Trying to figure out if this is a failed RMS or something else.

I bought my E63S last fall (~65k miles) and about a month later noticed a decent oil leak. I cleaned everything up to try to track it down, but winter hit and I didn’t get back under the car until now, after a few months and ~3k miles.



I’m aware of the common RMS/AOS issues on these cars. Nothing showed up during the PPI, though I know that doesn’t mean much. Carfax shows a cylinder head replacement years ago and at some point the transmission was removed for unknown work. I may try contacting that dealer for more details.

What makes me question the RMS is the amount of oil forward of the transmission on the oil pan. There’s oil at the engine-trans mating surface, but it doesn’t quite look like the RMS leaks I’m used to seeing (I’ve worked on plenty of German cars over the years).

For reference, I only get about one small drip on the garage floor every 3-4 weeks, but the belly trays have definitely collected oil, so it’s clearly active.

Curious if others with failed RMS leaks have seen oil travel forward onto the oil pan like this, or if I should be looking elsewhere.







Here’s a video showing the area from some better angles as well.

 

Forgot to add, is there an inspection port on these trans I can use a scope to inspect? That’d be a solid way to rule the RMS out..

 

That almost seems like a lower oil pan leak. I would clean everything up again and leave the panels off and see where it reappears. You have to clean everything up though and then start at the valve cover gaskets and work your way down until you spot fresh oil. Does not look like an RMS real as that is typically very apparent at the mating surface between the block and the trans. It typically drips down onto the sway bar and then down to the tray.

 

My head went to the oil pan as well. I’m due for an oil change so might clean it up and throw a new oil pan on while I’m at it, and keep an eye on it. A new oil pan is less than an hour of diagnostic fee, so it’s not a terrible wager.

 

@LongRoof88 I wouldn't change the oil pan until you confirm the cause of the leak. Something I've learned over the years. Find the cause, then correct. Don't throw parts at it since you could be creating new problems (a new leak location).

As mentioned by @superpop, I'd degrease and wash the entire underside and leave the under trays off. If you have a leak (and do a good scrubbing), you should see the seep in relatively few miles (or you'll notice more places you need to scrub up with a brush and some Dawn detergent. I've heard of some UV dies people use to better detect leaks but never tried them myself.

Let us know what you find.

 

Definitely a fair point- I typically am not a throw parts at it approach person. I have cleaned up the oil- I’m out the country for the next week and a half for work while parts come in. I plan to look to see if there’s any seepage while I’m away and it’s sitting. If nothing new shows up I’ll drive it for a bit before changing anything and see if I can track it down.

thanks for your insights!

 

Agreed, oil pan.

Trenton O. Gibson
tgibson@highline-autos.com
Highline Autos
Direct: 602.909.9216
Office: 480.348.0777

 

When my OVS "were" working, I developed an upper oil pan gasket leak. When the OVS start clogging or not working, other gaskets take the brunt of it. Not only my upper oil pan gasket, my RMS, and a valve cover......

 

Is it true that making sure the car gets fully exercised (high rpm, fast acceleration) helps keep the oil separators open?

 

I am not a mechanical engineer but I do like to take things apart, especially when they fail, to understand what the root cause was. I had the OVS units replaced on my car a few months ago after dealing with the RMS leak and a few other things. I had my Indy do the work and Fidelity covered the repair for the most part. I asked my indy to keep the old units for me so I could take a look at them. Of note, the new units had different part numbers than the ones they replaced. It has been rumoured that MB changed the design around 2021 but I have no way of proving that. I did dissect the old OVS units and posted this on youtube if you are interested. My summation is that there is a spring loaded door or valve device in the OVS that gets sticky over time and does not move as freely. It would appear that it gets stuck in the closed position and this can cause excessive vacuum in the crankcase. I was expecting to find a device filled with carbon and sludge but it was actually fairly clean, just oily. The only smoking gun I could find was that this spring loaded valve gets stuck with a buildup of sticky residue that prevents the valve from moving freely. I sprayed it with some brake cleaner and it freed right up. So, my assumption is that this is a flaw in the design of the OVS units that has since been rectified. I do not believe that any style of driving or temperature fluctuation would have a material effect on this device. It was not clogged in my case, but rather, mechanically stuck. An easy way to tell if these devices are clogged is to start the car up and then try to remove the oil cap. If it is very hard to turn and lift off, you have a problem. There should be a little vacuum but not so much that you cannot remove the cap with your fingers. Regardless, if you have a 2018-2020 AMG car with the M177 LS2 motor, I would highly suggest having your OVS units replaced with the newer version. It is a few thousand bucks to do but the collateral damage avoidance that it affords is substantial.

 

Well, cleaned everything off and took it into town. Ended up having a rather spirted drive back. About 12 miles round trip.

Put it right back up into the air and was surprised to see this much oil. I definitely have oil seeping out through the back of the lower (plastic) oil pan. I tried adjusting the light so you can see the wet film along the back edge of the pan. What I don’t love is seeing that much oil at the trans-engine mating faces. I’m having a hard time believing the seepage at the pan is traveling back and accumulating at the trans that quickly.

It seems I might have excessive crankcase pressure to the point it’s blowing out the oil pan gasket and the RMS?? Oof.

I do have some moderately slow 1st and reverse engagement (beyond what I think would be normal for an MCT, but I’m speculating). Hoping the trans hasn’t also fallen victim here too.

Might be time to button it up and send it to an Indy. Few years ago I would be looking to tackle this myself, but with a second kid arriving in a few months, I can’t give this the attention it needs.

Worth trying to replace the oil pan that’s on the way and seeing I’m still getting accumulation at the trans? But if it’s due to excessive crankcase pressure due to failed oil separators, the pan is just going to fail again.

 

That is most definitely RMS failure. Pan swap is simple but I would just hand it to your indy and have them swap it when they drop the trans as they have to drain the oil at that point anyway. If it was me, I would bite the bullet and have your indy drop the motor and trans as one and do the following. RMS, OVS, Motor Mounts, Belts, and Plugs. Far cheaper to do this all at once rather than doing it piecemeal. Assuming you have not already done this stuff and that mileage is around 68K at this point. Once you do all of that you should be set for a very long time assuming you want to keep the car for a while. Otherwise you could just fix the RMS and move it along.

 

Let it sit overnight and checked it out this morning. Oddly enough there is accumulation on this hose (as was evident also before cleaning), which seems to be originating from above. You can see the light reflecting off the oil right above/between the two hoses on the trans housing, rear of the transmission/engine interface. Was headed off to work so did not investigate further. But has me wondering where this is coming from. Either way looks like at a minimum the trans is coming down.

 

I 100% agree with this.

 

I just want to understand better. Are you saying that once your OVS failed, your car leaked in all three places? How much did it cost to get all that fixed???

 

Correct. I believe when my OVS started failing the oil pan gasket was the first leak along with the seeping the RMS. The upper oil pan gasket and RMS were covered through the dealership I bought the car from, so it didn't cost me anything. The valve cover gasket was further down the road but was big job. The whole time my OVS tested "good". It wasn't until I had the VCG fixed that I replaced the both OVS (warranty covered about half, and I was out of pocket $4,700). I have since added the 63 motorsports catch cans as well.

This is directly from my post on the RMS fail club thread

https://mbworld.org/forums/w213-amg/...m_content=post

I believe from personal experience that the OVS not only knock the RMS out but the other gaskets and seals as well the worst they perform. It only makes since if the OVS are compromised/clogged/failed ect....crankcase pressure will find the next weakest link.

 

Thanks for all the details. And I feel really bad that you had to deal with all that drama and costs! Did you by file your complaint with the NHTSA?

 

I did file a complaint. However, I will love the m177 (or I really hate money) and at the end of the year I am planning on purchasing a 20/21 S63 sedan... so yeah.

 

Thanks for filing your complaint. If everybody who experiences the probelm files a complaint we can get attorneys involved for a class action lawsuit, but they won't begin to investigate without seeing the NHTSA complaints first. I have a 2018 S63 sedan and haven't had the RMS/OVS/VCG problem, at least not yet.

FYI, the S63 sedans with the M177 were 2018-2020, but they did build the coupes for the 21 model year. Definitely go with a 2019 or 2020 sedan, they have the upgraded MBUX system over the old system that's in mine.