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      04-14-2021, 02:35 PM   #1
Quickbricky
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Possible rear main seal?

Hi all I’m a new owner of a 2018 440i B58. My Indy garage noticed slight sweat oil present on engine/gearbox. Having a look online seems to be pointing to rear main seal but again I’m no expert and garage said further investigation would be required. I’m asking if anyone can tell with this picture? Thanks in advance
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      04-14-2021, 03:59 PM   #2
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Oil is super tough to diagnose unless you put the UV marker in it, and check for fresh leaks.

The air from driving, fan, etc. makes oil wick in wild and crazy ways, often ending in places far from where it started.
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      04-14-2021, 05:08 PM   #3
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Yeah, picture is also very close up. Basically you trace the oil forward and upwards from where it is to see where it leads... but your best bet is cleaning everything off, adding a tracer, and finding the leak when you have fresh oil.

That could easily be oil pan gasket, or something further up.
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      04-14-2021, 06:07 PM   #4
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I should add that you can just spray that with engine cleaner, and pressure wash at the car wash wand wash to clean it. Amazon has kits that have the dye and UV flashlight for cheap (I know, did it on my truck).

This is what I bought:
Flashlight:
https://www.amazon.ca/gp/product/B00...?ie=UTF8&psc=1
Dye:
https://www.amazon.ca/gp/product/B00...?ie=UTF8&psc=1

Looks like the that dye isn't in stock, but it gives you the idea. In Canadian $, the flashlight was $17, the dye, $38.

I'd "waste" the money on that route vs heading to the shop. They are basically going to do the exact same thing, but you get the luxury of paying shop rates on top of it.
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      05-14-2021, 10:20 AM   #5
Quickbricky
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Cleaned the area and coming back again the oil looks fairly light in colour maybe gearbox oil on the seal which joins the engine?
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      05-14-2021, 01:19 PM   #6
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Quote:
Originally Posted by Quickbricky View Post
Cleaned the area and coming back again the oil looks fairly light in colour maybe gearbox oil on the seal which joins the engine?
You can try adding one of the dyes to your engine oil, clean it, and when it leaks again check if it reacts to the UV. That would confirm whether its engine or gearbox oil.
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      05-16-2021, 06:38 AM   #7
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...and before you get convinced by the shop that you have to fix this leak and spend thousands doing so...you can just keep a sheet of cardboard under the car and replace oil as needed...and you wouldn't be such a horrible bmw owner.

Rear main seal is probably among the most expensive leaks to fix...I lived with one in my e46 for years waiting for my clutch to fail so I could fix both at the same time. Clutch lasted nearly 400k miles...so I never fixed the leak!
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      05-16-2021, 02:06 PM   #8
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Quote:
Originally Posted by dmaxdmax View Post
...and before you get convinced by the shop that you have to fix this leak and spend thousands doing so...you can just keep a sheet of cardboard under the car and replace oil as needed...and you wouldn't be such a horrible bmw owner.

Rear main seal is probably among the most expensive leaks to fix...I lived with one in my e46 for years waiting for my clutch to fail so I could fix both at the same time. Clutch lasted nearly 400k miles...so I never fixed the leak!
This is correct. Oil leaks aren't a problem unless the level is dropping significantly between changes. If it's an easy fix, sure, do it. But a rear main seal? Just let it leak and clean it up every once and while. The only ones I've bothered with on the E46 were OFHG and VCG. I let the pan leak because it was just a ton of work to replace. The E82 also had a pan leak. Ignored.
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