Instant Low Oil Pressure... Oil Pump Nut?

[MaxVQ]

After 420,000 Km / 262,000 miles, the red oil light turned on while driving.
I stopped the engine and restarted it, but it stayed on.

I drove it for 30 seconds at low RPM to get home.
Oil level is good.

Based on the valvetrain noise (lifters bleed out), there is no oil pressure.

What are the odds that the oil pump sprocket nut came off?
How difficult is it to remove the oil pan to inspect?

Thanks in advance for any tips or suggestions.

2001 530, 5 Speed

[BimmerBreaker]

Not a good thing if you drove it without oil pressure... removing the oil pan is a bit of a chore. First step for me would be to verify the condition of the engine as it is now, especially if it was driven with no oil pressure

[effduration]

It's not common to have the oil pump nut come off unless the car is being raced or frequently goes to red line. But it's possible.

You might be able to inspect it with a flashlight or borescope from the top when you take off the valve cover and vanos unit.

Taking the oil pan off is a bit of a pain as the engine has to be supported at the top and you have to drop the subframe.. But it probably needs a new oil pan gasket anyway.

your issue could be due to a clogged pick-up tube, or some other issue.

[MaxVQ]

Not a good thing if you drove it without oil pressure... removing the oil pan is a bit of a chore. First step for me would be to verify the condition of the engine as it is now, especially if it was driven with no oil pressure

Understood, but I wasn't calling a tow truck for 5 blocks
The last used oil analysis showed normal wear and the engine runs well and makes good power.

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Thanks for the boroscope suggestion, I have a few of them and will see if there is was way to view the front of the oil pump.

[pleiades]

Understood, but I wasn't calling a tow truck for 5 blocks
The last used oil analysis showed normal wear and the engine runs well and makes good power.

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Thanks for the boroscope suggestion, I have a few of them and will see if there is was way to view the front of the oil pump.

Have you tried plugging a gauge into the oil switch hole on the oil filter housing and measuring actual oil pressure? Given the situation, I'm not certain this is a good idea, but how else to determine?

Per the boroscope idea, would it be possible to remove the dipstick tube from the engine and peek in through there?

[MaxVQ]

Have you tried plugging a gauge into the oil switch hole on the oil filter housing and measuring actual oil pressure? Given the situation, I'm not certain this is a good idea, but how else to determine?

Per the boroscope idea, would it be possible to remove the dipstick tube from the engine and peek in through there?

Based on the new and much louder valvetrain noise, I know there is no oil pressure. BUT I will test the oil pressure switch.

As for the boroscope, I don't think it is possible to snake the camera around to the upper front of the oil pan.

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All:
Thanks for your comments and suggestions.

Later in the week, I will check the oil pressure switch, and then most likey will drop the oil pan and have a look at the pump.

[KeysCoupe]

Sudden loss of oil pressure is not a common issue with inline sixes. With your high miles, either the oil pump nut or a fractured pickup tube. Either way, the pan has to come off to inspect properly.
-Donny

[ross1]

Based on the new and much louder valvetrain noise, I know there is no oil pressure. BUT I will test the oil pressure switch.

As for the boroscope, I don't think it is possible to snake the camera around to the upper front of the oil pan.

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All:
Thanks for your comments and suggestions.

Later in the week, I will check the oil pressure switch, and then most likey will drop the oil pan and have a look at the pump.

Don't bother. You already know the answer.
Earlier M60 engines were know for the oil pump retaining bolts falling out leaving only the chain to support the pump which if it didn't result in instant oil pressure loss would stress the pump shaft for the sprocket to the point of failure.
Not sure if this was passed down to the later engines.
Driving it until the lifters were noisy wasn't a good idea.

[MaxVQ]

Driving it until the lifters were noisy wasn't a good idea.

Ideally, you are right.... but I wasn't going to pay for a tow truck to move me about 15 blocks.
Plus 30 seconds without oil pressure at low RPM/low engine load won't hurt/wear anything any more than 262,000 miles already has.

Once I get it running, I'll post a start up and drive video.

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It may not be common, but it is well known:
https://bmwtuning.co/m54-common-engine-problems/

[ross1]

For some reason I was thinking that you had a V-8

[BimmerBreaker]

Plus 30 seconds without oil pressure at low RPM/low engine load won't hurt/wear anything any more than 262,000 miles already has.

That's a very interesting theory

[MaxVQ]

For some reason I was thinking that you had a V-8

Nope... just a sweet six

[sleuth255]

yup, nut is one of the most common failures on the M54. On my list of things to work on when the pan gets dropped next time. Subframe has to be dropped to do this. Not too bad if you have access to a lift or you're in your 20s.

[effduration]

Ideally, you are right.... but I wasn't going to pay for a tow truck to move me about 15 blocks.
Plus 30 seconds without oil pressure at low RPM/low engine load won't hurt/wear anything any more than 262,000 miles already has.

It was 5 blocks in your earlier post..#4 above....was it 5 or 15 blocks?

[capebmw]

That's a very interesting theory

Was thinking same thing.....tow truck=$100-new/used engine $1500.....

[MaxVQ]

Today I dropped the subframe and oil pan.
The nut did fall off and was found in the oil pan!

With a new oil pan gasket and a little loctite red, it will be back on the road

[MaxVQ]

It was 5 blocks in your earlier post..#4 above....was it 5 or 15 blocks?

Oh my god.... so sorry for the typo... I just measured it an it was 5.1234568 blocks. I hope we are OK now.

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Was thinking same thing.....tow truck=$100-new/used engine $1500.....

You forgot the third option... everything is OK.

Engines at low load and RPM can easily run for 1-2 minutes without any damage. Watch a few YouTube videos to learn more.

[sleuth255]

Well, good luck, and may the odds be ever in your favor! Seriously though, the M54 is a good motor and I have no personal XP driving it without oil pressure. I hope everything works out!

[ross1]

Oh my god.... so sorry for the typo... I just measured it an it was 5.1234568 blocks. I hope we are OK now.

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You forgot the third option... everything is OK.

Engines at low load and RPM can easily run for 1-2 minutes without any damage. Watch a few YouTube videos to learn more.

The difference between everything is okay and a spun bearing is a nanosecond. Predicting that moment is the tough part. Piling this abuse onto a high mile motor rather lessens one's odds. I don't think all the hand wringing is necessary though.

For sure at low load and low rpm an engine can survive oil starvation pretty well. Snake oil additive salesman are famous for running an engine without oil as a demonstration of their product's effectiveness. Every one of them I've encountered doing so has declined to allow me to operate the throttle

If it didn't start knocking on the short trip home its probably fine.
Personally, I'd have shut it off the minute the lifters started making noise as I've seen this gamble go south for others.

[KeysCoupe]

That nut coming loose/off usually happens on engines that have been run at high rpm, like track days. Its pretty rare to have one come loose on a daily driver unless your wringing it out. Maybe you should go out and buy a lottery ticket!
-Donny

[seagreen323i]

I had a catastrophic low oil pressure incident one time. Basically I was in the middle of a valve cover job and my father was unaware and asked me to take the car out because he was going to put some gas in it. I totally forgot that I haven't tightened the valve covers down and about 2 miles down the road in a cloud of smoke he immediately shut it off maybe 10 seconds after he saw the message. That was 20k and it's find now.

Sent from my SM-S901U using Tapatalk

[MaxVQ]

The difference between everything is okay and a spun bearing is a nanosecond. Predicting that moment is the tough part. Piling this abuse onto a high mile motor rather lessens one's odds. I don't think all the hand wringing is necessary though.

For sure at low load and low rpm an engine can survive oil starvation pretty well. Snake oil additive salesman are famous for running an engine without oil as a demonstration of their product's effectiveness. Every one of them I've encountered doing so has declined to allow me to operate the throttle

If it didn't start knocking on the short trip home its probably fine.
Personally, I'd have shut it off the minute the lifters started making noise as I've seen this gamble go south for others.

Agreed and understood.
There was no knocking and I will do a quick inspection of the connecting rod play.
Parts are ordered (oil pan gasket and power steering pulley) and should be here in a few days, then assembly starts

[MaxVQ]

That nut coming loose/off usually happens on engines that have been run at high rpm, like track days. Its pretty rare to have one come loose on a daily driver unless your wringing it out. Maybe you should go out and buy a lottery ticket!
-Donny

I've owed the car for 15 years and almost every time I drive it, I have a little fun and shift at 6,000+ RPM... and it still took 421,000 KM / 260,000 miles for the nut to fall off.
I'm going to use loctite red and safety wire to hold it on, so the issue should be fixed for the next 15 years.

Parts are ordered (oil pan gasket and power steering pulley) and should be here in a few days, then assembly starts

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I had a catastrophic low oil pressure incident one time. Basically I was in the middle of a valve cover job and my father was unaware and asked me to take the car out because he was going to put some gas in it. I totally forgot that I haven't tightened the valve covers down and about 2 miles down the road in a cloud of smoke he immediately shut it off maybe 10 seconds after he saw the message. That was 20k and it's find now.

Sent from my SM-S901U using Tapatalk

I suspect the smoke was oil dripping from the unbolted vale cover, onto the exhaust manifold.
The valve cover has nothing to do with oil pressure... it is just an "umbrella" to collect the oil spray.


Anyways, glad it wasn't a big problem for you!

[seagreen323i]

I've owed the car for 15 years and almost every time I drive it, I have a little fun and shift at 6,000+ RPM... and it still took 421,000 KM / 260,000 miles for the nut to fall off.
I'm going to use loctite red and safety wire to hold it on, so the issue should be fixed for the next 15 years.

Parts are ordered (oil pan gasket and power steering pulley) and should be here in a few days, then assembly starts

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I suspect the smoke was oil dripping from the unbolted vale cover, onto the exhaust manifold.
The valve cover has nothing to do with oil pressure... it is just an "umbrella" to collect the oil spray.


Anyways, glad it wasn't a big problem for you!

I am aware of that, but when all of the oil in the engine exits the engine there is no oil to make pressure. Therefor no oil pressure.
Just saying the chances of it being fine are decent.



Sent from my SM-S901U using Tapatalk

[MaxVQ]

I am aware of that, but when all of the oil in the engine exits the engine there is no oil to make pressure. Therefor no oil pressure.
Just saying the chances of it being fine are decent.

That must of been a LOT of smoke!!!

Anyways, I agree with you and think all will be ok. I should have it back together this week and will find out