Engine knock and low oil pressure in the 118i

[ChatMaven]

So the engine began banging very gently the other day, and I stopped driving and never drove again.
The red oil light has been flashing every now and again for a while, so I dropped the sump off today expecting to see chain guilds, but all clear and guided are great, then I pulled the large ends off next and discovered this crank is still perfect with no marks on it.
Will this result in low oil pressure, or should I replace the oil pump anyway? 

[TDudette]

One of the historical defects that caused my red pressure indicator to illuminate at a fairly consistent time/distance (even after the chain and guides were replaced) was the oil pump's balance shafts. This may or may not be related to your issue, but it could have been a contributing factor, as deterioration like that must be attributable to inadequate lubrication at the very least. My warranty replaced the pump entirely, and I've never had a problem with it again.

[ChatMaven]

I'm going to put a new pump in it at the same time, but I've read that if these are old, it could have low pressure.
As I don't know if the previous owners ran it low on oil, causing it to wear out faster than it should have,
Strange, because only the top bearings look like this. The bottom bearings have a few marks but are fine.

[jennycarlotta]

Whip off the bearing caps on the balance shaft, which may be worn, and that will help.
You can run without balance shafts if you remove them from the housing but leave the housing itself in place, and if you put a m10 blanking grub screw into the oil gallery for the balance shafts in the engine block. The oil pump itself is probably OK, but you may save money by cracking open the casing and inspecting the inner workings first.

[Mistral]

Nothing more to say, but Johnny seems like an old-school mechanic rather than a new professional who would just replace a component and watch how it went rather than attempt a repair or fix.

[Geek2232]

Looks like tiredness. No blue, so not from being hungry.
The first one is a little strange because it is mostly on one side. If that was smooth wear, I would say that rod is bent.

Also, pull the mains and give the crank a good cleaning. I'd take it all apart because those pieces of metal are likely to be everywhere.

[ChatMaven]

Just now, Geek2232 said:

Looks like tiredness. No blue, so not from being hungry.
The first one is a little strange because it is mostly on one side. If that was smooth wear, I would say that rod is bent.

Also, pull the mains and give the crank a good cleaning. I'd take it all apart because those pieces of metal are likely to be everywhere.

Thanks for the reply the crank looks perfect not even a scratch on it
Don’t get why the oil pressure light started comming on so gonna put a new oil pump in also just incase

[ForumGuru]

It's not surprising that your oil pressure is low, considering that worn bearings exacerbate this problem by increasing clearances.

[Geek2232]

I'd simply open the pump and inspect it, as the likelihood is that it's good.

[ChatMaven]

I promise to follow through.
Only when the engine was hot did the oil indicator light up.
I tried turning on the air conditioner at slightly higher RPMs, but the light still didn't turn on, leading me to believe that the problem was likely low pressure caused by worn bearings at low RPMs.
Aside from that, you're probably going to take out the oil pump and have a look.
The sump's pressure sensor developed a leak, causing more oil loss.

[jennycarlotta]

Hot idle oil pressure is a typical symptom of bearing failure; furthermore, remove the balancing shaft covers. Consider removing the shafts while you're in there; the smaller n43 models never had shafts in the first place.
A word of caution: the 30 Torx casing bolts are only torqued to 9nm, so don't overtighten them or you'll shatter the mating faces and clog the pump.

[ChatMaven]

Just now, jennycarlotta said:

Hot idle oil pressure is a typical symptom of bearing failure; furthermore, remove the balancing shaft covers. Consider removing the shafts while you're in there; the smaller n43 models never had shafts in the first place.
A word of caution: the 30 Torx casing bolts are only torqued to 9nm, so don't overtighten them or you'll shatter the mating faces and clog the pump.

I'll keep everyone updated on this, buddy. I bought a digital torque and angle tool and have a bearing arriving tomorrow. I also have a secondhand oil pump that came from an engine with a slipped chain.