LOW OIL PRESSURE LIGHT, STOP ENGINE, CHECK OIL LEVEL when engine is warm X5 V8 4.4i

[pasken]

Originally Posted by JCL

What do you hope to gain with an additive? It won't fix anything.

I assume if I switch to higher viscosity oil like 20w50 might give enough pressure to not trigger oil light, which in turn would mean slightly better operating conditions for the engine and hopefully slightly prolonged life. Am I correct or no?
By thickening my current oil (5w30) with additive I should be able to achieve higher viscosity oil too. Am I correct or no?
How long it can last in current condition? - are you talking about few hundred miles or more like 3-4k miles or 10k miles?

[JCL]

Originally Posted by pasken

I assume if I switch to higher viscosity oil like 20w50 might give enough pressure to not trigger oil light, which in turn would mean slightly better operating conditions for the engine and hopefully slightly prolonged life. Am I correct or no?
By thickening my current oil (5w30) with additive I should be able to achieve higher viscosity oil too. Am I correct or no?
How long it can last in current condition? - are you talking about few hundred miles or more like 3-4k miles or 10k miles?

Yes, higher viscosity oil may stop the light from coming on. That doesn't mean better operating conditions for the engine, but rather worse conditions. The light is not the problem, it is an indicator of a different problem, in this case likely worn bearings. Putting thicker oil in will cause accelerated wear when cold, so that isn't advisable. The only reason to put thicker oil in is if you want to mask the problem, sell it quickly, and dump it on an unsuspecting purchaser. Some would call that fraud, unless you disclosed the problem up front.

Yes, an additive may do the same thing, but it could have other problems associated with its use, due to compatibility with other parts inside your engine. Skip it.

The light is on when the engine is idling slowly. Live with it. When the engine speeds up it is apparently enough to turn the light off. If you want to confirm it, get a shop to hook up a separate diagnostic oil pressure gauge, and get the readings at idle and above idle. That will confirm the diagnosis, but if it is what we think it is, there is no easy fix. If oil pressure is also low above idle, it could be a worn oil pump, which is a little cheaper than bearings.

Some engines have run for years with low oil pressure at idle. There is no way to tell how long it will go, without tearing it down to see inside.

[pasken]

I was just reading another BMW post Red Oil Pressure Light - E46Fanatics and someone suggested that increasing idle rpms may help and 500 rpms is too low. I have around 500-600 without AC. The picture of OBD scanner I posted earlier was with AC on (700 rpms). It seems strange that I have worn bearings with only 100k miles on engine - is it common for M62 engine? Is there any other symptoms of worn bearings other than low oil pressure? If I take to someone to check oil pressure with gauge - what is it supposed to be? and at what rpms exactly?

P.S.: When I picked up car from seller he said it was sitting for 1 year, and he supposedly replaced oil before I picked it up, but he suggested to do it again because it was very nasty when he did it. Also on my way home on the highway - I did not notice any oil pressure lights, however I would assume it was enough (10 mile trip) to make engine hot. After that I had a few very short trips which probably were not enough to make engine hot. I noticed the issue with low oil pressure light after I left key in ignition inserted and it drained battery quickly. It had to be jumped. After that I tried to drive it some more to get battery charged and noticed the issue at the light after driving about 6 miles (driving hard in Sport). I am not sure if it can be related or not... Also initially when I saw oil pressure light I thought about oil leak and I added 1/2 quart of oil twice - it gave me another 3 miles range each time until oil light started flickering again at stops. After that I changed oil + filter + oil pressure switch.

[steelheader]

There is a plate on the bottom of the oil pan take it off maybe Your oil pick up is clogged ? There could be sluge in there ? You can see how bad or clean the engine is with a light .Your miles are low to have a worn out motor ,unless they never changed the oil.Oil level switch could be going bad also if the guys telling You to change the oil right after he changed it thats kinda bad iam betting the oil filter that was in there when he did it was in pieces and fell apart .

[papasmurf]

It's time for an aftermarket oil pressure gage, but I bet your motor is screwed.

[Skyline]

>JCL
Can you explain why low oil pressure is indicative of bad bearings??? Wouldn't he have some rod knock if the bearings were bad?

I do like the idea of connecting an oil pressure gauge. And I do think it's possible to have an oil pump going south, even if pressure is only low at idle. But I do think the long sit this car had may be a clue to the symptoms, especially since the previous owner said the oil removed was "really nasty". Sounds to me like something gummed up and a motor that did not get proper oil changes. Perhaps a motor flush would help.

[civdiv99]

Not to bogart JCL on this question, so I'll keep it brief.

Oil pressure in an engine is developed by the bearing clearances. The clearance allows oil to form a film that serves to keep the metal surfaces from touching. Sufficient oil pressure ensures that the metal of the rotating shaft (journal) and the bearing shell can never touch, and wear is therefore confined to initial start-up and shutdown. The oil pressure, combined with the rotation of the shaft, also hydrodynamically centers the journal in its shell and cools the bearings. Such a bearing is known as a fluid bearing.

Local pressure (at the crankshaft journal and bearing) is far higher than the 50, 60 psi &c. set by the pump’s relief valve, and will reach hundreds of psi. This higher pressure is developed by the relative speeds in feet per second (not RPM or journal size directly) of the crankshaft journal itself against the bearing, the bearing width (to the closest pressure leak), oil viscosity, and temperature, balanced against the bearing clearance (the leakage rate).
All pump pressure does is “fill in the hole” and refresh the oil in the annular space faster than the leak expels it. Low pressure indicates that leakage from the bearings is higher than the pump’s delivery rate.

So when you have a low oil pressure indication, it means the oil is "leaking" out of the bearing surfaces faster than the pump can replenish it, and therefore you are risking metal to metal contact. One that occurs under load, overheating of that surface and seizure very (very) closely follow.

[Skyline]

Originally Posted by civdiv99

Not to bogart JCL on this question, so I'll keep it brief.

Oil pressure in an engine is developed by the bearing clearances. The clearance allows oil to form a film that serves to keep the metal surfaces from touching. Sufficient oil pressure ensures that the metal of the rotating shaft (journal) and the bearing shell can never touch, and wear is therefore confined to initial start-up and shutdown. The oil pressure, combined with the rotation of the shaft, also hydrodynamically centers the journal in its shell and cools the bearings. Such a bearing is known as a fluid bearing.

Local pressure (at the crankshaft journal and bearing) is far higher than the 50, 60 psi &c. set by the pump’s relief valve, and will reach hundreds of psi. This higher pressure is developed by the relative speeds in feet per second (not RPM or journal size directly) of the crankshaft journal itself against the bearing, the bearing width (to the closest pressure leak), oil viscosity, and temperature, balanced against the bearing clearance (the leakage rate).
All pump pressure does is “fill in the hole” and refresh the oil in the annular space faster than the leak expels it. Low pressure indicates that leakage from the bearings is higher than the pump’s delivery rate.

So when you have a low oil pressure indication, it means the oil is "leaking" out of the bearing surfaces faster than the pump can replenish it, and therefore you are risking metal to metal contact. One that occurs under load, overheating of that surface and seizure very (very) closely follow.

I still think this is a longshot on a 100k mile motor, that sounds and runs 100% normal. I'm not disputing that it's possible to have premature bearing failure in a BMW motor at that mileage by not following proper maintenence, but it's pretty rare. Especially considering the OP says there is NO rod knock or bearing noise. If this were my X5, I'd do a thorough engine flush first. See if the problem remains. Then check the oil pressure with a gauge. If the pressure still reads low, I'd be dropping the pan to take a close look at the oil pump, and see how much sludge is still in the engine after the flush.

[HPIA4v2]

Originally Posted by Skyline

I still think this is a longshot on a 100k mile motor, that sounds and runs 100% normal. I'm not disputing that it's possible to have premature bearing failure in a BMW motor at that mileage by not following proper maintenence, but it's pretty rare. Especially considering the OP says there is NO rod knock or bearing noise. If this were my X5, I'd do a thorough engine flush first. See if the problem remains. Then check the oil pressure with a gauge. If the pressure still reads low, I'd be dropping the pan to take a close look at the oil pump, and see how much sludge is still in the engine after the flush.

+1

most likely sludge build-up, from the symptoms; logically higer RPM increase pressure even on half clogged.

[JCL]

Originally Posted by civdiv99

Not to bogart JCL on this question, so I'll keep it brief.

Oil pressure in an engine is developed by the bearing clearances....

What civ said.

Skyline, this is all just guessing until the OP actually hooks up a oil pressure gauge and starts diagnosing the problem. But we know the engine wasn't maintained properly. And there are lots of bearing surfaces other than rod bearings.

I'd think twice about that engine flush. It will lower oil pressure, unless the only thing clogged is the oil pump.