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As I am finally in possession of new brake calipers/hoses/pads and LCA kit, I started work today on my '14 E550 coupe. In dropping the covers underneath, I found two surprises of the not great kind. There isn't a ton of oil leakage yet, however I aim to resolve while the car is up on stands if possible. Would anyone care to offer any suggestions on source of issue(s) based on these photos attached? Not in a hurry, and ready to take more pics or explore based on suggestions...
I'd clean all the oil off, then run it and look. I often use paper towels for difficult to find leaks where the oil gets all over. I clean, then pack the suspect areas with paper towels, then peel them off to reveal the spot.
Often times, when it's too much work to replace a gasket (which is almost always imo), I'll put a vacuum on the eng and clean the leaky spot with carb or brake cleaner. That way it cleans inside the leak path so the silicone can stick inside, otherwise the silicone will just be a surface patch that will usually not hold for long. I also remove any excess loose gasket at/around the leak point. Once I'm satisfied it's clean I apply silicone sealant, with vacuum still on it the whole time to prevent oil from getting back in the leak path. I mush the silicone in real good so hopefully it gets into the hole and seals it. It usually works but not guaranteed. For example it may be a weeping fiber gasket, which you can't do a whole a lot for because you can't clean it enough for the silicone to stick. This is why I coat fiber gaskets with silicone before I install them, and I really rub the silicone into them to be sure oil never gets into them in the first place. Then there's rubber gaskets that harden, which silicone can seal by cleaning and mushing silicone in, but not always. Basically any spot you didn't get squeaky clean and pack with silicone will likely leak again, but probably leak much less than before. Imo it depends a lot on crankcase pressure. If there is truly never any pressure then a lame patch job will hold for a long time, but if there is any pressure it'll be very short lived. With a turbo eng you gotta wonder if you have crankcase pressure. I just checked mine last week and it shows no vacuum or pressure under any conditions. I had to check the gauge afterwards to be sure it was working because that was hard to believe, but it's correct.
I prefer to use a strong vacuum for this repair job, which is the engine itself or ideally vacuum from a second car which I run a hose to. The vacuum to the brake booster hose is a great source to tap an eng. A shop vac will work too, it's just very weak compared to an eng. Oh, and you have to seal the eng you're actually sucking a vacuum on it, so plug the PCV passage(s) and be sure it's actually sucking a vacuum on the eng.
As for suspects, I'd suspect the valve covers, but there are sooo many places it can leak, like the cam positioners, so I'd just clean it before anything. I usually don't bother with small leaks because they usually don't hurt anything, but that is entirely up to you
12-28-2022, 05:02 PM
