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Discussion Starter · #1 ·
Hi,

Last year my M5 suffered with a massive over fuelling issue that I never got round to solving. I had the car recovered home because it was undriveable, did as much diagnosis as I could, fitted and coded new injectors (from a car with 19k miles), new spark plugs from the dealer but to no avail. The car was idling whilst I had ISTA doing some tests but then it just stopped and wouldn't start again, just a loud click when pressing start. Tried turning the engine by hand but no joy, engine seized. Decided I was going to break the car as lost my love for it, but after months of never getting round to it and missing my car so much, I've decided to rebuild the engine and bring my car back to life, that's the plan anyway.

Removed the engine and gearbox the conventional way, didn't want to go the BMW recommended method of dropping the whole lot whilst on the subframe, was easier just to remove the front end and bring it out that way. Managed to get the engine in my house and then started stripping everything, and wow, is there a lot of stuff to remove and store.

There was a very strong smell of fuel in the room, which I expected due to the previous over fuelling issue, however it became clear the issue was bigger than I previously thought. The right bank (1-4) inlet manifold was 90% full of fuel, quite a surprise I must say. Next was to drain the oil, which turned out to be a mixture of fuel and oil, probably near on 60/40 oil to fuel. No other surprises as I carried on taking everything apart, very much a learning curve here for me but I'm in no rush and willing to learn.

Removed the cylinder heads at the weekend which was fun, obviously you are supposed to time everything up before removing the chain etc but that's not possible when it's seized. Found a way of taking all tension off the timing chain which allowed me to remove the vanos units and put the chain to one side. To remove the vanos units, I had to use a 20mm and 25mm on the cam shafts to hold them in place whilst using a long bar on the main bolt.

Prior to removing the heads, I had no idea what had caused the engine to seize but after much reading thought it could be related to cylinder wash from all the fuel. I thought I'd find scorched cylinder walls when I removed the heads but that wasn't the case, for the ones I can see they look ok and have no visible marks at all. I now need to flip the engine upside down, remove the sump and make a start on the bottom end, who knows what I'm going to find. Have an engine stand being delivered tomorrow, clearly not going to do this project on the floor :LOL:

Engine stripped and heads removed
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The head bolt that is sticking out on both heads is the only one I couldn't remove. These bolts are blocked by the cog/wheel that connects to the servomotor for eccentric shaft. I need to figure out how to strip the camshafts and variable timing bits next.

Created this post to hopefully get others insights on this and also to provide information in case anyone else in the future has the same problem. I'll be updating this as I go along.
 

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The valvetronic is simple to remove with the correct tool for releasing tension on springs,I bought one last year for doing an n55. Not cheap mind was about £150 I think.

you can do it without though as I did a Prince engine in a mini by levering the spring ‘tails’ off the rockers so I could undo the torx bolt. Refitting I put springs on and torqued bolt with ‘tails’ either side of rockers then used screwdriver to lever back on to the rockers. Far easier with the tool though.
 

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Discussion Starter · #4 ·
I looked at TIS last night on how to remove the inlet camshaft and found the tool needed online but it comes from China and will take weeks to arrive, cost wasn't too bad £140 but I don't want to wait that long. I had a go anyway doing exactly what you said, which was a success, albeit not a nice as it I was using the tool. Managed to remove the last head bolt now which means I can store the heads flat, win win.

Engine stand turned up today, once I've deciphered the cryptic instructions on how to build it, I'll be flipped the block over and setting to with the block, looking forward to that as I think I'll find the cause of the engine being seized.

I did have a look on eBay and although I was tempted, I'd rather go down the DIY route and learn something along the way. I know it's not going to be cheap but hopefully not near 10K.
 

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Discussion Starter · #7 ·
Engine stand built and the engine secured to it, makes life so much easier, worth £100 all day long.

Borrowed a 1m 3/4" bar and 3/4" > 1/2" adapter to have a go at removing the bolt securing the vibration damper. Thought that with the engine seized, I'd be able to undo it but no. Didn't get to applying that much pressure before the engine unseized itself, can turn the crank now but obviously not doing so as I still don't know the cause of the problem.

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With the engine moving freely, I need to secure the vibration damper/crank from rotating so bought a timing kit, I'd need one at some point anyway. This arrived today, quite impressed with it considering the cost, was only £95. Have tried the vibration damper adapter tonight and it's a very good tight fit. Need to borrow the bar again before I can properly test it out.

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Had the sump plug removed for the last 48 hours to let any remaining oil drain out, or at least as much as possible. Whilst this is a good idea, there was still plenty of oil in the engine when I flipped it upside down. When I say oil, I actually mean petrol with some oil in it, my house absolutely stinks to high heaven of petrol now, good thing I love the smell :)

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Set to with taking the sump off tonight as well, the lower sump was a doddle, the upper sump took some time, 27 bolts holding this thing on. The upper sump bolts were very tight and I took my time undoing them, the last thing I'd want is a snapped bolt. The lower sump had some small bits in it, not sure what they are, none were magnetic, unsure what they are.

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Oil pump pickup was clear

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Lots and lots of petrol oil left in here, photo doesn't show everything that dripped out, some of it came through one of the pistons, although not a lot.

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After removing the 27 bolts hold the upper sump on, I could finally see the crank, rods and pistons, have been looking forward to this moment.

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Bearing in mind this is the first time I have ever stripped an engine, I'd like to think I have some idea on what I'm doing and what I'm looking for but for the life of me, I could not see a join in the rod caps. Had my wife take a 2nd, 3rd & 4th look with me but it all looks as one, very deceiving.

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Haven't gone any further tonight as I want to remove the vibration damper before going any further, I highly suspect I need to that before I can go any further anyway. Have had a good look at what I can see so far and haven't seen any marks/scratches on the cylinder walls.

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Discussion Starter · #8 ·
The only thing I noticed tonight was markings on the underside on one of the pistons. Hoping the cause becomes clear when I start stripping the bottom end.

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Still don't know what caused the engine to seize at this point, however it was clearly something to do so much petrol mixing with the oil. Cleaning up was too easy, the "oil" on my hands just rinsed away, I'd love to know the petrol to oil ratio.
 

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Hi,
you won’t see a join line on the rod caps as they are a snapped fit. They are cast as one piece and then cracked into two pieces. This is why you do not see a joint. It is vital they are paired up and go back on exactly as they are removed. You will need new bolts and the tightening sequence is a night mare which is why most people use arp bolts and not bmw with a stretch gauge. Good luck with the rebuild.
cheers
jim
 

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Discussion Starter · #10 ·
Thanks for the explanation Jim, very good to know. I was looking at them super close, comparing with the diagrams on TIS and could not see it at all even though I knew it was there. I'm well aware of the importance of parts going back in exactly the same order, when I removed the caps for the camshafts I had a piece of cardboard marked out with positions. I haven't given the full rebuild much thought as yet as I still don't know what the state of the engine is. I am hoping it can be rebuilt and so far everything appears to be ok.

Can you give any further info on why most people go with ARP bolts over BMW bolts?
 

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Sounds like you are all over what needs to be done. There is a guy on YouTube called Jamie’s garage who is a bmw specialist and he has done a few videos on the bolts and how to install them with a stretch gauge. Worth a look as he explains it really well and there is also another called the car ninja who does a lot of tutorials on bmw engine rebuilds. I’m a mechanic by trade and the information they give is good.
in one of your pictures it looks like one of the Conrad’s is bent but it could just be the picture making it look that way and I wonder if it hydro locked with the over fueling.
cheers
jim
 

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Thinking you might be right about the hydro-lock problem. I suspect there is a corresponding mark on the crank that goes with that scrape on the bottom of the piston and the rod is indeed bent.
 

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Discussion Starter · #13 ·
Borrowed the 1m 3/4" bar again yesterday now that my timing kit had arrived, was quite excited to use the kit and get this ridiculously tight bolt undone and start removing the timing cover.
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Had two people standing on the engine stand to prevent it tipping, started pushing down on the bar to undo the bolt then PING. The slot in the timing cover, where the locking pin goes had only gone and snapped, in addition to this I'd bent this part of the timing kit. Just as before, I wasn't using all my strength at the point of failure and was pulling down straight/in-line with the block. I'm not sure what to do now, a friend says he has an air gun that will undo it but the crank freely spins and there's no way of using the locking slot anymore.
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With Js635d and snowblind both saying about a bent rod, I started removing the pistons, obviously starting with the one in the photos above that looked bent. Result :) :) :)
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Finished stripping the rest, only the one bent rod and all the bearings look in pretty good condition, feel free to correct me.
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Had a good look at the journals on the crank and can't see any markings what so ever, I'll see if I can get a video of this up later on.

Now that I finally know what the issue was, the question is what to do next? I never had any plans on running high BHP but is this now an opportunity for me to upgrade some of the internal parts? It's quite unlikely that I'll ever be in this position again with this particular engine.
 

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Just out of interest was there a corresponding scuff mark on the crank web next to the scratched piston?

And once you work out how to fix the crank from turning again you might find that someone like Mr Clark here can assist with undoing the bolt.

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An impact gun will hopefully free the pulley bolt. A good thing with impact guns is they generally do not spin things such as the crank so that should not be an issue. A bit of gentle heat may also help. That rod is well bent and at least you know why it locked up. I am assuming the petrol in the oil is an indicator an injector potentially failed and filled the bore with fuel causing hydronic lock and bending the rod. Enjoying watching your progress with this.
cheers
jim
 

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Discussion Starter · #17 ·
Every day is a school day and I learnt something today although looking back, it is blatantly obvious and now I feel an idiot. Yesterday I tried to undo the vibration damper bolt whilst using a tool that came with the timing kit, big clue here. After watching some S63tu rebuild videos today, I noticed when the guy was tightening the vibration damp bolt, he had a tool that was similar to mine but far more significant and bolted to the engine. This is when the penny dropped, the bit of kit I've got is purely for positioning the crank/pistons when timing the engine, it came in the timing kit after all :rolleyes:. Need to find the right bit of kit now, at minimum for when I start rebuilding. Have found a replacement chain cover on eBay for £80 so not the end of the world.

I haven't had time to do a video and get it uploaded etc so I'll add some photos of the crank journals
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@snowblind I've had a good look and the only mark I can see on the crank web is very minimal, looks worse in the photo than it does to the eye
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Next tasks are to take the block to my friend and hopefully get the vibration damper bolt undone, then I can remove the water pump, chains, guides etc.
 

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Discussion Starter · #18 ·
Not much progress on the engine lately, need to buy the tool that locks the crankshaft to the belt tensioner bolt hole but I'm reluctant to buy another kit just for this one tool.

Have been weighing up my options on which route to go with the rebuild, should I rebuild with OEM parts or after market parts is the big question. I still haven't decided but thought I'd share my findings so far.

BMW Parts
Con rods, con rod bolts, con rod bearings, main bearings and pistons come in at £4,358.33inc VAT

Aftermarket Parts
Lots of different options here, from different suppliers as well, none found so far are in the UK

ItemCostNotes
ACL Race Con Rod Bearing Set£212.568B1578HX-STD (+0.001" extra clearance)
ACL Race Con Rod Bearing Set£212.56
8B1578H-STD
ACL Race Con Rod Bearing Set£212.568B1578H-0.25
CP Carrillo Con Rod Set£1,839.96WMC Bolts included, CARR upgrade +£320
CP Carrillo Con Rod Set£1,647.18WMC Bolts included, CARR upgrade +$475
CP Carrillo Forged Pistons£1,719.62No extras, various CR available
CP Carrillo Forged Pistons£1,930.82HD pins, various CR available
CP Carrillo Forged Pistons£1,930.82Dome coating, various CR available
CP Carrillo Forged Pistons£1,930.82Skirt coating, various CR available
FCP Con Rod Set£938.05ARP2000 5/16" bolts included. 138.2mm length
JE Pistons£1,962.51Skirt & top coated, CR 9.3:1, No options, rings extra
JE Pistons£1,962.51Skirt & top coated, CR 10.0.1, No options, rings extra
JE Pistons£1,583.96Includes ProSeal rings, Pins locks and Tuff Skirt Coat, Other Options Available
VAC Motorsport Rod Bearing Set£447.96High performance, coated

I realise I've listed a lot above, some are which the same but from different suppliers, wasn't sure if I could include links so left that out.

Comparing the OEM costs against the various aftermarket options, the costs are very similar, albeit main bearings aren't listed in the aftermarket options as I haven't found any yet, main bearings aren't a significant cost anyhow.

One thing I find very intriguing is the difference between Carrillo con rods and FCP con rods, both look very similar on spec but the cost is vastly different and I can't figure out why.

I've done some reading about compression ratios and it would seem that lowering the compression ratio has some positive benefits when running bigger power, which isn't something I've ever planned for but here I am doing a rebuild.

Has anyone reading this done a rebuild similar to this? It would be great to hear some real life experience. I really don't know which way to go as yet but I don't want my project to come to a standstill.

Whilst the engine is in pieces, is there any benefit in having any crank work done? I'm not going to strip this engine again so will do everything necessary whilst it's in pieces.
 

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Discussion Starter · #19 ·
Quick update as all I've done lately is researching parts, reading and watching videos, which has been really beneficial. I've spoken to a couple of different engineering places, one who gave me great advice, in that it's best off having the crank checked over before investing heavily in brand new parts, all this for £90+vat. I dropped the crank off to him today, he is going to check the crank isn't bent, polish the journals, check for roundness and also the journal measurement which will aid me in what rod bearings I need.

Took the block round to a friends garage the other day, he very kindly used his 3/4" impact gun to remove the vibration damper bolt, only took a few seconds, box of beer for the man :)

Having looked at the main bearings, the wear seems to be ok, although interesting it looks more worn on the rear set (cylinders 3, 4, 7 & 8 end) than at the front. Asked the engineering chap if he would need the timing chain sprocket removing before dropping off, thankfully he said no but if needs be he would remove it for me. I don't have a 3 pronged puller, although would happily buy one, it was just that TIS states it needs heating up to 60c to remove.

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Engineering chap said he would need a day or so to get the work done due to workload, no immediate rush on my side is there :D. Hopefully all will come back ok and then it's time to make a proper decision on parts.

During my research I've come across a couple of companies (engineering chap included) who do dynamic crankshaft balancing, which is around £500 but definitely recommended to be done, only thing is you need rods & pistons for this, which I'm yet to decide on. There's also Ultrasonic Cleaning and Hone & Alusil bore treatment services. This project could get expensive but I'm invested now and am really looking forward to having my car back, hopefully.
 

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I am about to start overhauling my S63tu M6 engine. Currently I plan to go with forged pistons, forged connecting rods, and strengthened bearings. The manufacturer I am currently planning to buy is pure performance forged pistons for alsil, I-beam forged connecting rods, and ALC bearings. However, what I am worried about now is that the forged connecting rods weigh 565g. They seem to be heavier than the stock 548g. I am wondering what kind of results this will produce. What do you think?
 
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