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Discussion Starter #1
So, I might just be totally measuring this stuff wrong, or somehow overfilled with oil initially.. but here's the situation.

Did an oil change. Ran the engine, found it to be low, filled 0.75L thereabouts to get it to the top of the dipstick. It's been reading full (doesn't push above the second notch) for about 2 weeks now.

Suddenly, overnight, it's reading at about 25% from the bottom when hot. About 50% up from the notch when cold. I don't recall big blue plumes behind me. And I'm not seeing any major leaks. Bottom of the oil pan is nice and clean still, having had a new seal put in when I did the last change.

Any explanation for this? I am somewhat paranoid that I overfilled despite no solid dipstick reading confirming this.
 

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FWIW, the BMW specified way to check the oil is to let the car come up to full operating temp, shut off, check oil after 30 seconds. Does it make a difference from when cold? Not on my whip.
 

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Discussion Starter #3
FWIW, the BMW specified way to check the oil is to let the car come up to full operating temp, shut off, check oil after 30 seconds. Does it make a difference from when cold? Not on my whip.
Oh I did not realize that.. I actually have a notice ON my dipstick itself instructing to run for 15 seconds and then check. My concern is more around how it nearly always read entirely full in most conditions and only recently dropped to the 25-75 mark depending on temperature.
 

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Beyond measuring correctly with the method in the manual (page 115), form a habit of making your observations with consistency (e.g. while filling up gas, or after coming home from work).

Thereafter, if your engine is not leaking (other places to look: oil cap, grommets, valve cover gaskets), and is only a few weeks into a fresh oil change, and is still consuming oil, then read the board for explanations such as: type of oil, piston ring blow-by, effects of driving style.
 

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Discussion Starter #5 (Edited)
Beyond measuring correctly with the method in the manual (page 115), form a habit of making your observations with consistency (e.g. while filling up gas, or after coming home from work).

Thereafter, if your engine is not leaking (other places to look: oil cap, grommets, valve cover gaskets), and is only a few weeks into a fresh oil change, and is still consuming oil, then read the board for explanations such as: type of oil, piston ring blow-by, effects of driving style.
Thanks. Finding good information has been difficult. My driving style is unchanged. I switch the PO's oil to Lubrimoly 10W60. Other than that, I will need to investigate piston ring blow by.I'll take it for a compression test. I just replaced CCVs as well as a precaution. What's got me scratching my head is that, I check that oil almost daily, and it was basically overnight that it wasn't at full for once.
 

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Oil use will accelerate as the oil becomes worn (sheared). A 10-60 shears down pretty quickly...not THAT dramatically, but combined with your variability in measuring it could cause that perception...
 

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Oil use will accelerate as the oil becomes worn (sheared). A 10-60 shears down pretty quickly...not THAT dramatically, but combined with your variability in measuring it could cause that perception...
I recently experienced this in mine. I run the correct 5w-30, at just over 5000 miles on the oil it suddenly dropped it's level very quickly, about a quart. After changing the oil the level now is staying stable again.
 

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C'mon now. Oil consumption can't change overnight unless you develop an obvious leak.
So my suggestion is the anti-drain back valve in the oil filter housing.
 

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Oil use will accelerate as the oil becomes worn (sheared). A 10-60 shears down pretty quickly...not THAT dramatically, but combined with your variability in measuring it could cause that perception...

Excellent! I've noticed that after I first change my oil (TWS) I can go over 3K miles before I get to the ¼ way point up from the lower mark on the dip stick which is when I top up. This mileage gets shorter second time around before I've burnt back down to the ¼ way point again. I've noticed this in other cars too, but not to the extent of the M5 & TWS combo.

I've also noticed that somewhere around the ¾ point on the dip stick the oil drops more rapidly below this. I'm guessing due to there being a larger volume of oil higher up in the sump/block stiffener/block.

OP, you may want to just try being consistent with oil level checks. I always check mine after a good run with the engine up to full operating temperature. (usually after my 35 mile trip home from work) Let idle for 15-20 secs per the sticker and then check it a minute or 2 after you shut off the engine.
 

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Discussion Starter #10
C'mon now. Oil consumption can't change overnight unless you develop an obvious leak.
So my suggestion is the anti-drain back valve in the oil filter housing.
I'm not familiar with this. How does that manifest? I've scoured the engine bay for leaks including with the tray off. Looks good. I'm getting very minor oil deposition around the filler cap which I understand is par for the course with old caps. But we are talking minuscule amounts.

Maybe I am going nuts and it is just a consistency thing. I'm going to try to scientifically accurate for a while.
 

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I've taken a deep breath and a step back. :)
Assuming you did use a lot of oil in a short period, I can see some less obvious possibilities:
- the oil filter housing has a built-in non-return valve that stops the oil in the housing from draining back into the sump when the engine shuts down. If it leaks and you check oil level after the engine is shut down, this can yield falsely high readings. If you check the oil with the engine running, this is not the problem.
- the valve cover gaskets on both banks can leak oil into the spark plug wells and the oil can get sucked down the plug threads into the combustion chambers. That surprises me, but it's happened, according to some threads on here.
- the two outlet VANOS solenoids on the bank 2 side can leak so much oil that the drain passage back to the oil sump can't cope and the oil backs up into the plenum. Some of this gets sucked into the intakes and some drains back down the intake tubes into the air filters. Check the air filters.
- the two oil separators get too dirty and stop separating out the oil so it can drain back to the sump. So it gets sucked into the plenum like above. Or the separator drain line gets plugged. Again, check the air filters and air tubes for oil.
 

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Discussion Starter #12
That's a pretty definitive list there. I can definitely eliminate most of it based on work I've done recently. The oil filter housing leak is kind of funny. I need to investigate that since it does seem realistic for how odd the readings have been.
 

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Discussion Starter #13
I've taken a deep breath and a step back. :)
Assuming you did use a lot of oil in a short period, I can see some less obvious possibilities:
- the oil filter housing has a built-in non-return valve that stops the oil in the housing from draining back into the sump when the engine shuts down. If it leaks and you check oil level after the engine is shut down, this can yield falsely high readings. If you check the oil with the engine running, this is not the problem.
- the valve cover gaskets on both banks can leak oil into the spark plug wells and the oil can get sucked down the plug threads into the combustion chambers. That surprises me, but it's happened, according to some threads on here.
- the two outlet VANOS solenoids on the bank 2 side can leak so much oil that the drain passage back to the oil sump can't cope and the oil backs up into the plenum. Some of this gets sucked into the intakes and some drains back down the intake tubes into the air filters. Check the air filters.
- the two oil separators get too dirty and stop separating out the oil so it can drain back to the sump. So it gets sucked into the plenum like above. Or the separator drain line gets plugged. Again, check the air filters and air tubes for oil.

Alright so I'm thinking the previously mentioned oil filter housing leak might be the issue. Do you have an idea of timelines typically? I measured my oil at 10 minute intervals since shutting down the hot engine. The level steadily rises until it finally is cold and meets the high level line.

The BMW procedure as per the sticker and the dipstick is to measure when the engine is cold, after a 15 second idle. Doing this yields a pretty grim reading of very low (first notch).

So I have no idea what's going on here, unless maybe there is some flowback issues with the filter housing.
 

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Alright so I'm thinking the previously mentioned oil filter housing leak might be the issue. Do you have an idea of timelines typically? I measured my oil at 10 minute intervals since shutting down the hot engine. The level steadily rises until it finally is cold and meets the high level line.

The BMW procedure as per the sticker and the dipstick is to measure when the engine is cold, after a 15 second idle. Doing this yields a pretty grim reading of very low (first notch).

So I have no idea what's going on here, unless maybe there is some flowback issues with the filter housing.

Read it again. Operating temp, 15 second idle, shut off, wait 60 seconds, check level. It should be checked this way every time for consistent readings.
 

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I've found no significant difference on the level mark between stone cold, hot, waiting 60 seconds or 60 minutes etc.

The 330Ci I had seemed to be much more fussy.
 

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Alright so I'm thinking the previously mentioned oil filter housing leak might be the issue. Do you have an idea of timelines typically? I measured my oil at 10 minute intervals since shutting down the hot engine. The level steadily rises until it finally is cold and meets the high level line.
If I understand you correctly, that sure sounds like a leaking anti-drainback valve.

The valve is is opened by a spring and kept closed by the filter element. It's the one on the right in the pic. It pops up when you remove the filter and quickly drains the housing back to the sump.

How long does the oil pressure light (the red oil can one) on the dash stay on when you start the car after sitting overnight? It should go out immediately on engine start. If it is delayed a second or too (just like after an oil change), that also indicates the housing is draining down. There's 0.5 to 1 litre of oil in the housing.

DSC00208.JPG
 

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Discussion Starter #17
If I understand you correctly, that sure sounds like a leaking anti-drainback valve.

The valve is is opened by a spring and kept closed by the filter element. It's the one on the right in the pic. It pops up when you remove the filter and quickly drains the housing back to the sump.

How long does the oil pressure light (the red oil can one) on the dash stay on when you start the car after sitting overnight? It should go out immediately on engine start. If it is delayed a second or too (just like after an oil change), that also indicates the housing is draining down. There's 0.5 to 1 litre of oil in the housing.

View attachment 439330
Ah very helpful, thanks. So, actually, I have never even noticed the oil pressure light. It would go off immediately. Even after an oil change, it never stayed on. Seems to me that it could still be the valve, however. Seems like not too bad of a fix. Figure the spring goes first?
 

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I don't know how it would fail open. The valve plug cocked on the seat seems likely. RealOEM doesn't show it separately so you would have to buy a new housing.

To make sure that is the problem, you could remove the filter, hold the valve down (closed) with a screwdriver, pour in some oil, and watch for it draining.
 
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