Hi all, I have just recently done an oil and filter change on my '16 C63S with 54,000 kms and ive filled it to just under the maximum level on the dipstick. After my first 300km drive after the oil change I noticed that my baby left a bit of a puddle on my garage floor.

After pulling all the undertrays off again it appears that the oil is seeping down from the rear of the engine/start of the trans and pooling on top of the oil pan bolt. Its 100% not the gasket or seal around the oil pan, ive cleaned everything off with brake clean and had the car started while I was under it and watched where the oil started coming from.

Is this a common thing with the M177? Im picking it might be the rear main seal on the engine?

Anyone else had this before? Im assuming the trans will need to be pulled out by a shop for further investigation (I dont have the tools at home to do it myself).

 

Rear main seal leak impacting all M177 motors? - MBWorld.org Forums maybe this problem ?

 

I just re-read your post. Is there definitely oil coming down from above the black plastic pan area?

 

The oil is coming down from the half circle between the engine and trans, then spreading along the top of the oil pan

 

This

Might hopefully be a better picture

 

This

Might hopefully be a better picture

 

Although some people claim it's an issue for the M177 in general, the main seal leak hasn't really been observed outside of the E63 and the G63, but it's starting to affect the E and G widely it seems. Not all M177 variants are the same.

 

Two possibilities for your leak
1. Front pump seal on the transmission
2. Rear main seal plate leak.
There was a TSB for the MCT transmission leaking out of the front cover seal. Unfortunately the transmission will have to be removed for either rear main seal plate or front cover inspection.

 

Looking at your pictures more closely the color resembles engine oil more than trans oil. I believe the trans fluid color on the older MCT 7 speed transmissions was Blue or Red depending on origin spec. The new 9 speed MCT uses gold fluid so it’s harder to differentiate from engine oil. If your PCV breathers are plugged it will cause excessive crankcase pressure and blow out the engine seals. Something to consider before repairing. There’s always a cause and effect.

 

OP, did you end up solving the issue, was it transmission fluid or engine oil?

 

Its 100% engine oil, So im onto my second shop to look at it for me after the first one stuffed me around.

The second shop removed the inspection port in the bell housing and couldn't see any oil. They then removed the engine speed sensor and found that covered in oil, then poked a bore scope in and then confirmed leak from rear of upper sump inside the bell housing.

Just waiting for my mechanics to have a big enough window to book out three days straight as the trans needs to come out to confirm exactly where its coming from but I still think its the rear main seal unfortunately

 

RMS on the C 63 S version of the M177 is rare, I am sorry to hear about that : (

 

Has anyone implemented a catch can solution without tripping the check engine light?

 

What is your driving style? Do you boost hard at low rpm (this is a very effective way to generate a lot of crankcase pressure)?

 

Finally got this sorted, mechanics dropped the trans. He inspected the rear main and commented that he could spin it by pressing it with his thumb. Much to his shock it fell out with little pressure from a flathead screwdriver.

New seal went in fine (and is nice and tight now) serviced the trans at the same time. Now leak free and $4,126 (NZD) bill for parts and 20 hours labor.

 

Glad it is sorted out, I wonder if the oil pump solenoid mod would help prolong the life of the RMS?

 

Cant say I've heard of the oil pump solenoid mod before?

 

No. Crankcase oil pressure surrounding the crankshaft is “ambient”, much lower than pump pressure.

RMS failure in M17x is from too much crankcase air pressure or too little (vacuum).

The oil pump solenoid mod gives more flow and has either no effect, or a harmful effect on the RMS by virtue of higher pressure with higher flow.

 

That is a shame : /