Hi guys, yes I have that strange M119 oil draining back into the sump over many days issue. Now just to put you into the picture, this happened prior to my engine rebuild by Vath Engineering in Frankfurt, and the same issue continued after the rebuild. Since the bebuild, I read many reports about changing the oil check valve in the filter housing. So I did this, and still the problem persisted. I lost heart in the car and it has sat for seven years dry stored.
Now things are less hectic in my life, and I decided to get back at it. I dropped the sump to check the pump and filter pickup, all okay. I then went back to the filter housing and once again removed it. It’s a little difficult to remove, but I found that removing the protective plastic splash guard, which protects the alternator makes removing the filter housing much easier to remove from underneath. What I then did was block off the two upper oil outlets with aluminium tape, and also the oil cooler inlet and outlet ports. I then filled the filter bowl with oil, but realised almost immediately that oil was leaking from another port. This one is a normal drain away for when the oil filter cap and bolt are removed to gain access to the filter, without the filter bowl being full of oil. This action of actually removing the bolt allows the filter bowl to empty. So I cleaned up the spill and refilled to observe the check valve was not leaking.
For those of you not sure the reason for the check valve, well it’s purpose is to stop oil back filling into the sump on engine shutdown. Okay, this was fine. I then removed the tape from the port that originally leaked, which was my mistake after not fitting the bolt...I should add that at this stage, I left the cap off and just fitted the bolt to observe no leaks.
I left the filter bowl in an upright position over night, and guess what, oil was leaking out between the bolt and retaining nut in the bottom of the unit. This was the source of my slow leak. I removed the remaining oil and bolt, and cleaned everything up and tried a small amount of Teflon tape around the thread of the bolt and refitted everything and refilled with oil. Twenty four hours later, no leaks.
To cut a long story short, no new filter bowls available from MB, although the bolt is available, and I have one on order, and no, you cannot only change the nut, it’s built into the bottom of the unit. I am thinking that what’s happened over the years is that various mechanics have over tightened the filter bowl cap bolt, and stretched both the threads on the bolt and retaining nut. Not much I can do about the nut, but at least I can change the bolt, And yes, I will still add a small amount of Teflon.
I did do a quick eBay search and did find one filter bowl with the oil cooler outlets in California for sale as a secondhand unit, but it could be as bad, or worse that my unit. Just also be aware that there is a second oil check valve mounted inside the block underneath the oil filter housing, it’s a screw in unit and can only be accessed by removing the filter housing, it also got changed.
Sorry guys I know this is long winded, but I thought it may help some of you guys who have also replaced the main oil check valve, but still have the same problem as me. I really hopes this is helpful.
Now things are less hectic in my life, and I decided to get back at it. I dropped the sump to check the pump and filter pickup, all okay. I then went back to the filter housing and once again removed it. It’s a little difficult to remove, but I found that removing the protective plastic splash guard, which protects the alternator makes removing the filter housing much easier to remove from underneath. What I then did was block off the two upper oil outlets with aluminium tape, and also the oil cooler inlet and outlet ports. I then filled the filter bowl with oil, but realised almost immediately that oil was leaking from another port. This one is a normal drain away for when the oil filter cap and bolt are removed to gain access to the filter, without the filter bowl being full of oil. This action of actually removing the bolt allows the filter bowl to empty. So I cleaned up the spill and refilled to observe the check valve was not leaking.
For those of you not sure the reason for the check valve, well it’s purpose is to stop oil back filling into the sump on engine shutdown. Okay, this was fine. I then removed the tape from the port that originally leaked, which was my mistake after not fitting the bolt...I should add that at this stage, I left the cap off and just fitted the bolt to observe no leaks.
I left the filter bowl in an upright position over night, and guess what, oil was leaking out between the bolt and retaining nut in the bottom of the unit. This was the source of my slow leak. I removed the remaining oil and bolt, and cleaned everything up and tried a small amount of Teflon tape around the thread of the bolt and refitted everything and refilled with oil. Twenty four hours later, no leaks.
To cut a long story short, no new filter bowls available from MB, although the bolt is available, and I have one on order, and no, you cannot only change the nut, it’s built into the bottom of the unit. I am thinking that what’s happened over the years is that various mechanics have over tightened the filter bowl cap bolt, and stretched both the threads on the bolt and retaining nut. Not much I can do about the nut, but at least I can change the bolt, And yes, I will still add a small amount of Teflon.
I did do a quick eBay search and did find one filter bowl with the oil cooler outlets in California for sale as a secondhand unit, but it could be as bad, or worse that my unit. Just also be aware that there is a second oil check valve mounted inside the block underneath the oil filter housing, it’s a screw in unit and can only be accessed by removing the filter housing, it also got changed.
Sorry guys I know this is long winded, but I thought it may help some of you guys who have also replaced the main oil check valve, but still have the same problem as me. I really hopes this is helpful.
