Bought a 2008 R55 S that had motor issues from a guy this past summer. The guy's mechanic buddy had already removed the engine from the car and took the head off and found the #3 piston was missing a piece. I managed to get it home on a tow dolly after I put the front struts back on. This is how it looks now:



This is what I found after taking the engine apart:







The cylinder is deeply gouged probably greater than 2mm deep. I don't think it can be saved with a rebore, but I haven't taken it to a machinist yet.



My first thought was that the car suffered a timing chain failure, but the #3 valves look good to me.



Any idea what caused the piston to fail?

Looking to start ordering parts to install an engine I got of ebay for what I think was a good deal. (those N14 engines are more expensive than the n18s.) I've ordered a valve cover gasket and oil filter housing o-ring, what else needs to be replaced since I've got it all apart? I'm more of a 1st gen guy, but there are alot of 2nd gen basket cases out there for pretty cheap. I got this one for $1100. The exterior and interior are perfect and only had 59K miles when the piston gave up the ghost. Thanks.

 

If that was closer to the center I would say the piston melted by the looks of the side.

 

i dont think the piston melted. Most likely, the spark plug broke and caused that.

Ive seen it a couple of times.

 

Wouldn't you see more damage with the fragment of spark plug bouncing around the chamber?

Can you suggest what else I need to consider replacing while I have the engine out? Gasket, o-rings, ect?

 

Not really. Once it brakes it gets squished by the piston in less than a second depending on rpms.

when i got this job from a fellow NAM, it was pretty much a full rebuild. you'll have to replace the block, and while you there you pretty much can replace bearings, main seals, rings, then valve stem seals.

 

Sorry, not asking about the block itself, asking about other things I should be doing/replacing. Like I said, I'm a 1st gen guy and do not have any experience with 2nd gen cars and their problems. I gleaned from scanning the 2nd gen board that maybe a catch can, turbo oil line replacement, vacuum pump delete are things that should be done. That's the kind of stuff I'm asking about.

My plan is to use this engine's crank and main and conrod bearings on a 2009 MCS that I bought about a month ago with a slight rod knock. But I won't know for sure until I drop the pan.

I'll admit it, I'm an addict, I love to fix broken cars. My two oldest kids have R53s that I rehabilitated. Really this is all an exercise for my ultimate project which will be a LSx swap into a smallish car.

 

Took the block to the machinist and it is pretty much toast. The head looks good so I'm going to get it ready to use on the 09 MCS.
Sorted the fasteners that I got with the car and ones I got with the rebuilt engine.



Managed to find the bolts to put the motor and transmission mounts back on the frame. Kind of difficult to figure out where all the fasteners go when you didn't take the car apart.

 

 

Thanks for chiming in. The guy I bought the car from said that it ran rough and then shut down. The car is bone stock, no tunes, etc. I know he went by Mini's recommended oil change intervals and he was the second owner. I assumed it was a timing issue, but the valves in the head look ok to me. It only had about 59K miles when it broke down.

Like I said I took the block to the machinist who said most likely it is toast, but he would have to rough bore it to see if the damage is too deep. I really didn't want to spend the money to see if it was salvageable as I don't want to spend big money on larger pistons. I have another 2nd gen (09 MCS) that is still running but has a slight rod knock. My thought was to polish the crank from this car and use it on the 09 with new bearings and a hone job, the total seal rings that you used on your r55, and refresh the head from this r55 to use on the 09. That would leave me with an extra head in good used shape that I could sell or keep as a spare (wife hates my "spares").

Did you replace every gasket and o-ring when you did your engine? Any particular brand or original mini?

Every time I go to put a part on I have to go to realoem to find the bolt size and then spend some more time trying to find the fastener from the small bits organizer. I know I have a few parts and many fasteners missing. I just bought the heat shields to the turbo and cat from a local guy who parts out 2nd gen cars.

 

 

When you say keeping rotating assembly together, I take that to mean keeping the crank and piston/conrods together. The problem I have is if the 09 MCS has damage to the crank and/or conrod from the spun bearing then I have no choice but to use this crank, which has perfectly smooth journals (I'll still get it polished) with new bearings and reuse the three good pistons/conrods and one of the good ones from the 09 MCS. I'm just thinking worst case scenario. Best case scenario is that the conrod and crank in the 09 MCS are fine and just needs new bearings. Otherwise I will still be using at least one piston/conrod from the other motor.

Check out the responses I got when I asked about the ebay gasket sets: https://www.northamericanmotoring.co...-any-good.html

 

 

I split the difference and got a Fel-Pro set with the exhaust manifold gasket as I already had a spare head gasket. Would you share where to get the main and rod bearings from the UK? Since I may be switching blocks and rotating assemblies how would I go about determining which main bearings to buy? Thanks.

 

 

Thanks for the links. I was under the impression that I have to find the code on the block and the one on the crank and use a chart at the dealer to order the correct bearings. I vaguely recall some guy building up his engine on a thread and posted the bearing charts.

For posterity's sake the Fel-Pro kit I ordered is the HSU 26454 from OSCARO for $122 shipped.

 

 

My Fel-Pro gasket set showed up today. Replaced what I could. No sure where these go:



Going to the machinist tomorrow to drop off the valve stem seals. Going to cost be $375 to get the head done. Not sure why I didn't do it myself, but I could not deck the head myself.

 

 

Thanks for that bit of info. What about the other 2 white ones, exhaust cam? I have changed out the o-rings for the vanos sensor, temp sensor, cam position sensor, water pipe o-ring, thermostat housing profile gasket and water pipe interface o-ring, vacuum pump o-ring, intake manifold gasket, throttle body gasket. These are the last of them but can't figure out where they go. The packaging notes are very sparse.

I gave my head to the machinist without the cams, so I guess I be putting on the teflon rings. Had my head decked and refreshed with new seals and valve guides for $378. I think that is reasonable. Will post up pictures when I get it tomorrow.

 

Triangular metal seal sits between the intake cam adjuster motor "VANOS Valvetronic Motor" - N12 engine only (base model, could be N16 as well). I believe the purple O ring is for another base model part N12/N16 only.

 

 

This is actually the first engine that I have cracked open, ever. Don't know about the limits, but the head I had refreshed, they just cleaned up my valves, installed new guides and seals. If you are desperate you could always get online and find a copy of the alldata that has been cracked. As far as the block is concerned, you probably want to get it decked and get a flex hone that is as close to stock bore (77mm) as possible. I think that is the 83mm one. If you want to get factory internals why not buy used. I'm not going for power, just longevity, that is why I'm sticking to factory (used) parts that my machinist will mic to make certain it is within spec. This will be on my next project since I purchased a used motor that was refreshed by a mechanic to a really good price.

 

You are right, part #11127560273. Couldn't find the purple one.

 

 

Head is nice and clean. So the entire job of decking, testing, valve job, new seals and new exhaust guides was $378. Just need to reinstall the lifters.



The purple o-ring is not for the BOV.

My machinist wants $150-170 to bore and press in some sleeves to save the block plus $200 for the four sleeves. Then the block will still need to be decked. I can get a good used block for about $300 so it is not economical to try to save the block. He also said if you want to hone a block that is in good shape take off about half a thousandth. He also said that you can go by the charts but you can safely use standard aftermarket bearings as well.