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Old BMW Engines in the 1990s (Engine code M52tu, M54, S52) have a problem where the nut holding the oil pump gear vibrates off with sustained at high RPM (e.g. on a track). The consequence of this is the pump gear falls off the shaft and oil pressure is lost.

At high RPM (5000 rpm+), once you get a oil pressure low light on the dash, how much time do you have to shut off the engine to avoid catastrophic failure?

This assumes the engine was properly warmed up and running normally prior to sudden loss of oil pressure.

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That's a very subjective question, without a real "it will be xxx seconds to catastrophic failure". The reason being is, it depends on a lot of factors, such as:

  • What kind of load is the engine under when the failure occurs?
  • What kind of oil is being used in the engine?
  • How old is the engine?
  • Has proper maintenance been done to the engine?

The best answer I can give you is, if the engine is shut off directly when oil pressure drops, minimal damage will result and the engine should be okay. When oil pressure drops, there's still a film of oil on the moving parts which will protect it for a period of time. There's no set "this amount of damage will occur" because it all depends on the factors I wrote above and many more I haven't thought about. It most likely won't self destruct in a matter of seconds, but rather minutes. However, engine damage will most likely be occurring during this time. How much? Who knows. Again, factors.

The reason I can come to this conclusion is, I've watched too many videos of where people are intentionally draining the oil out of engines and running them until they seize (which happens more often than it self destructing). In these videos, the engine ultimately seizes (obviously), yet it usually takes upwards of five minutes or even more for the seizure to occur.

A better plan for this would be to fix the issue and not wait around for the bolt/nut (whatever it is) to drop off the gear and allow all this catastrophe to occur in the first place. You could the nut with a self locking one, which would keep it in place without the worry. You could also pin the nut as well. There are many solutions which do not end in "Well, it's like this, the engine blew up." Take care of it before it's a problem.

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  • What I was trying to understand was e.g. timing chain failure means immediate destruction in an interference engine. Engine overheating = few minutes before head warpage. Where does loss of oil pressure lie? Problem is much harder than fixing the nut as the pump shaft will break if the nut doesn't loosen.
    – tgun926
    Jun 3 '20 at 13:25
  • @tgun926 - There are too many variables to answer your question definitively. It could take it anywhere from 2 seconds to 20 minutes depending on the engine involved. Jun 3 '20 at 14:05
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Seconds...

Had to collect a car off the motorway when the owner saw the oil light come on and he said "I looked at it, then realised what it meant, but before I could react there was a bang".

The engine was spread over some 100 meters of road, bits everywhere.

Without sufficient oil, the bearings suffer localised welding and the energy from the movement of the car and the rotating engine forces those welds to break. This can, and does, cause those parts to break as they are not designed to support those forces... con rods break and puncture the block - basically the engine smashed itself to pieces...

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  • That sounds like oil pressure loss was a consequence of another failure. Why would lack of oil pressure cause the engine to physically break apart?
    – tgun926
    Jun 3 '20 at 13:26
  • More than likely, the engine went bang, then the owner saw the light and knew what it meant ... dunno ... people will change the story to suit their narrative, especially when it puts them in a bad light. Jun 3 '20 at 14:06
  • @Pᴀᴜʟsᴛᴇʀ2 well the driver did say that his first thought was “it will be a faulty oil pressure switch...”.
    – Solar Mike
    Jun 3 '20 at 14:17

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