Hey everyone!
I am new here, I've introduced myself HERE
According to the previous owner, the car was idling in the garage when big BANG happened and the engine stalled.

I've removed spark plugs and here what I've found:



This is the spark plug from the first cylinder: it is a bit damaged and in oil. The rest of the spark plugs are fine:



So, my current theory: a valve met a piston, either due to wrong timing or/and the engine was abused in the past.
Thus, next step is valve cover and head removal. Oil pan too, but this could be done after the head is removed. Stay tuned.

 

Uh oh! Valve met piston could mean a new short block (scored or broken cylinder) particularly if pieces of the valve detached.

 

Right. I recalled that I have an endoscope camera (Android phone attachment). Unf, my crappy endoscope camera can't save photos or videos (even tho it is pretending to), but I went ahead and used it.
The piston in the first cylinder is.... absent. Literally. Desintegrated, I can see the crankshaft and the oil pan through it. The cyl walls seem scorched here and there, but it is hard to tell how bad it is (I assume it is bad: the whole piston (or at least top of it) was desintegrated!) I also see a piece of the valve in the second cylinder, third and fourth are fine.
So, I assume it was a timing issue, probably chain jumped a tooth or two.
Next steps: remove the head and the oil pan.
The main question at the point - is the head and crankshaft salvageable?

Fun begins! I'll keep posting pics.

 

 

I've managed to record the borescope video. Here is the first cylinder:
The second, 3rd and 4th. You'll see a piece of valve (I think it is exhaust one) in the 2nd cyl:

I've also looked at intake valves through the injector holes:

At first I thought the head has a crack, but then I figured out that it is probably just casting artifacts (since the shape of that 'crack' is the same in all 4 cylinders). So, still don't know if the head is usable.

 

It is a shame, the engine was in very good shape...

 

Have opened the oil pan:



Found a hole in the block:


The engine is seized due to piece of piston stuck between the crankshaft and block:

 

Took off the head, it survived:



The first cyl. The damage is minimal:

 

Wow, that oil pan photo is like a nightmare. That must have been quite a bang the PO heard.

 

Yeah, I bet.
Now I am hunting either for a cheap short block (with a good block, cylinders and a crankshaft) and build the new engine on top of it, or looking for a complete low-mileage engine (long block). So far trying to locate something locally (WA / OR), because I want to inspect the motor before paying for it, but it is not that easy: there are lot of cheap W10 motors while not so many W11s. And W11s are much more expensive (even w/o supercharger included). Found W11 with 69K miles for 2K....
Building a new motor on the block is not cheap either. Only crankshaft / piston bearings will cost me $500+, not including the extra rod / piston (another $70) and all new rings for all pistons ($70 * 4)... I.e. only parts to rebuild the short block will cost me $800-900, then add a head gasket, new head bolts, rebuilding cyl head and we are ending up around 1300-1500 (not including the cost of the engine block itself! Which is in our area would cost around 500-650). Thus, maybe buying a whole low-mileage motor for 2K is not a bad idea at all....

 

I think after accounting for the value of your time, your last option is the best one...

 

Small update: the engine is out. I took it out by parts: first the lower half of the engine, then unbolted the torque converter, lifted the upper half, removed the crankshaft with the flywheel and finally removed the upper half. I left the tranny in place (unlike the "classic" way to remove the whole thing - engine with tranny - at once). I hope I'll be able to put the engine back with tranny in place.

 

Just a bit of update: making some progress, but finding parts is not an easy task. Firstly, it was super hard to find another crankshaft for W11 in a good shape. Thanks to fellow northamericamotoringian - I've got one, but I failed to do so on ebay, local junk yards or other online resources. I could have buy one from a MINI dealer or ECS Tuning for $1000+, but I decided that this is a bit of overkill.

Another problem - to get any genuine MINI parts from dealers. I needed new bolts for main bearing caps and rod bearing caps, there are no aftermarket ones for that. I had to wait 1 MONTH to get them from the dealer, because they are in nationwide backordering mode. This means they don't get enough parts from Germany, they froze inter-dealership parts exchange too. Crazy times.

I also had difficulties to find some aftermarket parts, namely the timing chain kit. There are two brands which I trust - EngineTech and Melling - which make the timing chain kit. EngineTech is also on backorder everywhere and Melling is twice as expensive....(still much cheaper than from dealer) Finally, bit the bullet and got the Melling kit from ebay seller (Rockauto had it too, but I waited too long and it went out of stock).

I will continue to post updates here periodically, but for more frequent updates go to my Instagram: https://www.instagram.com/mini_bmw_mechanic/ (I am catching up with pictures on my Insta, soon it will have newer pics than this thread, so - subscribe!)

 

Inspecting the head damage. It got a hit in cyl #1 into the area of intake valves and a spark plug. Both intake valves in cyl #1 are bent, but the damage on the head seems minor. If the rest of the head is fine, camshaft, seats, bearing caps are fine, I am going to reuse the head. I will pressure test it and resurface, of course.

 

 

 

 

 

 

https://www.instagram.com/p/CYS81Wtr5Pw

 

https://www.instagram.com/p/CYS-DvslwaW/

 

 

looking super clean

 

Yup, got lucky with that indeed!

 

An update: the car is done, I am already driving it. A lot of stuff was done on that, if you are interested in A LOT OF details - visit https://www.instagram.com/mini_bmw_mechanic/.