Please help - 2012 ML350 Bluetec Oil Leak
01-24-2019, 08:09 AM
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2012 ML350 Bluetec
Please help - 2012 ML350 Bluetec Oil Leak
Hey guys, I recently purchased a 2012 ML350 Bluetec. Vehicle has 178,000km on it. However, there is an oil leak and I’m trying to figure out the source. The leak is leaving stains on the driveway and upon removing the cover, I noticed the small oil pan (with the drain plug for oil change) soaked in oil. Is the leak from that small oil pan itself or is it most likely from above? If from above, does anyone know what it could be that drains past that oil pan? I’ve heard of engine oil cooler seals being a common issue with these vehicles. When the engine oil cooler seal leaks, does it drip down that way? Any information and/or insight would be great.
Cheers.
01-24-2019, 11:20 AM
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i havent had the issue so cant help regarding the seal leak, but i think from most of what i have read the advice you may first get is to clean the engine bay of the oil. then after it is clean monitor it and that should help you identify easier where the leak is coming from, or else were all just making random guesses.
that seal is definitely one spot
someone here posted photos once and had oil i think it was in the air ducts, but that leak actually came from the seal problem. i think it was a turbo seal
that seal is definitely one spot
someone here posted photos once and had oil i think it was in the air ducts, but that leak actually came from the seal problem. i think it was a turbo seal
01-24-2019, 11:22 AM
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You won't know for sure 'till you thoroughly blast the whole area clean and then keep a close eye on it. If the leak is coming from the rear of the engine, it's a good chance it's the oil cooler seals. If from the front, could be as simple as the oil filter housing gasket.
Start by cleaning it...
Start by cleaning it...
01-24-2019, 12:35 PM
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is it safe to just power wash/car wash under the hood just blasting all whilly nilly everywhere?
i wanted to do that once to clean the engine bay up and make it look all nice, but was paranoid i would get water in places i shouldnt, and break or damage something. Or clean oil off something that should be oiled and then have rust or other problems.
i wanted to do that once to clean the engine bay up and make it look all nice, but was paranoid i would get water in places i shouldnt, and break or damage something. Or clean oil off something that should be oiled and then have rust or other problems.
01-24-2019, 01:23 PM
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is it safe to just power wash/car wash under the hood just blasting all whilly nilly everywhere?
i wanted to do that once to clean the engine bay up and make it look all nice, but was paranoid i would get water in places i shouldnt, and break or damage something. Or clean oil off something that should be oiled and then have rust or other problems.
i wanted to do that once to clean the engine bay up and make it look all nice, but was paranoid i would get water in places i shouldnt, and break or damage something. Or clean oil off something that should be oiled and then have rust or other problems.
01-24-2019, 01:31 PM
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Thanks guys for the input. I’ve cleaned the bottom of the oil pan as suggested. If it’s the oil cooler seal, where exactly should I be looking for the leak? How does the oil cooler seals leak from the back of the engine? I called a mechanic and he suggested rear main engine seal which requires the transmission to be dropped - is that even a common leak for these vehicles?
Cheers
Cheers
01-24-2019, 04:45 PM
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You won't know for sure 'till you thoroughly blast the whole area clean and then keep a close eye on it.
If the leak is coming from the rear of the engine, it's a good chance it's the oil cooler seals. If from the front, could be as simple as the oil filter housing gasket.
Start by cleaning it...
If the leak is coming from the rear of the engine, it's a good chance it's the oil cooler seals. If from the front, could be as simple as the oil filter housing gasket.
Start by cleaning it...
It runs down the rear of the engine valley and down the bellhousing
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01-24-2019, 05:12 PM
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cooler seal actually leak? The under belly cover was covered in oil when I removed it so I assume all that oil must’ve dripped between now and the last oil change?
01-25-2019, 05:25 AM
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That surely depends on how badly the seals are leaking. And maybe the seals aren't leaking. Is it possible that the pan plug or oil level sender is the culprit?
Next time you check, look to see if the pan is wet higher up on its sides. If the oil is only on the bottom, you may very well simply have or had a leaky drain plug or sender gasket.
Next time you check, look to see if the pan is wet higher up on its sides. If the oil is only on the bottom, you may very well simply have or had a leaky drain plug or sender gasket.
02-20-2019, 07:57 AM
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2012 ML350 Bluetec
That surely depends on how badly the seals are leaking. And maybe the seals aren't leaking. Is it possible that the pan plug or oil level sender is the culprit?
Next time you check, look to see if the pan is wet higher up on its sides. If the oil is only on the bottom, you may very well simply have or had a leaky drain plug or sender gasket.
Next time you check, look to see if the pan is wet higher up on its sides. If the oil is only on the bottom, you may very well simply have or had a leaky drain plug or sender gasket.
02-20-2019, 11:27 AM
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Thanks Peter - I recently just noticed it leaking again so definitely wasn’t the oil pan that I resealed. If it is the engine oil cooler seal, how do I differentiate the leak from that versus the leak from the rear main seals? Is the oil level sender known to leak because I never replaced that when I resealed the oil pan.
If you are having a hard time tracking it down, might want to try a leak detection dye and uv flashlight, something like this:
Last edited by johnand; 02-20-2019 at 11:30 AM.
02-20-2019, 11:31 AM
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Thanks John - I’m not super car savvy so sorry if this question sounds dumb but is the o-ring part of the oil level sender? Should I try replacing the oil level sender first and driving it to see if the leak persists?
02-20-2019, 11:44 AM
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Dan, I believe the oil sender in the pan has either an o-ring seal, or a copper crush seal, and you should be able to replace just that. It is more likely the seal, than the sender itself leaking, but don't rule that out. If the sender is reasonably priced, then I would just replace the whole thing. I would look it up to be sure, but my EPC is just a few months too old to cover my ML350, so I planned on checking with my dealer this week, or trying to research it online.
02-20-2019, 11:58 AM
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Dan, I believe the oil sender in the pan has either an o-ring seal, or a copper crush seal, and you should be able to replace just that. It is more likely the seal, than the sender itself leaking, but don't rule that out. If the sender is reasonably priced, then I would just replace the whole thing. I would look it up to be sure, but my EPC is just a few months too old to cover my ML350, so I planned on checking with my dealer this week, or trying to research it online.
what I’ve read, the rear engine seal leak manifests the same way as an engine oil cooler seal leak. Would hate to have to do any unnecessary work.
02-20-2019, 01:46 PM
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That’s good to know John - thank you for your help. I’m taking it in today to my mechanic so let’s see what he thinks it is. I just hope he doesn’t misdiagnose it if it is the engine oil cooler seal leaking because from
what I’ve read, the rear engine seal leak manifests the same way as an engine oil cooler seal leak. Would hate to have to do any unnecessary work.
Anyway, a quick cursory check online, and that sensor in the pan, it the oil temperature sensor, and it relatively cheap to replace, and as you can see on the link, it has a separate seal as well. https://www.idparts.com/oil-temperat...2-p-10355.html . I will try and get part numbers.
02-20-2019, 02:14 PM
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Dan, yeah I hear you on the oil cooler leak issue. Definitely don't want to do that unless you are 110% sure that is the leak. That is a major surgery to replace those seals.
Anyway, a quick cursory check online, and that sensor in the pan, it the oil temperature sensor, and it relatively cheap to replace, and as you can see on the link, it has a separate seal as well. https://www.idparts.com/oil-temperat...2-p-10355.html . I will try and get part numbers.
Anyway, a quick cursory check online, and that sensor in the pan, it the oil temperature sensor, and it relatively cheap to replace, and as you can see on the link, it has a separate seal as well. https://www.idparts.com/oil-temperat...2-p-10355.html . I will try and get part numbers.
appears to be just above the oil pan (oil
pan is clean). If it is the engine cooler seal leak, should the transmission housing be wet?
02-20-2019, 03:34 PM
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If the oil cooler is leaking, the oil drips out the back side of the block and down. It'll be a beotch to confirm though
02-20-2019, 03:38 PM
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Yessir. Just confirmed that the if the oil cooler seals are leaking, it does in fact drip THROUGH the transmission bell housing which can present itself with the same symptoms of a rear main engine seal leak. Don’t think the rear main engine seal leak is a common issue with these vehicles so my bet is that it’s the engine oil cooler seals.
02-20-2019, 04:09 PM
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My Leak
Here are a few pics of my leak. How does it compare to yours Dan? After closer inspection, look at the pic of the bellhousing to the left of DPF. That sure looks like oil leaking down, so I may have the oil cooler seals leak.
02-21-2019, 04:57 AM
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John, how many miles do you have on yours?
EDIT, just saw the mileage in your sig. 44k miles is not a lot of mileage for your seals to be leaking. Damn!!!
This ongoing saga with the oil seals is incredible. At least one revision to Viton (purple) seals, if not two. From what I understand, it's got to be the under-hood heat which is the culprit.
If this indeed correct, then losing the belly pan and engine cover should indeed help. I've done both and it's the wifey's daily driver. She's almost never stuck in traffic, so that should help as well. Also, we got the truck at 20k km and I did the mods by 30k, so hopefully the seals haven't been subjected to that much heat.
Only time will tell if I'm full of crap though...
EDIT, just saw the mileage in your sig. 44k miles is not a lot of mileage for your seals to be leaking. Damn!!!
This ongoing saga with the oil seals is incredible. At least one revision to Viton (purple) seals, if not two. From what I understand, it's got to be the under-hood heat which is the culprit.
If this indeed correct, then losing the belly pan and engine cover should indeed help. I've done both and it's the wifey's daily driver. She's almost never stuck in traffic, so that should help as well. Also, we got the truck at 20k km and I did the mods by 30k, so hopefully the seals haven't been subjected to that much heat.
Only time will tell if I'm full of crap though...
02-21-2019, 09:01 AM
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John, how many miles do you have on yours?
EDIT, just saw the mileage in your sig. 44k miles is not a lot of mileage for your seals to be leaking. Damn!!!
This ongoing saga with the oil seals is incredible. At least one revision to Viton (purple) seals, if not two. From what I understand, it's got to be the under-hood heat which is the culprit.
If this indeed correct, then losing the belly pan and engine cover should indeed help. I've done both and it's the wifey's daily driver. She's almost never stuck in traffic, so that should help as well. Also, we got the truck at 20k km and I did the mods by 30k, so hopefully the seals haven't been subjected to that much heat.
Only time will tell if I'm full of crap though...
EDIT, just saw the mileage in your sig. 44k miles is not a lot of mileage for your seals to be leaking. Damn!!!
This ongoing saga with the oil seals is incredible. At least one revision to Viton (purple) seals, if not two. From what I understand, it's got to be the under-hood heat which is the culprit.
If this indeed correct, then losing the belly pan and engine cover should indeed help. I've done both and it's the wifey's daily driver. She's almost never stuck in traffic, so that should help as well. Also, we got the truck at 20k km and I did the mods by 30k, so hopefully the seals haven't been subjected to that much heat.
Only time will tell if I'm full of crap though...
If they ever crap out when I am out or warranty, I will find a way to fab up a relocation or the oil cooler.
02-21-2019, 04:30 PM
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I believe my leak was a lot worse than yours John - it was a lot messier and once they cleaned it with brake fluid, the mechanic had it on the hoist running for a bit and the oil was visibly leaking through the bellhousing and dripping down. What made you assume it was the oil sensor? Seems like yours might be leaking from the same area as mine by the looks of it unless the oil leaking from the oil sensor splashed backwards while driving?
02-22-2019, 11:31 PM
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Originally Posted by Dan8807
Thanks Peter - I recently just noticed it leaking again so definitely wasn’t the oil pan that I resealed. If it is the engine oil cooler seal, how do I differentiate the leak from that versus the leak from the rear main seals? Is the oil level sender known to leak because I never replaced that when I resealed the oil pan.
Im sure there are way more.
02-24-2019, 06:52 PM
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The most likely culprit are the oil cooler seals, and yes, the oil runs down the transmission bell housing. While the third revision of the seals - the first ones made from Viton - was introduced in 2011, MB was still using whatever old silicone-based 2nd gen seals they had in stock at various production plants well into 2013 (I've seen 2014 MY MLs with the old 2nd gen orange seals). The 3rd gen seals are less likely to fail but they still do. The fourth gen seals (also purple Viton but with a larger surface area) were introduced last year. Regardless of where you get this serviced, make sure you get the 4th gen purple seals... the aftermarket ones are even worse than the orange ones.
