Carcaine

2017 autumn bought the car, was looking into small funky cars for a wile already and Mini Cooper S R56, engine code N14B16, seemed an option ticking quite a few points for me:

• price
• looks
• performance around corners

After checking few cars, noticed this one in deep yellow. Couldn't manage myself to thing rationally there and didn't check engine at all, it started and run, that was it I cared about that moment..

Interior and exterior were my concerns, which were and are great, thought I could handle any engine issues later on. Driving home noticed less power than expected and bit rough engine work on idle, also consumed some oil, quick google and a lot people were reporting oil consumption on n14b16, so decided to look into those problems later.

After about a year of daily commute and not feeling that happy with engine performance, doing regular oil service, around June 2018, decided to look into power issue causes and run down hill quite heavily. Did few tests:
1. Compression per cylinder, bar

1. 10
2. 11
3. 12
4. 4 (here we go)

2. Leak down cold engine, %

1. 85
2. 80
3. 20
4. 90

Noting that healthy engine should have up to 20% meantime 3 of 4 cylinders had almost no restriction for air coming in, meaning flow by gasses were passing down into crankcase and making hole bunch of pressure.

Decided to take the head off and visually inspect pistons and bores. Found nothing promising there - bores had tiny vertical scratches, top ring gap was way to wide, could feel a wear point at the top of bore by hand.

All that totally explains leak down results, power loss and rough idle..

Inspecting the head - huge layer of carbon deposits on intake valves, this most probably is caused by huge flow by of compression and, as later was found out, not functioning PCV system, which is integrated into valve cover. Had to replace valve cover later on with new piece.

Head was given to machine shop for inspection - they found out that valve stems were needing replacement, I decided to go with fixing old engine and gave green light for head refreshment. Valve seats/valves were re-shaped to have 3 angle seating.

OK, so how about bottom end.. Disassembled, found no dragons or kitties, passed engine crankshaft and block with pistons to the same machine shop.

After measuring things, conclusion was:

• 1 of 4 pistons could not be reused, too big wear on the skirts
• more importantly, bores were wear out so much, that re-boring into +0.5mm was needed, which means oversized pistons
• and to make things ever worse, crankshaft was needing re-machining 

Yet because had small engine rebuild experience previously decided to go into engine rebuild journey which took me quite a wile, didn't think it will take that much to be honest. Around 3 months, one of longer processes was finding pistons. I went with standard oversized ones, by standard I mean not forged or racing ones. Was planning to use the car daily with standard on slightly raised power. Did disassembly and assembly myself, machine work like reboring and head refreshement taken care by machine shop. 

First I bought Yenmak brand pistons which comes with rings already, it's Turkish company, never heard of, but I am not into engine rebuilds every day and there were no better option I could find at the time. Got those after 2 weeks from ordering moment, packing and description seemed professional, what could be wrong you ask? Very wrong was that 1 out of 4 had 0.04mm bigger skirt from what is declared, meaning if machine shop bores same holes for all pistons - 77.5mm, you end up having no tolerance for that one piston, meaning after you start the engine it will be scratching bore surface right away. Not something you would like to have with fresh engine :)

Was advised by the machine shop to get rid of those Yenmak pistons and look for something else. 

And I did, took me few weeks to return those and 2-3 weeks to order different ones and pass then for the machine shop for re-measurement.

Those were Sonne Kolben, another never heard brand to me, but there was nothing, literally no other choice I could find, which wasn't sport/forged pistons.. I didn't think about no nane brand too much, I have heard of brands like CP, Mahle and similar, which do not make standard aluminium oversized/rebuild pistons for N14B16. 

Ordered pistons, 2 weeks later, got them, passed to the machine shop guys, they approved it this time, tolerances as declared and block re-bore could be started, fuff big headache had been finished at that point.

Crankshaft was also needing re-machining, decided to go with one from another car. Found out that crankshafts in BMW engine N13B16 were having same part number and found one on ebay, fun fact, local company was selling it, contacted them directly and bought that sucker, measurements showed that it was healthy piece, was quite happy there with my decision.

This is list of parts I changed to new ones:

- oil pump

- all bearings (King brand)

- pistons and rings (Sonne Kolben)

- con rod, camshaft, crankshaft bolts 

- timing chain set

- thermostat 

- clutch kit

- most of rubber and copper gaskets and o-rings I could spot on the engine, which potentially create a problem

As someone would say, as there already - lets fix things around.. 

What is good about Mini being under BMW, is that you can order every o-ring or bit you need online and have it shipped  next week. Most happy about oil filter housing gaskets replacement cause found those split apart.

It totally explains small loss of antifreeze over time, and also oily area down there. Oh, also replaced plastic hose which connects thermostat and water pump, had cracks around water pump seal.

Here goes random photos of engine assembly:

Had measured con rod and main bearings clearance with plastigaude and it were just great 0.05mm. Above we can see some plastigauge spots to clean with carb cleaner.
Note: have torqued with old bolts stage 1 only, was advised to not torque all the way cause it's aluminium block and not stud system, so saving block threads there. Used new bolts for aasemmbly anyhow.

Measured axial play with original crankshaft and one from N13B16, had exact same play, which was interesting!
With old bearings - 0.16mm
With King bearings - 0.18mm
With new original bearings from BMW - 0.2mm

Interesting thing that Haynes manual (not worth tbh cause newtis has most info for free) specifies 0.015-0.05mm for petrol engines and up to 0.32mm for diesel ones. My machine shop guys specified ok axial play to be 0.05-0.1mm.

First I bought Kind bearings which were off from both sources of specs, so then ordered original ones, which were off even more. Had no other option there, no one makes oversized axial play bearings for that engine yet, so went with Kind ones and 0.18mm axial play.

Have measured ring gaps, were just as specified, which means boring was good and pistons are not crap this time.

Didn't like con rods piston finger bearing colour and wear of those grooves for oil to go down, so bought set from BMW N13B16 again, those had better shape.

New seal there.

New clutch set.

Cleaned every bit I could access, which helps to see leaks and to have clean engine is required by my OCD.

Home made engine lift, worked like a charm.

Timing being set.

Those plugs for 2 lower block section bolts done with metal epoxi.

Deleting noise maker.

Installing oil pressure sensor, turned out it is shitty one, cause is 1bar off from mechanical one readings. Through it out now, left mechanical one for now. Btw, pressure is on target. 1,6 idle, 3bar on 3krpm.

Old valve gasket had crack, also PCV were off, replaced with new piece, fixed vacuum issue, where I could not lift oil cap normally, there was too high vacuum.

Some oil right away with old valve cover after first start couple hours of engine work, will check later on how new cover handles oil vapour and hopefully way less blow by impacts it in good way.

Biggest help there to cheer me up :)

Almost there.

Special tools I used
- feeler gauge
- plastigauge
- niutonmeter
- simple obd reader

Manuals
Haynes online manual, 18eur year subscription, switched to newtis after found it out
Newtis, free one, recommend it

First start
After rebuild first start went fine, no big surprises there, was happy about it.

So far so good, oil pressure good, engine responds normally. Looking forward to put more km, 800 so far and 2 oil changes. There were tiny metal pieces in the filter, non steel ones, hope to have non with upcoming oil changes.

Found couple unrelated to my fix issues right after rebuild:
- cracked valve cover, were small oil leak could be seem by an eye, also too high vacuum in the crankcase indicated PCV valves were not functioning correctly - fixed with new valve cover
-  acceleration was not linear from idle rpm, meaning there were some sort of hesitation of power increase with little gas pedal movement. It made sense when "throttle body temporarily stuck" obd errors started to pop - fixed with another used throttle body, from some Peugeot with 1.4 N12 engine

Funny thing about this throttle body from non-turbo N12 engine, it had small piece of plastic which did not make any sense in a sense of usefulness, which made only difference from original turbo one, cut that off and fit perfectly.