M103 Oil Loss - A cheap bastard's approach - PeachParts Mercedes-Benz Forum

tinypanzer · #1 10-11-2010, 05:43 PM

As anyone with an M103 can attest, keeping the oil on the inside of the engine can be a bit of a challenge. Apart from the horrible valve cover gasket that needs annual replacement, and the timing cover seal that lasts 3 years if you're lucky, there's also a couple other places you can lose oil (valve stem seals) and of course, the most ironic place of all to lose oil from, the low oil sensor.

I had noticed some oil around my low oil sensor, and assuming that the o-ring was shot, I replaced it. Well, that didn't stop the leak. It turned out that oil was seeping through the sensor where the plastic is inserted into the metal.

Now, I know I am going to catch all sorts of flames for doing this.... I took a tube of the MB sealant I had opened a few days earlier and after completely cleaning and degreasing the oil level sender, I positively buried the back end of the sensor in MB sealant. That was the easy part. The hard part was waiting for that giant mass of goo to dry. The sealant has tons of surface area to bond to back there, and even gets under and around the wire and sensor electrode so that it could never come off inside the engine. I was still a bit nervous about putting it back in my car.

At any rate, my car has gone from consuming about 1/2 a quart of oil per fill-up to only consuming 1/2 quart after 4 fill-ups. Quite an improvement!

Also notice that casting flaw in the aluminum, right where the o-ring is supposed to seal? Yep, that got gooped too.

Okay, you can let loose the insult and ridicule now....

ps2cho · #2 10-11-2010, 05:49 PM

Why not just replace the sensor? I would be VERY worried about that coming off!!

I replaced my leaking one from the junkyard and not a drip since.

tinypanzer · #3 10-11-2010, 05:59 PM

It was one of those times when I was working on the car late at night, no access to parts, etc. I had gone to all the trouble of pulling it out and draining my oil, so I wanted a solution. I'm sure I'll replace it some day, they are only $50 new. Still, inelegant as it may be, the thing sure is sealed now. Not a drop of oil has leaked past it.

I should have taken a before goop picture. If I had, you'd see that the stuff I gooped over has gaps all the way around it, and that the goop literally surrounds the electrode. Even if it were to de-adhere (is that a word?) from the surface, you'd still have to cut it with a knife to get it loose from the sensor, since it completely surrounds the electrode. Does that description make sense? The goop has formed a "ring" around a metal piece and would therefore have to be cut loose to go floating around in the engine.

RobertFini · #4 10-11-2010, 08:14 PM

The question in my mind is how the "modified" sensor is going to sense the oil level with all that goop in there.

tinypanzer · #5 10-12-2010, 01:20 PM

Take a look at one of those sensors, and you'll see. There are no moving parts where I applied sealant. The float is located in the cylinder below, as are the contacts or reed switch (whatever it is in there). In other words, it works just fine.

Hit Man X · #6 10-12-2010, 04:42 PM

Whatever works, huh?

duxthe1 · #7 10-12-2010, 01:19 PM

When I did my cylinder head I found that someone previously had broken a portion of the rail that holds the upper timing cover "worm" seal. Needless to say when I buttoned it up that seal leaked oil like there was pressure behind it. I pulled it back apart, **** canned the seal and ran a fat bead of the black MB sealer. Well that was about 10k ago and it hasn't leaked any at all...none. Don't think I'm gonna ever use another worm seal again on my own engine.