MB W211 M112 with Rear Main Seal leak

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charlesb2003

charlesb2003

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Jacksonville, FL
Just bought a 2005 Mercedes-Benz E320 (M112 V6 engine) and the dealership says it's got a rear main seal leak. Car has 198,000 miles on it and I know it was fed a steady diet of Mobil 1 0w40 European Formula oil from new until at least 118,000 miles. After that I have no idea what it has seen, and there is a bit of sludge in the oil cap. I will know more about the sludge situation soon when I change the leaking valve cover gaskets and refurb the PCV system, but I'm debating whether or not to run Auto-Rx as a cleaner and seal conditioner.

On their website, for Auto-Rx Plus, it says it's possible to use dino or synthetic oils for a cleaning cycle, though it suggests a Group III oil such as Pennzoil Platinum. However for seal conditioning and leak reduction/elimination, it says to only use conventional oil, and that returning to synthetic after could cause the leak to return. I am not aware of any conventional oils that meet the MB 229.5 spec required for my car. I am not worried about warranty compliance, but I have always used full synthetic oils in all my vehicles. Any suggestions?
 
I've run Castrol GTX High Mileage 20-50 in my old Alfa spider for years. Tried Mobil 1 15-50, top end was much louder, started to get a few drips from my rear main, and it would blow a little smoke after idling a while. Went back to the GTX and all the problems went away. I never really believed synthetic would cause leaks before, but I do now.
 
Originally Posted by stoan
I've run Castrol GTX High Mileage 20-50 in my old Alfa spider for years. Tried Mobil 1 15-50, top end was much louder, started to get a few drips from my rear main, and it would blow a little smoke after idling a while. Went back to the GTX and all the problems went away. I never really believed synthetic would cause leaks before, but I do now.


Was your Alfa spec'd to run synthetic from new? In my case, synthetic is required by the manufacturer. How could running synthetic in an engine designed to run synthetic cause seal leaks? From what I've read, these engines have a uniquely designed rear main seal that is prone to leaks, but I just don't want to do anything to make it worse. Also don't want to fix the leak at the expense of wearing out the engine, which would be my concern running conventional oil. Would rather just pop for a new rear main seal in that case, but hoping to avoid that if possible.
 
Try Bars leak rear seal fix or replace the rear seal. Not knowing how long you intend to keep this car at 200K its not uncommon to have a some seal leakage, at least the Bars leak stuff wont do any more damage. Do not use ATP, its an extremely strong solvent that softens the seal but in time the seal can disintegrate and can make things worse.
Fixing it is the right way and anything else is a hail Mary pass.

keep in mind these every one of products will effect every seal and gasket they come in contact with so going this route may have some serious consequences down the road in the form of new leaks. Some are easier on the materials than others, the Bars leak seems the be less aggressive than others from my experience.

https://barsleaks.com/product/concentrated-rear-main-seal-repair/
 
With that kind of mileage I'd run a high mileage oil of the appropriate weight and just change it every 5k miles or fix the RMS. Remember that long drain intervals are a prime component for OE oil specs.
 
Last edited:
You're in a bit of a tough spot. Looking for a conventional oil that won't wear out a 200k engine? You could try a HDEO such as Delo 15W-40, but as you've stated you don't have good options here.
 
Originally Posted by stoan
I've run Castrol GTX High Mileage 20-50 in my old Alfa spider for years. Tried Mobil 1 15-50, top end was much louder, started to get a few drips from my rear main, and it would blow a little smoke after idling a while. Went back to the GTX and all the problems went away. I never really believed synthetic would cause leaks before, but I do now.



Synthetic doesn't cause leaks. Synthetic prevents deposit formation around seals, so when the seals reach the end of their service life they start to leak.
 
Originally Posted by Danno
You're in a bit of a tough spot. Looking for a conventional oil that won't wear out a 200k engine? You could try a HDEO such as Delo 15W-40, but as you've stated you don't have good options here.



this is exactly what I did with my ML320, the oil consumption is now about 1/2 litre between changes (every 6 months or 5000 miles)

and the engine is spotless inside
 
It's very common in the M112/3 engines, my CLK430 started weaping around 80k last year, but I'm not noticing any increased consumption or use in 7500mi OCIs, so I'm watching it until it gets worse (it's a bit intermittent now). I have noticed it went from one drip per night on M1 0w40 to about one drip every 3-4 days on Castrol 5w40 with the older 229.3 speced oil my car is still ok to use (229.1 was the owner's manual spec).

I think MB updated the seal to prevent this if you do end up replacing it, I'm deciding if I want to just bite the bullet and do it as the car isn't going anywhere and is a weekend cruiser in otherwise excellent shape with about 90k miles
 
Maybe I shouldn't have said synthetic causes the leaks. Age causes the leaks, but it's easier for the synthetic to leak. I know with my 34 year old engine, Mobil1 leaks and smokes, GTX High Mileage doesn't . And the cam slapping against the flat tappets is much quieter with the GTX High Mileage.
 
Originally Posted by charlesb2003
Originally Posted by stoan
I've run Castrol GTX High Mileage 20-50 in my old Alfa spider for years. Tried Mobil 1 15-50, top end was much louder, started to get a few drips from my rear main, and it would blow a little smoke after idling a while. Went back to the GTX and all the problems went away. I never really believed synthetic would cause leaks before, but I do now.


Was your Alfa spec'd to run synthetic from new? In my case, synthetic is required by the manufacturer. How could running synthetic in an engine designed to run synthetic cause seal leaks? From what I've read, these engines have a uniquely designed rear main seal that is prone to leaks, but I just don't want to do anything to make it worse. Also don't want to fix the leak at the expense of wearing out the engine, which would be my concern running conventional oil. Would rather just pop for a new rear main seal in that case, but hoping to avoid that if possible.



The decal under my hood says to use Agip, IP, or Shell, all in 10w-50. I don't know where to get any of those so I just use what I think is best.
 
Thanks for all the replies. I plan to keep the car a good while, it's in surprisingly good shape considering the mileage. I got it for a song because the SBC braking system was shot and it needed an air strut, but I got the SBC pump replaced for free at the dealership under the 25 year warranty extension and got a rebuilt Arnott strut for $500 so I am definitely ahead financially on this one.

I did not notice the RMS leak when I looked at the car pre-purchase. I did see both valve cover gaskets leaking so I thought that was the reason for the oil all over the engine. It's not a very fast leak at all, I have driven it about 1000 miles and the level hasn't dropped far enough for the sensor to measure it. (Side note, anyone know where to get a dipstick for this thing!?)

I will be changing the spark plugs and wires soon and when I do I will also change out the valve cover gaskets and reseal the PCV system and change all associated hoses. This should stop all the leaks on the topside of the engine, and give me a better idea of the level of sludge in the engine. I don't have the proper tools and equipment to tackle changing the RMS myself though, which is why I'm trying to avoid it if possible. However if it comes down to it I will have to find a good independent shop and get it done.


Back to my original question, which oil would you recommend to use with Auto-Rx that would be safe with this engine? I've read about it on this forum enough to believe that it may be the best option I have to deal with both the accumulated sludge and grime from 200k miles and potentially fixing or slowing the RMS leak. I don't mind a shorter drain interval, but I don't want to lose any of the wear protection that's offered by a proper synthetic oil meeting MB 229.5 spec.

I'm not opposed to running an oil that doesn't meet the spec, I ran Rotella T6 5w-40 in my old E39 and although it didn't meet the BMW LL01 spec it was a good quality synthetic oil. I guess my main fear is putting conventional oil in an engine designed to run synthetic. Am I right to fear this, or am I overreacting?
 
synthetic oil was required in the engine to accommodate the MB FSS which allowed up to 18, 000 KM oil change intervals (way to long in my opinion), this happened to my recollection around 2000-2001

they also had a recall and a tsb over sludge damaged engines when the OCI was 10, 000 to 20,000 miles with dino engine oil

http://www.peachparts.com/shopforum...l320-99-engine-failure-77-000-miles.html

before this a HDEO was totally acceptable with an OCI of 6 months or about 5,000 miles

lots of MB engines lasted well into 300, 000 miles on 15w40
 
I don't know anything about the Bars Leak seal product but since Trav recommendated it, I would try it. The thing I don't like about Auto-RX is how much of the volume is comprised of lanolin goo particles. They get stuck in some low-flow places in engines and a whole bunch end up in oil filters. In my VW 1.8T I had, some got stuck on a vertical surface visible through the oil fill hole. I'm just not comfortable with them. I have filtered them out of new Auto-RX using coffee filters and days worth of draining. They clogged the filters, requiring multiple new filters.

Your engine is not a super high oil temperature engine, so I do not think it is critical that it only get synthetic.
 
It sounds more like a weep than a leak, change the valve covers and throw a bottle of Rislone concentrate in there, it has a small amount of esters may help the seals and will do a little cleaning at the same time, I probably wouldn't get too aggressive with this one, it doesn't take much to turn a weep into a full blown leak.
You do not have to alter the oil you normally use but you may want to shorten the oci a little and cut the filter open for a look see.

If you park the car up hill with cardboard under it and don't get oil spots on the the cardboard its honestly nothing to worry about.
 
Originally Posted by JAG
I don't know anything about the Bars Leak seal product but since Trav recommendated it, I would try it. The thing I don't like about Auto-RX is how much of the volume is comprised of lanolin goo particles. They get stuck in some low-flow places in engines and a whole bunch end up in oil filters. In my VW 1.8T I had, some got stuck on a vertical surface visible through the oil fill hole. I'm just not comfortable with them. I have filtered them out of new Auto-RX using coffee filters and days worth of draining. They clogged the filters, requiring multiple new filters.

Your engine is not a super high oil temperature engine, so I do not think it is critical that it only get synthetic.


You just scared me off the Auto-Rx in one post! Last thing I want is anything getting clogged up. The only reason I was considering running non-synthetic was to run Auto-Rx as directed, but now I don't think I'm going to. What are your thoughts on Kreen? I ran that in a Volvo S60 I had with a moderate sludge problem and it cleaned it right up and did not cause any leaks, but it also wasn't seeping already.

Originally Posted by Trav
It sounds more like a weep than a leak, change the valve covers and throw a bottle of Rislone concentrate in there, it has a small amount of esters may help the seals and will do a little cleaning at the same time, I probably wouldn't get too aggressive with this one, it doesn't take much to turn a weep into a full blown leak.
You do not have to alter the oil you normally use but you may want to shorten the oci a little and cut the filter open for a look see.

If you park the car up hill with cardboard under it and don't get oil spots on the the cardboard its honestly nothing to worry about.


I haven't tried cardboard, but the concrete where I park is spotless after days of sitting. Filter is a cartridge type so it will be easy to see, I will post pics of the filter that's in there when I change the oil for the first time which will be right after changing the valve cover gaskets and PCV hoses. Would you recommend Rislone over Bar's leaks since it's just a slow weep?


Thanks again for all the helpful replies!
 
Also, any thoughts on Lubro-Moly Motor Oil Saver? I've used their MoS2 product in every engine I've owned for the past 10 or so years with varying degrees of noticeable improvement but never any negative side effects. In fact, I have already added about a third of a can to this car and I plan to add the rest when I change the oil.

https://bobistheoilguy.com/forums/ubbthreads.php/topics/2018411/Re:_Lubro-Moly_Motor_Oil_Saver

According to this post, the Motor Oil Saver can be added with MoS2 and claims to clean engine internals and condition seals as well.
 
Originally Posted by charlesb2003
This thread in particular concerns me:

What concerns me most about that link is that it concerns itself primarily with viscosity and secondarily with brand, over the appropriate specification, which I am assuming would be MB 229.5, which lists all formally approved oils. Others here will correct me if I've grabbed the wrong sheet.
 
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