What are these black plastic caps on the trans and why are they leaking?? [PICS]
Thread Starter
Junior Member
Joined: Mar 2007
Posts: 70
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From: Germantown, TN
2005 C55
What are these black plastic caps on the trans and why are they leaking?? [PICS]
This all started because upon checking the oil level, my computer told me to add 2 qts of oil, which I thought was very unusual. I had topped it off about 1000 miles ago with 2 qts...again, what my computer told me to add (that time, I actually got a notice to add oil).
**mini rant**Why didn't they put a damn dipstick on this car!?**/end**
So I decided it was time for me to do my first oil change on this thing (since buying the car in March), start fresh and see if this thing is actually leaking/burning oil.
Anyway, I'm under there and notice these two black plastic caps on the trans bell housing and they had oil around the edges. There was also a small amount of oil on the O2 sensor wires and there was lots of gunk on the plastic undertray (which I went ahead and cleaned off).
What are these? And do you think it's possible to leak/burn up that much oil in 1000 miles?? Seems VEEEERY odd...and not in a good way.
**mini rant**Why didn't they put a damn dipstick on this car!?**/end**
So I decided it was time for me to do my first oil change on this thing (since buying the car in March), start fresh and see if this thing is actually leaking/burning oil.
Anyway, I'm under there and notice these two black plastic caps on the trans bell housing and they had oil around the edges. There was also a small amount of oil on the O2 sensor wires and there was lots of gunk on the plastic undertray (which I went ahead and cleaned off).
What are these? And do you think it's possible to leak/burn up that much oil in 1000 miles?? Seems VEEEERY odd...and not in a good way.
Thread Starter
Junior Member
Joined: Mar 2007
Posts: 70
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From: Germantown, TN
2005 C55
For the record, I've never seen a single drop of oil underneath the car...granted, it's largely covered by the plastic trays...but I think it'd be quite apparent that 2 quarts of oil had leaked out. Obviously some had, based on the gunk all over the tray...but not 2 quarts.
So another question...does the oil sensor ever go bad?? Why wouldn't the car notify me to add oil if it was down 2 quarts????
So another question...does the oil sensor ever go bad?? Why wouldn't the car notify me to add oil if it was down 2 quarts????
Senior Member
Joined: Apr 2007
Posts: 458
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From: Norcal/Socal
C63 E63
Those two black caps covers the opens to the torque converter. Usually in most cases when those are wet/leaking, it's coming from the rear main seal. There have been cases which the front pump of the transmission leaks and it will be in that area as well. Check your valve covers as well, make sure they're not leaking too
MBWorld Fanatic!
Joined: Mar 2007
Posts: 1,948
Likes: 3
From: Houston, TX
C32/C55 AMG
Be careful not to over fill your engine with oil and yes the oil sensors can be faulty. Trying putting your car in dyno mode to get a better oil reading. I have the same dreaded rear main seal, but it leaked 2 quarts over 3k miles.
Last edited by loudandheard; Sep 1, 2011 at 09:09 AM.
Senior Member
Joined: May 2011
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C55 AMG, E55 AMG
Yep, could be a rear main seal leak. If it is, what sucks about it is that the seal itself is just loose change, but dealerships will gladly quote you 2K to 3K+ for labor since they have to pull down the trans. Good thing I live near Speedriven and they only charged me a fraction for the same quality of work.
I would also take this opportunity to do a tranny flush (if you haven't done it yet before).
I would also take this opportunity to do a tranny flush (if you haven't done it yet before).
Senior Member
Joined: May 2010
Posts: 333
Likes: 1
C63, C55 (Sold)
That actually happened to me on the last oil change: For some reason, the computer displayed that the engine had an over fill. Weird, since I used as much oil as on a prior oil change. I had to purge a little to put it back to normal.
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Thread Starter
Junior Member
Joined: Mar 2007
Posts: 70
Likes: 0
From: Germantown, TN
2005 C55
Those two black caps covers the opens to the torque converter. Usually in most cases when those are wet/leaking, it's coming from the rear main seal. There have been cases which the front pump of the transmission leaks and it will be in that area as well. Check your valve covers as well, make sure they're not leaking too
Yep, could be a rear main seal leak. If it is, what sucks about it is that the seal itself is just loose change, but dealerships will gladly quote you 2K to 3K+ for labor since they have to pull down the trans. Good thing I live near Speedriven and they only charged me a fraction for the same quality of work.
I would also take this opportunity to do a tranny flush (if you haven't done it yet before).
I would also take this opportunity to do a tranny flush (if you haven't done it yet before).
Good idea about the trans flush.
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MBWorld Fanatic!
Joined: Mar 2007
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From: Houston, TX
C32/C55 AMG
If you want to check to see if your vehicle is measuring your oil correctly, you can check it during your oil change. I put the car in dyno mode and it allows me to check how many liters of oil the car has. I use an oil extractor that has measurement on it to remove the oil. When I'm done, I compare the two measurement to see if the car is reading the oil level correctly. This will also give you better piece of mind that you are not overfilling. The bs readout on the tach will only tell you that your service is due or that you are on time. I was almost two quarts low and it was reading that every thing was fine. I really recommend using dyno mode to get a more accurate reading.
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From: Houston, TX
C32/C55 AMG
Thread Starter
Junior Member
Joined: Mar 2007
Posts: 70
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From: Germantown, TN
2005 C55
If you want to check to see if your vehicle is measuring your oil correctly, you can check it during your oil change. I put the car in dyno mode and it allows me to check how many liters of oil the car has. I use an oil extractor that has measurement on it to remove the oil. When I'm done, I compare the two measurement to see if the car is reading the oil level correctly. This will also give you better piece of mind that you are not overfilling. The bs readout on the tach will only tell you that your service is due or that you are on time. I was almost two quarts low and it was reading that every thing was fine. I really recommend using dyno mode to get a more accurate reading.
With this last oil change, I drained from the pan (both bolts) and the engine took 9 quarts to refill. Put in 7...car said add 1....added and then started up, let it run up to operating temp, shut down and checked after 5 mins...said add 1 quart. Added and it said it was level. As of today, engine oil level is still ok. I'm going to monitor it very closely now and will give this dyno mode thing a whirl.
Thread Starter
Junior Member
Joined: Mar 2007
Posts: 70
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From: Germantown, TN
2005 C55
Just thought I would update you guys...
Took it to the dealership to have them inspect for a leak. They went in there with some little camera and found that the rear main seal did appear to be leaking ever so slightly, BUT they actually advised that I not replace it given that it was so minor and the costs associated with it. They told me to just monitor my oil loss closely. 500 miles on from my oil change and I'm happy to report it's still level! For those curious, the cost to replace the RMS was ~$1,300 (tax & all) from the dealership, which actually is a lot better than I was expecting.
Took it to the dealership to have them inspect for a leak. They went in there with some little camera and found that the rear main seal did appear to be leaking ever so slightly, BUT they actually advised that I not replace it given that it was so minor and the costs associated with it. They told me to just monitor my oil loss closely. 500 miles on from my oil change and I'm happy to report it's still level! For those curious, the cost to replace the RMS was ~$1,300 (tax & all) from the dealership, which actually is a lot better than I was expecting.
