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

[pasken]

Hi,
I recently purchased 2001 BMW X5 4.4i with V8 M62 engine and 100k miles on the odometer. After driving the car for 6 miles or so from cold start, I started to get "low oil pressure light" flickering at idle engine rpms. After a few flickering it stays on and "STOP ENGINE, LOW OIL PRESSURE" message appears. I stop engine and "Check oil level" message appears. If I immediately restart, "low oil pressure light" will still be on. If I push accelerator - the light goes away. As soon as engine rpms get back to idle "low oil pressure light" is back again.

Obviously I did check the oil level with dipstick and it is full. However when the oil light starts flickering, I stop engine, remove dipstick, and it is absolutely dry(!). I insert it again and it shows full --- I am not sure if it's normal or not. I even waited 3 minutes after stopping engine and the first time I remove dipstick it is dry, as soon as I insert it again - it's full. I can repeat this every time. Very strange. Never noticed anything similar on other cars...

I did some research online and found that oil pressure switch (under the oil filter) goes bad very often. I replaced it along with oil and filter. I used exactly 8.5 quarts of 5W30 Valvoline Synpower and Driveworks filter. It still throwing "low oil pressure light" after driving few miles at stops/idle...

When my mechanic changed oil, I asked him to check if there are any major oil leaks underneath and he said everything is normal - some sipping from valve cover gasket, but nothing major. Also no oil drops on the ground after car is parked for a few days. No black smoke either. Oil filter housing cap is good too - no cracks or leaks.

From what I see the issue is temperature related, because it starts when engine is completely warm. I borrowed small OBD scanner and monitored coolant temperature while driving and the issue starts at stops/idle rpms when coolant reaches 226-229F (or 107-109C - I am not sure if it's normal temp or not). My temp. monitor on the cluster shows exactly in the middle all the time. Engine seems to run fine - no unusual noises, or check engine codes. When the oil light starts to flicker I try to stop the car. I did not run it "as-is" for a long time. By starting A/C (increases idle rpms some) the oil light flickers less, but still starts to flicker.

Anyone can help me? I checked some posts before, but I did not find any definite solution. Someone mentioned "loose oil pump bolts" or debris in oil pick up screen on the oil pump could be the problem, however in my case why does it happen only when engine is hot? I assume it would be all the time or random. Someone switched to 20w50 oil and some oil additive and sold the car without fixing the issue. Someone mentioned about engine running too hot and replacing thermostat fixed the oil light issue. I hope it's not crankshaft bearing or something like that. I am not sure what to think. Do you think $100 dealer's diagnostics will find the problem? Any suggestions?

[TwinTurboGTR]

Well first dump the Driveworks filter and go get OE from BMW. The stick being dry after you shut the motor off is normal. The motor has sucked in most of the oil and needs time to flow back into the pan.

As for the pressure, it does sound like a switch problem, but since you replaced it and the problem still persists, I want to say it is the viscosity of the oil. But depends on how cold the temps are.

Did you mention once the motor warms up to OT, does the light then stay off?

[pasken]

The outside temp is 40F. When motor is cold or slightly warm no warning lights at all. After I drive it for 5-10 minutes and coolant temp reaches 226-229F (is it operating temp?) - oil pressure light starts to flicker and in a minute stays "on" only at idle. If I give it 1000 rpm or more the light goes away. So when i drive it, the light is off. At stops - "on". Here are some OBD data with AC on and oil light slightly flickering:



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[subieworx]

It's a bearing clearance issue. As the car reaches temp and the oil heats up the viscosity lowers causing lower pressure. At idle the pssure is low enough to trip the light. Over time, and probably not much, you will have issues with rod and main bearings.

[pasken]

So what should I do with it? Rebuilding engine is not an option... Should I try 20W50 oil and oem filter? Do you think it would help? Should I try some oil additive before dumping money in another oil change?

[civdiv99]

It's a 12+ yr old car with probable oil pressure issues. If it was me I'd monitor the pressure with an after market gauge since that'd answer most of your questions pretty quickly.

Don't expect dealer to be able to fix anything, but they'll be more than happy to suggest replacement items, and you won't like the cost.

The temps you see are indeed what BMW has for the intended operating temp. And while lowering the temps may be desirable for a lot of reasons, it isn't a fix for your situation in any case. IF your internal clearances are excessive, which is quite probable, then what you have is a very worn engine on borrowed time.

You can try some high viscosity oils, and that may get you by for a little while. In the meantime, drive it like you're 78 and wondering where your Volvo went......

[pasken]

Do you think I can try Lucas Pure Synthetic Oil Stabilizer? or it's better to use some other additive? Or change oil again this time to 20W50? Seems like I ll need to trade it in in the next couple months...

[JCL]

What do you hope to gain with an additive? It won't fix anything. It may make the oil thick enough to sell the vehicle quickly to an unsuspecting buyer.

Oil pressure rises with rpm. At low rpm you naturally have low pressure and the engine condition is making it worse. Fix it, live with it, or sell it.

[_XS3C_]

Originally Posted by pasken

.............. Never noticed anything similar on other cars..

I keep the oil level on my cars between MED and MAX [cold engine check only ] ..... but on the X5's it is way hard to find the correct oil level on the dipstick.
The oil level is by ANGLE and regardless of the correct amount oil in the engine [7.900mll], will be showing lower on the dipstick by 1/2 ...... [1L is between min and max]-- it have to be overfilled [by 'round 400mll] in order to get CLOSE to the max on the dipstick .....
Never had "problems" with the dipstick reading on any other cars if compared to the X's .....

[JCL]

Originally Posted by _XS3C_

I keep the oil level on my cars between MED and MAX [cold engine check only ] ..... but on the X5's it is way hard to find the correct oil level on the dipstick.

...Never had "problems" with the dipstick reading on any other cars if compared to the X's .....

You will get more consistent readings if you check the oil as BMW designed the procedure. From the manual...

1. Vehicle level
2. Engine at operating temperature, switched off
3. wait 5 minutes for the oil to drain down
4. Check the oil by inserting the dipstick completely

I got very consistent readings this way. The engine just wasn't designed to be checked cold, or right after shutting it off, and the relatively large quantity of oil in the sump makes it even more variable if the above isn't followed, in my experience.