Good to know, as my 325 also sees the occasional HPDE. How many miles? 187k on mine, hoping I make it to the next time I remove the oil pan.

 

240k on the engine at the time of it's demise.

 

Oil pump nuts were never an issue until the (then) new generation of twin cam 6 cylinder engines. Starting with the M50-S52 and the M52 TU-M54 engines.

Since then ANY car possibly going to Auto-X or HPDE gets the safety wire and/or the bend over locking tabs to secure the nut to the oil pump..

Sorry for your issue....

 

Raised rev limit is the culprit.

 

You may be correct, but I find it hard to imagine how it could last 30,000 miles after last track day with a loose nut.

 

Were you making full use of your rev range? I track quite a bit and I'm super paranoid, so I just short-shift at 6K even if I'm in that awkward situation where I wouldn't have to shift for the upcoming corner, as I'd just hit redline right before hard braking

 

Yes, the point of the Shark Injector for me was the raised rev limit so I could avoid shifting into 5th on the back straight at Watkins Glen. It was significantly quicker when I could stay in 4th, and I was told the harmonics of the 2.5 were not as severe as the 3.0, so no worries. Live and learn. I'm still not sure that was the issue, because that was 2 years ago.

 

I think you are misinformed, the reason for the nut issues is the lack of a chain tensioner. This causes severe chain slack when RPMs change quickly (as they would during a track day). The extreme forces from the chain whipping around eventually backs off the nut. The proper fix is to install a chain tensioner: Upgraded M52TU/M54 Oil Pump & Tensioner

 

I think you are misinformed, the reason for the nut issues is the lack of a chain tensioner. This causes severe chain slack when RPMs change quickly (as they would during a track day). The extreme forces from the chain whipping around eventually backs off the nut. The proper fix is to install a chain tensioner: Upgraded M52TU/M54 Oil Pump & Tensioner

I mostly agree. But consider this:
E28 M5 & E30 M3 are bereft of a lower (oil) chain tensioner. Slop and jump around (chain vibration) all the time. I've yet to see one come loose that was properly attached.

Also when at the track; There's additional forces at play. Heavy acceleration and very hard braking. If no pan baffle is installed there can be momentary starvation of the pump. When the oil resumes through the pump (could be a 500Ms gap) there's a shock factor when the oil hits the rotor/stator.

I had a V/G customers 1994 540i in here last year. Heavy leak from the lower oil pan. So we pulled the pan to change the gasket. We were shocked when we saw the nose section of the oil pump and the nut (snapped just behind the thin nut) sitting in the pan. We gasped.

Pulled a main and a rod bearing for inspection. All was just fine. The gear was sitting loosely on the splines. Imagine that...! One good deer stop and it would have been game over for that engine.
P.S. The pan, pump etc. were all original.

 

Agreed.

 

On the O-ring, could it be one of the oil filter cap shaft rings?

 

Or maybe the dipstick tube o-ring, but I'm confused about that little plastic tab that was attached.

 

I would install a 4 bolt oil pump shaft and the tensioner too

 

Since this is not my regular track car, I suspect that at a minimum a safety wire + loctite should now be good for the street. But "once bitten, twice shy", I ordered the 4-bolt shaft from Bimmerworld for my replacement engine so I don't have to think about it.

 

Since this is not my regular track car, I suspect that at a minimum a safety wire + loctite should now be good for the street. But "once bitten, twice shy", I ordered the 4-bolt shaft from Bimmerworld for my replacement engine so I don't have to think about it.

Good for you, I consider the safety wire more of an indication that a bolt unlooses and not a shoot and forget means of securing. Also, a tensioner isn't that expensive, but with the 4 bolt shaft you will be golden

 

When I break engine things on the race car,
it tends to happen on tracks with long straights
when I get the gearing just a bit short.

Harmonic vibrations seem to be worst when the engine's
held at maximum RPM and NOT at maximum loading.

t

 

When I break engine things on the race car,
it tends to happen on tracks with long straights
when I get the gearing just a bit short.

Harmonic vibrations seem to be worst when the engine's
held at maximum RPM and NOT at maximum loading.

t

Ouch, seen that a few times, Thankfully not personally.
Yeah the whole " What differential for XX track."
My biggest issue was The Glen. It was almost impossible for me to get it ALL correct. It was all fine except the short chute between 8 & 9. Rev the piss outta 3rd. or down low in 4th. Only to have to downshift again in a couple of seconds for the left-hander back onto Nascar... The issue would have to be solved inside the trans and not @ the diff...

Second order harmonics are a bitch.

 

I did the Drilled Oil Pump Nut with red lock tight but I am still concerned about it.

 

...yeah, stock BMW transmission ratios are anything but 'sporty'.

I used a NISMO gearbox for a while. With the right diff, it had a gear for every situation.

t