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Discussion Starter · #1 ·
hello, this isn't my first time visiting this form page but will be my first time uploading, so sorry if this has already been answered or asked before. I own a 2004 325i and am having some trouble trying to figure out what's happening to my oil. On startup, I have no oil light and my level is correct on where it should be normal but after 30 mins of driving I turn my car off and the oil light comes on. I go and check the dipstick and it says I'm at the first notch??! After I let it sit for a while or overnight it goes back to the normal range. What could be causing this? I've never seen this happen before so I'm clueless. Could I not be topping the oil off correctly? Is the ccv bad? By the way, this is my first e46 but I have owned a 99 e36 328is before.

if someone can maybe help I would very much appreciate it!
 

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//Binary is in my DNA
2002 BMW 325i
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4,482 Posts
Your oil level sensor is going bad. Common problem. Just replace it next time you do an oil change. It's fairly cheap, <$50 but you will need to pull your reinforcement plate to get at it.
 

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E46 F10 W204 W212
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hello, this isn't my first time visiting this form page but will be my first time uploading, so sorry if this has already been answered or asked before. I own a 2004 325i and am having some trouble trying to figure out what's happening to my oil. On startup, I have no oil light and my level is correct on where it should be normal but after 30 mins of driving I turn my car off and the oil light comes on. I go and check the dipstick and it says I'm at the first notch??! After I let it sit for a while or overnight it goes back to the normal range. What could be causing this? I've never seen this happen before so I'm clueless. Could I not be topping the oil off correctly? Is the ccv bad? By the way, this is my first e46 but I have owned a 99 e36 328is before.

if someone can maybe help I would very much appreciate it!
All of that sounds normal. A light at shut off indicates low oil. A light after startup indicates a bad sensor.

As far as the actual oil level, it's low after shut off because all the oil is everywhere else in the engine. In the morning it's back in the sump. Again, sounds like normal operation to me. So go add some oil.
 

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2016 340i xD 6-spd
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...or you could have the wrong dipstick. I believe the poster above is correct...a bad sensor will display at start and then go off after 15 secs. or something (I forget).

If you show 'perfect' level in the a.m. on level ground, check the numbers on the oil dipstick fob. I had mine switched...always read 5/8ths quarts low....

Next oil change, drain it all, put in exactly what you need (6.9 qts.) and that's where your full mark should be on the dipstick...if not...make a new mark or get a correct dipstick.
 

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2001 325i Sedan
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Two more potential problems I almost NEVER see mentioned...

1) On the bottom of the plastic oil filter "holder", there are two small O-rings. When you remove the oil filter, you pull that holder out, which opens the port those O-rings seal up, allowing oil to drain out of the oil filter housing. This, in effect, ADDS a quart of oil to the sump. Many people, when they do an oil filter change, do NOT replace those O-rings. So, they leak. When you park the car, you can wait the recommended 5-10 minutes, check the oil level, and it will be up to the FULL mark. Come back a few hours later, and you will find the level is well ABOVE the FULL mark.

2) There is also a check valve on the underside of the oil filter head. It, too, exists to HOLD oil in the oil filter and a few other places, so the oiling system creates pressure much quicker on engine start. The poppet in that check valve will, over time, actually cut a slot in the seat of the check valve, creating a relatively huge leak.

In both cases, you can kinda judge whether there is a problem or not by checking oil level on a hot and cold engine, and by checking how long it takes the RED oil warning light to go out after the engine is started. The light should go out in no more than a second or so. If it takes longer, you surely have at least ONE of the above problems. I would suggest checking this after the car has been fully warmed up, then parked for perhaps an hour - long enough for the oil to leak down, but not so long that it gets cold. Check the oil level on the dipstick 5 minutes AFTER the hot engine is first shut down, then again just BEFORE re-starting it an hour later. Ideally, both reading should be nearly the same. If you see a big difference in oil level or the oil light takes several seconds to go out, then you have a problem.

If you check the oil WHILE the engine is running, or very shortly AFTER it is turned off, you WILL get a low reading. A running engine will typically give an oil dipstick reading at least two quarts below the FULL mark.

If I am reading the OP correctly, his car almost certainly has at least one of these problems.
 

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Discussion Starter · #7 ·
All of that sounds normal. A light at shut off indicates low oil. A light after startup indicates a bad sensor.

As far as the actual oil level, it's low after shut off because all the oil is everywhere else in the engine. In the morning it's back in the sump. Again, sounds like normal operation to me. So go add some oil.
I should also state that the light (yellow) only comes on after I turn the car off (and stays on for a bit after I get out of the car). It never comes on when the car is started. Now the red light does come on when I do start the car up but only for a second or two. Also, thanks to everyone for replying!
 

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Discussion Starter · #8 ·
Two more potential problems I almost NEVER see mentioned...

1) On the bottom of the plastic oil filter "holder", there are two small O-rings. When you remove the oil filter, you pull that holder out, which opens the port those O-rings seal up, allowing oil to drain out of the oil filter housing. This, in effect, ADDS a quart of oil to the sump. Many people, when they do an oil filter change, do NOT replace those O-rings. So, they leak. When you park the car, you can wait the recommended 5-10 minutes, check the oil level, and it will be up to the FULL mark. Come back a few hours later, and you will find the level is well ABOVE the FULL mark.

2) There is also a check valve on the underside of the oil filter head. It, too, exists to HOLD oil in the oil filter and a few other places, so the oiling system creates pressure much quicker on engine start. The poppet in that check valve will, over time, actually cut a slot in the seat of the check valve, creating a relatively huge leak.

In both cases, you can kinda judge whether there is a problem or not by checking oil level on a hot and cold engine, and by checking how long it takes the RED oil warning light to go out after the engine is started. The light should go out in no more than a second or so. If it takes longer, you surely have at least ONE of the above problems. I would suggest checking this after the car has been fully warmed up, then parked for perhaps an hour - long enough for the oil to leak down, but not so long that it gets cold. Check the oil level on the dipstick 5 minutes AFTER the hot engine is first shut down, then again just BEFORE re-starting it an hour later. Ideally, both reading should be nearly the same. If you see a big difference in oil level or the oil light takes several seconds to go out, then you have a problem.

If you check the oil WHILE the engine is running, or very shortly AFTER it is turned off, you WILL get a low reading. A running engine will typically give an oil dipstick reading at least two quarts below the FULL mark.

If I am reading the OP correctly, his car almost certainly has at least one of these problems.
It's never above the full mark but perfectly between the bottom notch and top notch. Then when I check oil around 10 mins after shut off it's right below the bottom notch on the dipstick. I took a photo of the dipstick after driving around (picture below. also those oil stains are from another car lmao) and now ill wait an hour and take another photo to post. I will also take a look at those two potential problems later this week to see if those will help out!
929509
 

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2001 325i Sedan
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Another thing to check - Shut off the engine. After an hour, or even a day, if you carefully unscrew and lift the oil filter cap, the reservoir should be full, VERY wet and dripping with oil. If not, those little O-rings on the bottom end of the filter holder NEED to be replaced.
 

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2005 330i manual transmission performance package
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It's never above the full mark but perfectly between the bottom notch and top notch. Then when I check oil around 10 mins after shut off it's right below the bottom notch on the dipstick. I took a photo of the dipstick after driving around (picture below. also those oil stains are from another car lmao) and now ill wait an hour and take another photo to post. I will also take a look at those two potential problems later this week to see if those will help out!
View attachment 929509
If that is the level ten minutes after shutting off the engine, on level ground, then your oil level sensor is reporting correctly that you need to add a quart.
During your next oil change you can replace the small O-rings on the oil filter plastic piece just because they are cheap, easy to do, and probably still original.
I wouldn't replace the oil level sensor untill you get either an intermittent yellow oil light shortly after startup, or a sensor-specific error code read by INPA or other BMW-specific diagnostic tools.
The replacement oil level sensors for sale today, even at the dealer, aren't the same quality as the original ones...
 

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//Binary is in my DNA
2002 BMW 325i
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4,482 Posts
I misspoke earlier. Here are the oil light conditions.
Red light: Low oil pressure. - If you see this at any time other than when the engine is not running or it just started about a second ago, shut your engine off immediately!

Yellow light on after engine shutdown: Oil less than 1 quart low. - Check oil level with dipstick and top off.

Yellow light on while driving: Oil 1 quart or more low. - Check oil level with dipstick and top off ASAP.

Yellow light on for 15 seconds after engine start: Oil level sensor fault. - Replace sensor at your next oil change and monitor oil level with dipstick in the mean time.
 
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