2 or more if you want spares) -
Follow my guide up to step 2 then skip to step 5.

Option 3: The modified valve, the cans and plugging the head ports
Difficulty 7/10
This is the most comprehensive option which I used and is recommended by Rob Beck. If you are not confident with in depth engine work and tapping, I would not go for this option. Read this guide and you can make up your mind.
For it you will need an RB external kit including the head plugs. In addition, you will need two catch cans and some UNF taps. You will also need at least a valve cover gasket but I HIGHLY recommend new valve cover bolts and to a lesser extent a valve cover itself. I bought the lot because above all I did not want an ongoing problem and restriping the engine bay for the sake of saving a few quid on not buying new bolts was something I did not want to risk doing. If you are confident you valve cover is not leaking you can miss it out and looking back, I should have, but at least I can say I haven’t had to re strip the engine bay all over again.
RB external kit
RBturbo -
UNF taps for head plugs -
BMS catch can - or for 535i
Mishimoto compact catch can -
Custom catch can bracket – you can make one with a jubilee clip and some nuts and bolts
Drain off kits -
Adapter for BMS can if using drain offs -
Caps for drain off valves (10mm, black, 2 or more if you want spares) -
Valve cover gasket and bolts - I recommend using a dealership or someone you know will have genuine parts.
Follow my guide all the way through but you can skip the valve and intake cleaning (step 5) but I don’t recommend it.

Cleaning intake valves (manually)
Difficulty 5/10
Stripping the engine down is the hard part, other than that it just takes ages. If you can, buy a reasonable walnut blaster and use that then if you want some money back sell it on half price or something. Perhaps you guys could get a chain going? To do it the way I did you will need:
Engineers scrappers -{groupid}&ptaid=pla-417435298554&gclid=EAIaIQobChMI066bksmQ4gIVqLXtCh2sWQOGEAQYDCAB EgIWqPD_BwE&mkwid=foR5m6FG-dc&pcrid=314494375343&pkw=&pmt=&prodid=ZT1001791X&slid=&pgrid={groupid}&ptaid=pla-394036231883&gclid=EAIaIQobChMIzd3Wtt_44gIVVeDtCh0Z4gpWEAQYBCAB EgJBJvD_BwE
wire brush set -
Remote engine started/crank (optional) -
Custom wire tools – Not sure what to link. I had some wire I got out of a scrap yard when I was about 12 and I’ve used it for years since for all kinds of things. I used one strand of it to make some scrapper tools that were soft enough to use on the valve stems. Any soft steel wire 2-3mm thick should do.
Engineers scriber (be careful its hard steel) - EgJO3vD_BwE
Intake cleaner, I used this but it’s all the same stuff really (quite corrosive so be careful) - EgI0TPD_BwE

Other tools (if you are doing the head ports)
Good tap wrench, preferably one that is thin and tall but not too tall that you can’t tap the rear most breather ports. I used a custom made one so I don’t know what to recommend sorry!
An extensive socket set with additions to your ratchet spanner extensions and universal joints, this is a good starting point and is what I recently bought, but you’ll need those additional extensions -

Other guides
Here are some other guides on this modification which I recommend reading/watching before attempting the mod especially if you are planning on plugging the head breather ports.
Vid on replacing the valve cover gasket which covers a lot of the work here -
PCV head port plugging - and
Complete guide of installation on a 335i -
Cleaning intake valves with a walnut blaster -
Cleaning intake valves manually , I don’t like how he goes straight in with the spray though -


Research (this guide and others) – It’s very hard to so because some people have a knack for these things and others don’t. But I would say the level of experience and understanding you need is 6-7 out of 10. 10 being someone well rounded in mechanics or engineering with about a decade of experience. You will need to know how to tap a thread in a hole and have good basic understanding of how an engine works and its supporting ancillaries. You don’t have to know every detail about the N54 just the general principles of it all. If you have read this and the previous post and you are thinking WTF then this is not for you. If you skipped lots of it because you already know you’ll be fine. Make sure you read the other guide I linked and watch the videos because If there is something you don’t understand here you might find it in theirs.
Space - You will need a good indoor space to work in with the ability to ventilate it well if you are cleaning the valves manually (e.g. windows). You can chance it with weather and use tarpaulins or covers if you have to but it’s not ideal.
Time - Set aside at least two days but three is preferable. It took me two days for the PCV mod and two more for the valve cleaning (two weekends) but you could do it in 3 days if you didn’t rebuild the engine after the PCV mod like I did. I am reasonably familiar with BMW’s of this era which definitely helped.
Back up - A backup car in case you run into trouble or out of time is a good idea.

Step 1: Stripping the engine

This is the most time-consuming part. I have only given tips on this because stripping the intake and valve cover is very well documented. I have provided links to good videos for this in above sections. The first step is to get to what I consider a basic strip down. This is what I feel is necessary to do pretty much anything in the engine bay and I think anyone could do it.
1. My first tip is for getting out the weather shield. Once you have the covers either side out the way and the pollen filter housing off, stand at the front of the car grab the weather shield and wiggle it in SMALL motions up and down while pulling it towards you. Be careful. The plastic tends to have perished and becomes very brittle and its easy to snap off clips. The rubber weather strip usual comes off with it at the ends.
This is what it should look like. Note the drivers side strut brace is gone because it gets in the way. If you are only changing spark plugs you can just loosen both bolts and move it about as you go but I honestly think you might as well take it out. Use a two pence piece in a pair of plyers to get the small disc out that covers the strut brace bolt.
2. Next tip is for the air box. Its unconventional but I kneel up on the front panel, lean over it, put one hand on the remaining strut brace and get my hand under the far left rubber grommet (there are 3). I pull it up and off. This will be very hard if its cold. In the past I have used a heat gun but be careful! Best way is with a warmish engine. Then I pull the one on the far right which is a bit easier. The front one is final and I do this from standing in front of the car and it’s the easiest. I weigh about 80KG.
3. Put bolts and nuts back on the car once you have taken the ting off so you don’t loose them. If you can’t bag them up with a note of where they go.
4. the charge pipe MAP sensor loom is way too short. Once you have both ends of the charge pipe free, I like to keep it more or less where it is and rotate it along its length (can’t remember left or right) until you can get at the sensor more easily.
5. Remove the manifold before the valve cover then stuff the holes with rags or shop towels. Removing the manifold is fiddly. If you look down into the passenger side of the engine bay you will see a large exposed engine mount. I climbed in the engine bay and put one foot on it and one leg out of the engine bay onto a beer crate. Again, its unorthodox but it works.
7. Disconnect the battery before removing the fuel lines and looms.
8. disconnect the looms around the engine as per the video guides and move the loom out of the way like this
9. loosen the fuel rail nut before the nuts for each individual line. This take some of the pressure out of them. Be ready with some rags to catch the small amount of fuel that seeps out and stuff it under the line nut.
10. an extra person can help to get the valve cover off. Use large flat heads to leaver off the head onto the valve cover. Be careful to use the parts of the head surface that the gasket doesn’t seal onto. You will damage is a bit. Better way please let me know!
11. Once off fill the head holes with shop towel or rags.
That concludes tips for stripping the engine.

Step 2: Plugging the head ports.

I will give as much detail as I can because this is not well documented in the UK. Throughout this process it is very important to take your time and be careful. If you screw up it could cost you a lot of time or money. Make sure you are well rested, fed, toileted and under no time constraints or pressure. If you do not meet these requirements go to bed and square yourself for the next day. A head rebuild because you dropped something into a cylinder requires dropping the engine…
By now your engine bay should look like this.
Make sure all the holes in the head are stuffed with shop towels. I only stuffed the side I was working on which looking back was a mistake which could have gone very wrong, stuff the whole thing. You are doing this to stop things falling into the cylinder. If they do you will probably have to take the head off. Which I have not done so don’t ask me. I know it would be a lick out though so just don’t **** up. Also stuff the intake ports up to the breather ports, see image
Now cover the intake inside towels in the head with white grease. Same with the intake port shop towels. Then fold some paper so it fits into the intake ports and bush it liberally with grease, also brush grease onto the top of the breather ports and the taps themselves. Re apply to all as needed. Put the paper into the port you are working on. The idea is the swarf stick to the grease instead of blowing around. I Have some photos of my own for this but unfortunately I had the battery in my phone replaced and they didn't do a very good job and its now broken so I may have lost them :(
At cylinder 1’s port (the front of the engine) Use a 4mm drill bit put back end into the breather port and holt your tap up next to it. This will give you and idea of what angle to tap at in your mind. You can also see the angle of the ports in the head casting.
Now tap with your first cut tap, 3 in 1 out (you’ll feel the swarf break on the out turns). Take your time and get it square to the port. As the hole is at an angle It helps to push your thumb up against the tap so your thumb acts like the other side of the hole. This will take chunks out of your finger though. Finish this first port off with second and final cuts so you get the idea how it feels. Then when you’re happy do the remaining 5 ports in first cut then go back and do them all in second and final. Each time brush your tap clean and re grease it lightly. You don’t have to tap all the way through. Just enough for the grub screws to go in flush.
Now go back, vacuum the swarf up and wipe the top of the ports clean moving away from the engine. Poke the 4mm drill bit down the port and the blow it out with compressed air.
Next take a grub screw and have some thread lock at hand, preferably red extra strength. With EXTREM care not to drop the screw in the engine (or at all being imperial) put the grub screw in making sure it doesn't cross thread (it should go in really easy if its not) using my thumb again to form the other side of the initial tread wall. I put it in all the way then wound it back out until about have was showing on one side. Then I applied a tiny bit of thread lock, turned it half way in and applied an tiny bit more then screwed it in flush. Once you are happy with it leave it to dry, don’t keep moving it. Repeat for all 6 ports.
Give the valve cover gasket mating surface a final clean, don’t neglect the corners or the hard to reach area on the exhaust side. I have small hands so I got in there easily. But for those of you with hands that embarrass your penis when you are at the urinal, use a large flat head to push some rag or shop towel down there. make a final check before removing the head stuffs. Leave the intake ones in.
You are ready to refit the valve cover.

Step 3: Rebuilding the top of the head

This is definitely easier with two people but I did it on my own fine. The back-corner bolt is hard to get which is why you need an extensive socket set with extensions and universal joints. Nip them all up then follow a bolt pattern torqueing up to 8.5Nm. I went from the centre out.
Now if you are going to clean the intake valves read the next section. If you’re doing them later then skip ahead to step . But its less work if you do them now but I would recommend 3 days in stead of 2. I used two separate weekends.

Step 4: Valve cleaning

With the valve cover back on to prevent the head filling with debris, inspect each intake port. It’s a good idea to take photos for future reference. Either refit or cover the exposed fuel line and injectors. Find an intake port where the valves are closed. You can turn the engine over to close the valves in the ports you want. I used a remote starter but you can also use a jumper lead. I started with cylinder six because I knew it would be the hardest. I removed one of the bonnet gas rods and propped the bonnet open with a piece of wood to give me more room. Then stuff the remaining ports with clean shop towel and then cover the whole lot with an actual towel or and old sheet. Also put one over the white box under the windscreen which holds all your ECU stuff because it will get dirty intake cleaner on it which stains and corrodes plastic.

The hairdresser mobile is not mine!

Now you want to get off as much carbon as you can with it dry. If you go straight to spray or soaking with redx it only penetrates the top layer of carbon which stops is scraping off as your tools slide over the wet surface layer. If you have completed the valve cover replacement the carbon should be quite dry by now. If your engine was recently warm some of the oil in the carbon (same shit) will make it tacky. You can’t wait for it to dry a bit but it doesn’t make a huge difference. Use the scrapers to clean out the worst of it but avoid the valve stems especially if you are using a hard steel. If you do scratch them don’t flip out because if the valves are closed the swept part of the stem and the valve seats should be covered and therefore protected. Once you have the worst of it off you can move into the valve area and onto using wire brushes. Once you are happy you have as much off as possible dry you can move onto intake cleaner, make sure you ventilate the area well by opening windows etc. Spray it in using short controlled burst Marine! And I recommend holding a rag over the port as you do as some can fly back out. Then go back in with what ever scrapper of brushes you have. There’s an image bellow to show you how clean I got mine. Use some compressed air to blow the fluid back out holding a rag over the port again and wear eye protection. If you get it in your eyes (I did) immediately go to running water, hold your eye under it and blink it out. Its quite corrosive stuff so don’t take any chances. If your vison goes funny obviously see a doctor. You can also use a syringe or pipet to suck out large quantities from the port. Small amounts that are leaving a film on the walls tend to evaporate. Rinse and repeat.
That’s it…you’ll be here for hours. Make sure you stay well fed, hydrated and rested because it’s really not worth making a mistake which could mean a head rebuild.
Before and after of cleaning mine manually.
Before and after of someone else's using a walnut blaster

Step 4 pt2: Intake parts cleaning

Clean the manifold, throttle body and charge pipe. It’s pretty obvious spay, brush, wipe. For the intercooler I would leave it until the end because you need to jack the car up. If you have a lift whip it out, chuck some Gunk (engine cleaner) in there, shake it and tip it about then let it soak for 5 minutes, flip it over another way, leave for 5 minutes about 3 times. Then drain out years of crap, flush with petrol and leave to dry.
Cleaning charge pipe.jpg
Intercooler flush.jpg
Now refit the manifold. Be sure to clean the mating surface with a brass brush, brake cleaner works well. Double check the intake ports for metal swarf and lumps of carbon. Use a bore scope if you have one. Fit the new O rings. Getting the manifold on is reverse of the removal. It’s fiddly at the back where it pushes on the intake pipe. Try not to force it but you do need a bit of strength. Refit the wire looms and the junction box etc. Refer to the videos I linked for this.
Once this is back on you are finally ready to start fitting the PCV system components.

Step 5: Installing the PCV kit, cans and drain kits

First off is the RB valve. It should come pre lubed in a bag but if its dry put a little fresh engine oil on it on the O ring side obviously. Be careful putting it in because the valve cover is plastic and the valve is metal. Tightening it up is a bit dodgy. I just made sure the rim of the valve was flush with the valve cover rim.
Next take your new OEM flapper valve and remove the crinkle pipe section from the valve. Using heat helps. I used a lighter but I would recommend a heat gun. Then stick on the rubber pipe from the BMS can kit. Next plug on the Earl’s pro lite hose from the RB kit but don’t cut it to length yet. You can finish up the BMS can and mount it on the strut fitting your drain off kit adapter if you are using them. It’s the 1/8” metal one and use PTFE tape.
Next mount your Mishimoto can. If you used the same can as me you will need the adapters ( ) but I recommended you go for the compact can instead (it’s the same size). Fit your drain off kits if you are using them to. Make sure you use PTFE tape on all your threaded connections. You can mount this where ever you want but it can be hard to find a spot that’s near. I used this spot which required shaving off a bit of the air box. Most of you chavs probably run dual cones to go with your dual man tities anyway. If you don’t check out the image bellow. It allows you to get away with the amount of Earl’s pro lite hose you get with the kit. Note I made a custom bracket on my lath out of aluminium and painted it. The photo bellow is when I adapted another mount and is not the bracket I have now.
Once you have the can mounted you can route the pro lite hose to the can. Bearing in mind what else you’re putting back in afterwards. Once you’re sure you have enough hose you can cut it with about 100mm to slacken it just in case you need to move the can a bit.
Now you need to get the throttle body, and fit the new T fitting that came in the RB kit. If you haven’t already cleaned the throttle body. Pay particular attention to the shaft the butterfly valve rotates on and the mounting surfaces (3 of them). Once the T fitting is on fit the new O ring and bolt it onto the manifold.
Now take the out pipe from the mishimoto can and rout it to the horizontal end of the T fitting. Put the charge pipe back in and put the diverter valves back on it. Unless you’re running a BOV in which case once you have finished masturbating over your self while looking in the wing mirrors plug the diverter valve pipe onto the end that is at a right angle.
Finally, for the PCV kit you can install the drain off kits. Plug in the drain pipes. Now you can route them wherever you want. I routed mine down, to the passenger’s wheel arch. I then zip tied them there and put caps on the ends to stop mud getting in them. I tried a custom metal box but there’s no clearance so doesn’t waste your time. You could also drill some holes in the undertray but I wanted to be able to access them without any jacking up or stripping bits off the car. All I have to do it turn the wheels fully left, kneel down, slide a tray under and open them. These photos are a bit out of date to.
Tip for reassembly, wiggle the weather shield back on carefully up and down. Then tap it on snug with a hammer using the corners/strong parts that won’t be springy and require more force. You can tap it left and right for the bolt holes to line up. I have moved the valves a bit since so it looks better.
That concludes the PCV kit installation. You can now put the car back together and it should look like this.

Step 6: Testing

Check the tightness of the fuel lines one last time. The torque spec is 13NM (also seen 23NM) but I don’t have a C spanner torque wrench so I just went by feel. It’s not very tight though. Start the car up and immediately go to the engine and check for fuel line leaks, then valve cover gasket. Once you’re happy take the car for a short run starting off light. Make sure someone can come and get you before you leave and take a 10mm ratchet spanner with you to disconnect the battery if you need to. Once it’s a bit warmer you can SQUEEZE out a bit more throttle. But don’t go flat out or at least not suddenly. I gave it a couple of heat cycles before I used the car “normally”. By that I mean I took it easy for 2 trips where the car got to temperature (90-100 degrees) and cooled down again before I cained it. If you don’t have temperature sensor for the coolant, I would recommend one. They plug straight into the OBD port and can do basic code reading and 0-60 times. All things she definitely wants to hear you talk about!
Now just drive the car. Check the cans after 500 miles until you get a feel for how quickly they fill up. Most people say the low end fills up 1000-2000 miles and the high end (BMS) doesn’t get much at all. In my personal experience I think you could leave it for 1000 miles for the mishi (low load) and maybe 2000-3000 for the BMS (high load). I checked mine about 500 miles in when I did the valve cleaning and the BMS was empty. The Mishimoto is below.
In regards to the carbon cleaning: Much to my disappointment I felt no difference in how the engine runs and responds even though my valves were quite bad. I speculate that if you run on regular fuel you might notice something but I always use premium so its milkshake anyway (smooth). The only thing I did notice is the revs dropped to about 600RPM once the engine had about a minute to warm when it used to only go as low as about 800RPM.

That’s it, I sincerely hope this helps someone who was in my position and reduces the amount of questions for Mr Beck and Mr Bird! If you have any questions leave a repy or DM me. I have a couple more posts lined up for the near future: race pedals, short shift kit, uprated vacuum lines, Summer air in tyres, seat belt guides, Birds tuning suspension and probably some performance bolt on’s with remapping!

Special thanks to:
Rob Beck at RBturbo
Marshal Lee at ML Performance
Kevin Bird at Birds Tuning
Alex at Hose fittings UK Hose Fittings UK
For all being helpful and patient with my questions. Sorry for all the questions! All of these guys have good stock, great service and know their stuff so definitely check out their websites next time you need something.


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