I knew it was rod knock, but optimistically ordered a cam chain tensioner and proceeded into front end service mode. Drained oil looked good, feeling optimistic. Oil filter had fine metal particles... Pulled pan and sure enough #4 rod bearing was trying to escape.


Car only has 60k miles and I'm hyper aware of oil level and changes (Mobil 1 5w30). Any guesses what would cause such premature bearing failure?

 

I crossed my fingers and polished the crank journal and rod with 600 grit paper, thoroughly cleaned and reassembled with new bearing coated in Molly assy lube, new rod bolts and properly torqued.

Sounded great, for about 10 easy miles. Then the knock was back.

So, hunting for a junkyard engine. I've found several in the Los Angeles area (I'm in San Diego) that advertise 70k ish miles. Any way to verify miles? Probably just a crap shoot.

Most of the engines appear to be mostly complete except the super charger is removed.

What should I plan on for the swap?

- Change supercharger oil
- New CPS o-ring
- New thermostat and housing
- New exhaust manifold gasket
- Swap new cam chain tensioner from old engine (or is it now contaminated?)

Anything else I should plan on having on hand?

I'm reasonably mechanically inclined, plan on two full days for the swap?

Thanks in advance for any insight!

Matt

 

Mobil 5-30 is not the bestest oil around, I like their 0W40 better for an FI engine, or castrol. You may be just unlucky or perhaps have a fuel issue on that cylinder.

I would put an new oil pan gasket while it is out and change your sway bar bushings and LCAs while you have access.

 

Why not take the crank out have it checked and machined and replace all the bearings. Oil starvation is the likely cause. Have the rods checked too for roundness. Replacing the bearing isn’t going to work if the rod and/or crank are out of round.

 

Man.....that must have been a hard 60K miles! Are you the original owner? I'm wondering if detonation (wrong fuel octane) could have caused this? I've got 171,XXX miles on my R53....and it's still chugging along great. Just sent an oil sample off to Blackstone Labs a month ago, and they said the oil results look great!

 

So Mobil 5w30 is to blame? Castrol is on the Mini's oil cap so must the the best. And all FI engine should use 0W40?

And no. Detonation seldom (I want to say would not) cause the rod bearing to spin. It is oil starvation and does not take long. Even 0W05 won't cause this.

 

The grade of oil you were running did not cause that. All I run is Mobil1 5w-30...and I've got 170,xxx miles on my motor with no issues at all. Thousands of guys run 5w-30 with no issues.

 

Agreed. The problem was not caused by bad oil choices. M1 5W30 is a bit weak on anti-wear additives, but that's an issue for cylinder walls and the head, not the crank bearings. Either the bearing starved for oil at some point, meaning the oil pump sucked air, or you just had bad luck and the engine came from the factory with too much gap in one of it's oil circuits.

I don't know enough about this engine yet to offer better details,but usually an engine has 2-4 oil "circuits" in parallel. One circuit, for example goes to the crank main and rod bearings. Another goes to the head. The flow resistance of each circuit is carefully designed and manufactured. If any circuit allows oil to flow too freely, then the oil pressure in the whole engine is impacted. Also, an engine will have 1-3 oil pressure relief valves. If one of those is weak, oil pressure will be low. Any oil circuit in the engine with inadequate flow resistance can lead to bearing damage. This is because low flow resistance will mean the pump inevitably has a hard time keeping up when the oil gets hot and thin. The crank bearings will not tolerate hiccups in the oil flow. My point is that bearing damage can easily be a symptom of a problem with oil flow resistance elsewhere. An experienced engine builder knows where to look for tolerance problems that would allow too much oil flow. But I only know old BMW engines, and not this one, having owned a Mini for only a week.

 

And no one asked OP if he had look into the infamous oil drain back valve in the oil filter housing. Please do us all a favor check to see it had dislodged. That will explain why the second set of bearings is trashed too. Get yourself a mechanical oil pressure gauge too.

 

yes that was my issue i wasnt aware of that, low oil pressure, light would turn out once at 3000rpm drove it thinking
it was just the switch sensor, then failure happened with stuck chain tensioner, changed that and timing chain, after pulling oil pan off i saw the bearing bits bottom of pan and number 2 spun bearing also play on number 3 but not back and forth buy side to side....not sure if there is a little play with rods when you wiggle them or they must be tight as...drain back plunger was broken and previous owner cut top cylinder of an old oil filter and placed it on top to hold the broken plunger i didnt know this and took it out thats when oil pressure light came on...fking spewing idiots not doing proper repairs