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'98 C280 Water-in-Oil Problem(?)

2910 Views 13 Replies 6 Participants Last post by  lugnut2099
So, crap. Went to check my oil this afternoon, saw a bit of the signs of water in the oil. Opened the filler cap, as nasty-looking as you could get. First thoughts were of course that it's screwed, but then I got to thinking - it runs great, it doesn't knock, it doesn't get hot, it doesn't smoke, the oil/coolant levels don't seem to be off, etc. Then I started googling stuff and found a lot of mentions of M112 engines with this issue in cold weather/short trips caused merely by condensation and a poor design and now I'm convinced this must be what's happening, but not sure. The oil itself doesn't seem milky or anything, just a tell-tale sign of something askew. The dipstick doesn't have any of the "peanut butter" goo on it that you see under the cap.

Anyway, it had admittedly probably been a month since I'd looked at the oil by stick, but it was fine then. I'd checked via the dashboard method last week and got an "OK." These past couple weeks though, it's been pretty damn cold (below freezing) in the mornings/nights, and the car does get used for a lot of short trips. Now while *I* let the thing warm up, neither my wife nor my friend who lives us seem to understand how to do this. Incidentally during these past couple cold weeks, I've let our friend use it in the morning to take her kids to school a mile or two away, since her car has no heat and a bad power steering fluid leak. It's still very cold then, she goes there and back, and then the car sits for around another three hours before I go to work.

My drive to work is about 16 miles, so really the engine is probably *just* getting to the normal temp at that point (in this cold weather), I'm thinking, right? From there, the car generally sits for 8 hours again, and it's night by the time I get home and thus, cold as hell again. Drive the 16 miles home, car gets shut off, usually sits 'til the next morning or maybe a very short trip to the store inbetween.

Soooo.... does this sound to you guys like the condensation issue? It seems that way to me, but I'm far from mechanically inclined and might just be wishful thinking. I'm just betting with the cold snap the thing's probably never quite getting warm enough to burn it off, especially after reading how common this seems to be, but I dunno. If it was head gasket/head/block I'd think I'd surely be experiencing some kind of issue with the performance or some kind of dashboard error light triggered or something, but it's just fine seemingly and even though ever since I've been *looking* for something wrong (I'm a pessimist by nature, heh), I still can't think of any unusual symptoms... other than the nasty gunk under the cap. I'm going to go ahead and change oil/filter this weekend, but I almost have to wonder if I might be wasting money/time doing so.
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Yeah, definitely gonna give it a good lookover when I change the oil Sunday. One more thing I thought of - during some of these especially cold days/nights, I've taken my lunch at work and just sat in the car with it idling to get some heat and avoid staying out of the building while I can. Obviously it's a waste of gas and probably not exactly "good" for the car in some way or another, but it's never been more than 15 minutes or so. Anyway, I did it today just to see what temp it gets to in that time frame after sitting for a little over four hours, and during that time it never quite got to the 80c mark. So would those little idling excursions be likely to have added to a potential condensation problem as well, or should it not make a difference?

The worrying thing is that, about two weeks after I bought this car, the water pump locked up (not surprising since it turned out it looked to be the original one). I was maybe 1-1/2 miles from home and didn't have many other options except to try to get it home asap, but wasn't too concerned since I figured I could get there quick enough to not hurt anything too bad. Well, it got hot fucking quick. Apparently enough to blow the radiator at the hose connector (though it never actually fully pegged the temp gauge). Yikes. Figured I was screwed then and there what with the alum block/heads and that would be all she wrote for the Benz, but we got the parts, crossed our fingers, and everything seemed to be fine. That was back in July, and I've never seen this problem 'til now... so if damage had truly been done to the heads or the heat had shrank the gasket, wouldn't this have shown itself months ago?

But like I said, I really don't know shit from a mechanical viewpoint, so I appreciate any input!
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Well, did the oil/filter change today and...

Nothin' wrong with it. Oil was good, filter was clean. Worth the cost just for peace of mind really I suppose. Not sure why it wasn't getting warm enough to burn the crap off, but that sure seems to have been the problem. Will be keeping a close eye on it this week, since it's supposed to be pretty nice the next few days before the next cold snap hits, so will be interesting to see what it does. I'm guessing it'll be fine then do it again when it gets cold.

(And man, makes ya wonder how many people have paid for new head gaskets when perhaps they didn't need to after all...)
I recommend if you havent done plugs in a while, replace them, and when you do, inspect them well to get an idea of the cylinder condition. That will tell the tail more as much as oil will. Also, check the antifreeze. If you see an oil slick in the top of the bottle, you have a leaking head gasket.
The plugs were done back in July, but yeah, never did pull one the other day to look at IT. Antifreeze was fine, though. Like I mentioned in last post, was gonna keep an eye on it all week - drove it like usual, checked every day from Monday-Wednesday when temps were in 50s-low 70s, and everything was fine and no buttery gunk under the filler cap. Today the high was about 24 and, far as I can tell from the extended forecast, appears like it will remain as such for about the next seventy-two years or so. Now to see if it starts gooing up again...
Just to update, after that aforementioned cold spell, I checked it again when it warmed up - yep, goo was back. Not nearly to the extreme amount that was there when I first started the thread, but back nonetheless. Checked the oil again though, and no signs of water at all. Coolant looks good too.

So what the hell? Heh. This week it's been pretty warm and the goo hasn't accumulated again, so it's almost certainly got to be the condensation issue, but why doesn't it burn off? Like Aquinob said, once mine gets to 80c it basically stays there and that seems to be the normal temp for these, so I'm not really understanding what's causing it.

(Incidentally, since this seems to be a known problem, could running 87 octane somehow contribute to the problem? I get 91 when I can and try to throw some booster in when I have to do the 87 - or just forget and hit the wrong button on the pump like I did last night - but I was indeed running 87 mainly back in November when I first noticed the problem and it looked *really* nasty, but had mainly been running 91 since then and the goop this past time was nowhere near as bad as the time last month, so now I'm curious...)
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Y'know, I'm honestly not positive this time around. I know the first oil I'd put in it was Castrol Syntec, but when we changed the oil this past go-round my old man had decided to buy it for "an early Christmas gift" and after draining the 'old' oil out and seeing it looked clean, I wound up getting a phone call and going back inside and in the meantime my dad had already replaced it. I *think* it was Havoline Synthetic, but yeah, not sure.
lugnut, have you come across this thread:

Do your deposits look worse (if that's even possible) than those of the threadstarter? You don't have to read through all the pages, by the way: in the end, nothing was wrong with his engine, as many predicted (although some others vigorously argued his head gasket was blown...).

If you still worry, why don't you take your car on an extended joyride--1-2 hours on the highway--and see what happens.
Nah, hadn't seen that particular thread but did see another one that looked almost as nasty (and also turned out to be fine). That looks only a little worse than mine did back on Thanksgiving day when I posted this thread, though. (Most recent time wasn't nearly as bad.) Only seems to do it in cold weather though, since after Thanksgiving we had a week or so where temps were in 60s-70s and I checked every day and no signs of it. Once it got cold again, the goo came back. Like I said before, it's about a 16-mile drive to/from work, so you'd think it would get warm enough to burn it off, but...

Still, I don't think there's a thing wrong with it. Oil and coolant seem fine, filter was clean when changed after the Thanksgiving incident, car runs/drives great, no other symptoms associated with head gasket-or-worse problems. But jeez, what a terrible design flaw.
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