When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hey everyone, I did a PCV overhaul and replaced the rear oil separator / cover + the low-load driver side breather. The issue is that the new driver side breather gasket seems to be seeping a small amount of oil after a few days of driving. I've tried re-installing it 3 times and make sure both mating surfaces are perfectly clean prior to install and it still seeps. The old one did not leak at all, I just replaced is as it was the original unit and now I can't get this thing to stop leaking....any ideas?
First I want to say there is zero reason to replace the drivers side oil separator unless it is leaking oil. To those that never saw the inside of it, there are no moving parts, nothing to fail. I simply removed and cleaned it, then reinstalled. In my case the gasket was fine. This gasket is not as soft as the passenger side cover that flattens out.
heres what it looks like when you separate the cover.
What brand is the new cover, Mercedes or aftermarket? I actually bought an aftermarket cover and when i received it the gasket looked a little small, wouldn't sit perfectly in the groove. I remember thinking there's no way im installing the aftermarket one after seeing it. The two pieces wouldn't even snap together properly. If you still have the old one maybe clean it up and reinstall it. Like I said I was able to clean mine and reinstall it, no leaks. Be careful cleaning the gasket, just soap and water.
Did you properly torque the bolts? They are only 12nm.
First I want to say there is zero reason to replace the drivers side oil separator unless it is leaking oil. To those that never saw the inside of it, there are no moving parts, nothing to fail. I simply removed and cleaned it, then reinstalled. In my case the gasket was fine. This gasket is not as soft as the passenger side cover that flattens out.
heres what it looks like when you separate the cover.
What brand is the new cover, Mercedes or aftermarket? I actually bought an aftermarket cover and when i received it the gasket looked a little small, wouldn't sit perfectly in the groove. I remember thinking there's no way im installing the aftermarket one after seeing it. The two pieces wouldn't even snap together properly. If you still have the old one maybe clean it up and reinstall it. Like I said I was able to clean mine and reinstall it, no leaks. Be careful cleaning the gasket, just soap and water.
Did you properly torque the bolts? They are only 12nm.
It’s a third party OEM PCV made by Febi. It feels the exact same as the factory one and the gasket also looked identical. The only thing I can think of is that the first install wasn’t perfectly clean and some residual oil is keeping it from sealing properly once it heat cycles. I have a new one coming for free and will try it again. I also only torqued it down to 9 NM based on FCP euros recommendations so I’ll try 12 NM now, thank you!
Update on this, new unit sealed well for 2-3 days but is leaking again. I’m beginning to think I need to buy the Mercedes part in hopes the rubber seal does a better job. The only other thing I can think of is using some sort of abrasive to clean the mating surface more aggressive than I already have using scotch brite pads.
I would only use dish soap and warm water or some degreaser to clean the area. I would not use an abrasive, you want it as smooth as possible.
When I tightened the cover down I set it at 6nm at first then to the 12nm. I did this because I have a cheap harbor Freight torque wrench so wanted to make sure I didn't over tighten and flatten the gasket.
Have you checked/inspected the hose connected to the cover going to the throttle body, is it clear?
Have you checked the oil level, make sure its not over filled?
I would carefully unbolt and remove the cover and try to see exactly where the oil is seeping out from. Clean everything up and install it again.
I used a Febi brand oil separator cover from FCP on the passenger side, I ended up having to go back and tighten the bolts down at least 3 times now due to it leaking oil. If you have done the passenger side you know its not possible to get a torque wrench on it. oddly enough the old cover was Mercedes brand and was not leaking at all.
It seeping from the bottom portion only and making its way to the screw and from there collecting on the valve cover. All times its leaked it was from the same bottom area. I'm starting to think 12NM might be too tight with blue loctite and maybe 8-9NM with blue loctite is the right amount. The first 2-3 times I tightened it down I think some oil made its way into the bolt area and with the engine vibration it slowly loosened the bolt causing it to leak from the bottom again.
The bolts are outside of the gasket, so oil shouldn't be getting to the bolts.
The area should be totally clean of all oil before installing the cover back on.
Its either the new cover/gasket is faulty. The engine surface is not properly cleaned or flat. Faulty bolts. Hose is clogged.
I did not notice any type of thread locker on the original bolts on mine. When I look up the replacement bolts there does not appear to be any type of thread locker on them. From my experience new bolts come with thread locker already applied, dry, if a thread locker is requiered.
I did not use any type of thread locker on my cover. I set my torque wrench to 12nm final torque. No leaks.
The oil is seeping past the rubber gasket and making its way into the bolt area.
Either way, I've had 2 different FEBI units and they both leaked - I cleaned the surface area many times and used an IPA alchohol based prep spray to clear the surfaces and it still leaks. There is a very faint outline of where the old gasket was that I cant seem to remove, I'm going to try and rub with brake cleaner tonight and then wipe off with the IPA cleaner and then reseal it again.
I should note, I never had a leak prior to replacing it - should have never touched it....
The oil is seeping past the rubber gasket and making its way into the bolt area.
Either way, I've had 2 different FEBI units and they both leaked - I cleaned the surface area many times and used an IPA alchohol based prep spray to clear the surfaces and it still leaks. There is a very faint outline of where the old gasket was that I cant seem to remove, I'm going to try and rub with brake cleaner tonight and then wipe off with the IPA cleaner and then reseal it again.
I should note, I never had a leak prior to replacing it - should have never touched it....
Well I did the same, both of my covers were not leaking any oil but I had the bright idea of replacing them anyways as part of preventative maintenance. To my surprise everything looked great, the passenger side even looked like it had been replaced and was in very good condition. Even the drip pan looked fine.
Try to gently remove the gasket and clean it with dish soap and water then put it back in the groove. make sure theres no oil on it. When you put the bolts back go around the cover tightening each one a little at a time so the cover seats as evenly as possible.
Maybe try another brand than Febi. The defect from one could have carried to another, especially if the case and/or gasket is produced from the same defective mold.
Maybe try another brand than Febi. The defect from one could have carried to another, especially if the case and/or gasket is produced from the same defective mold.
I might just grab the part from the dealer - it makes no sense that this part is so sensitive to installation that it leaks if torque specs are off slightly. I’m beginning to think it’s a defective mold/part as you say.
Here is a photo of the mating surface last night before I installed again.
Like I said the aftermarket cover i had received, I think the brand was Dorman, the 2 sections of the cover would not snap together firmly, it would move when I pressed my thumb against it. The Mercedes cover snapped together nicely. Try pressing the inner piece of the cover and see if it moves in the cover.
Also the gasket looked slightly small, when I installed it in the groove it stretched a little and looked off at the corners.
Thats why I put the old mercedes cover back on. The quality of the aftermarket cover didn't look good.
Im surprised with Febi though, usually the brand is good.
Yea, I actually opened this one up VERY easily and they didnt snap together firmly at all....very flimsy feeling. I'm thinking this Febi unit is just poor quality which I opted for vs the URO brand. Sadly, I threw out the original part when I made the initial swap.
Yea....I ended up ordering another part from URO - hoping this one works. If it doesn't I'll have to bite the bullet and special order it from the dealer for around $75.
Im cheap and have had good luck buying used Mercedes parts off ebay so far. Can always look for used, I found one for $15 OBO, the gasket looks very good.
Im cheap and have had good luck buying used Mercedes parts off ebay so far. Can always look for used, I found one for $15 OBO, the gasket looks very good.
I just installed a new URO one, let’s see how this holds up. It seems to snap together a lot better than the FEBI and I think its shape is marginally different too.
Hopefully that Uro part works. i came across another used cover cheap and the gasket looks good. I wouldnt buy a used cover for the passenger side since that gasket is soft and flattens out easily, but the gasket on these drivers side covers seems thicker.
Hopefully that Uro part works. i came across another used cover cheap and the gasket looks good. I wouldnt buy a used cover for the passenger side since that gasket is soft and flattens out easily, but the gasket on these drivers side covers seems thicker.
I’m still monitoring but after driving around for 2 days and I don’t see a spec of oil. Looks like the URO part made a much better seal - it also snapped together much better than the FEBI unit.
I would not sand down anything. Theres no reason the surface should not be flat, unless something was done to it?
Find a small straight edge and go all around it where the gasket seats and see if the surface is deformed. Can probably use a credit card.
Unless there is something wrong with the bolt holes, stripped maybe?
That used cover I posted above for $7.50 looks fine to me, I would have no problem buying it and trying it out. Clean it really good with dish soap and water.
The photo you posted in #20 above the cover does look really oily. have you checked your oil fill level, make sure its not too full? Im a bit shocked that two covers no are leaking.
I would not sand down anything. Theres no reason the surface should not be flat, unless something was done to it?
Find a small straight edge and go all around it where the gasket seats and see if the surface is deformed. Can probably use a credit card.
Unless there is something wrong with the bolt holes, stripped maybe?
That used cover I posted above for $7.50 looks fine to me, I would have no problem buying it and trying it out. Clean it really good with dish soap and water.
The photo you posted in #20 above the cover does look really oily. have you checked your oil fill level, make sure its not too full? Im a bit shocked that two covers no are leaking.
I just did it again, this time I made sure to use a lot of loctite on the bottom bolt. When I was removing the screws that one came out easier and definitely had some oil between the threads. I have a feeling the oil is seeping into the hole somehow and then the vibrations are loosening the bolt.
If this doesn’t work I’m going to grab a OEM used unit from a local junkyard.
03-28-2024, 12:07 PM
