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Old 03-26-2020, 08:53 AM   #1
sefeing
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Seeping oil level sensor - change whole sensor or just o-ring?

When I had my support plate off a few weeks back, I took the time to check for any leaks on my 89k mile 2002 325i. Pan + gasket looked fine, but I noticed what must be a long time weep / very very small leak from the sensor (can very much tell where). Looks more like a weep than a leak, since it wasn't actively dripping or anything, but I figure I may as well replace it at my next oil change. From what I can tell, the car needs an extra 1/2 - 3/4 liter every 3k(ish) miles, so really minor leak, and the engine is barely burning, which is great.

My question - should I purchase the whole sensor to replace, or just the O-ring?
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Old 03-26-2020, 10:49 AM   #2
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No reason to replace it if it's working! They last a long time, so I'd just reseal it.

Because, really, it's almost trivial to do at an oil change.

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Old 03-26-2020, 10:56 AM   #3
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No reason to replace it if it's working! They last a long time, so I'd just reseal it.

Because, really, it's almost trivial to do at an oil change.

t
Fair point! didn't know if they have a tendency to break after time when removing , and if it was more worth it to have the whole sensor on hand. But sounds good!

Bummer I'll have to take the reinforcement plate off again, but not terrible.
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Old 03-27-2020, 07:34 AM   #4
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Yeah, those sensors tend to go bad after 80k miles or so. The symptom is the yellow (not red!) oil light will come on for several seconds after you shut off the engine. The sensor is made by Hella and can be bought on Amazon. It’ll take you maybe 10 minutes to change it as you car doesn’t (shouldn’t ?) have the aluminum chassis re-enforcement panel that the 330’s have.
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Old 03-27-2020, 08:27 AM   #5
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Originally Posted by markusmarkus View Post
Yeah, those sensors tend to go bad after 80k miles or so. The symptom is the yellow (not red!) oil light will come on for several seconds after you shut off the engine. The sensor is made by Hella and can be bought on Amazon. It’ll take you maybe 10 minutes to change it as you car doesn’t (shouldn’t ?) have the aluminum chassis re-enforcement panel that the 330’s have.
Gotcha, so maybe worth just replacing it preemptively then, since I'm at 89k?

I think it was by the years. My 2002 325i has the aluminum plate (8 non-reusable bolts)
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Old 03-27-2020, 10:38 AM   #6
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Originally Posted by markusmarkus View Post
Yeah, those sensors tend to go bad after 80k miles or so. The symptom is the yellow (not red!) oil light will come on for several seconds after you shut off the engine. The sensor is made by Hella and can be bought on Amazon. It'll take you maybe 10 minutes to change it as you car doesn't (shouldn't ?) have the aluminum chassis re-enforcement panel that the 330's have.
I've seen several of those oil level sensors go bad and simply be silent: no yellow warning light, no low oil indicator on dashboard, nada...so beware and don't rely on the darn thing.

FWIW, the 325 and 330 have the same reinforcement plate. You're maybe thinking of the earlier (pre 02/2001?) totally tubular reinforcement structure.
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Old 03-27-2020, 10:56 AM   #7
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Originally Posted by markusmarkus View Post
Yeah, those sensors tend to go bad after 80k miles or so. The symptom is the yellow (not red!) oil light will come on for several seconds after you shut off the engine. The sensor is made by Hella and can be bought on Amazon. It’ll take you maybe 10 minutes to change it as you car doesn’t (shouldn’t ?) have the aluminum chassis re-enforcement panel that the 330’s have.
When it is functioning properly, it will behave as you have described.
When Faulty, the yellow oil lamp will come on for about 15 seconds a few seconds after start-up.
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Old 03-27-2020, 11:05 AM   #8
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I would replace. They're cheap and have a history of going bad. And it you have the reinforcement plate that covers the pan variety I would definitely replace the whole thing vs just the o-ring. Since you're going through the trouble.
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Old 03-27-2020, 11:15 AM   #9
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They're cheap...
HELLA $55 https://www.amazon.com/dp/B000VUANRE/
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Old 03-27-2020, 12:05 PM   #10
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Love it! I'll grab one from FCPEuro when I order my next round of parts / oil change. Easy enough. I'm pretty diligent about monitoring & checking my oil so not too worried until then!
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Old 03-27-2020, 12:07 PM   #11
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The prices are higher right now, but the aftermarket sensors used to be under $10 on FleaBay. The last one I bought was $7.29. That's less than the price of a replacement gasket alone. That gives you the option of using just the new gasket, with a back-up plan of using the whole sensor if you find that original sensor body was leaking.

If you are reusing the original sensor, make certain that oil can flow through from the hole at the tip to the base.

This is a molded gasket. It gets no gasket sealer. The only ones I've seen with significant leaks were gooped with gasket maker. That probably worked initially, but it was forming drops a few years later. Gasket maker is used only when the surfaces are so bad that you've given up on the seal working properly.

In my experience, the aftermarket sensors are physically well made and fit like the originals. I slightly prefer still-working original ones, but they don't have that much of a reliability advantage.

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