My 1987 300E has an oil leak. I knew this when I bought it. Apparently it's coming from the timing chain cover/timing box, or someplace similar. I haven't located it myself (not super mechanically inclined) but was told so by a mechanic who was working on my car for a different reason. He said I could just put some silicone there, or JB Weld, and that would seal it right up. Does that sound right to you guys? I'm sure I could attempt that with a friend of mine who's a little more knowledgeable. One thing I've noticed is that there's never any oil under the car, even when it's parked overnight, but it definitely loses oil such that I have to add at least several quarts every 1,000 miles. I honestly don't think it's burning any--not much, at any rate. This brings me to my second question, which is...

While driving, the oil level light comes on intermittently. NEVER comes on at startup, almost never around town, but typically on the highway after cruising at sustained higher speeds for at least several minutes. Even then, it'll stay on for anywhere between 10 sec. and a couple minutes, then go off for a while. Once I return to slower speed driving, the light remains off for the most part. If I check the oil with the engine still warm, sometimes the dipstick will have oil BELOW the minimum mark (near dry). However, if I leave it parked overnight like that and check the oil again in the morning, it'll appear 3/4 full or more. This discourages me from adding more oil (I'll dump in maybe half a quart at most) because I don't want to overfill.

What could be going on here? I thought maybe the sensor was faulty (given my morning oil level checks), but seeing the dipstick almost dry after driving leads me to believe the warning light is accurate. Is it better to check the oil with the engine warm or cold? I always thought you checked the level with the engine cold...but if that's correct then I'd suspect the sensor is crying wolf. By the way, my oil pressure gauge always picks up to "3" when the engine is revved even slightly, and never falls below just above "1". Can the oil pressure gauge tell me anything with regard to oil level?

Of course the oil leak complicates this issue, because I know I always AM losing oil.

 

It sounds like it is draining back too slowly. There could be a chunk of carbon partially blocking the drain hole in the head, where the oil returns to the pan. If you pull the valve cover gasket you can probably check the holes.

As for the leak, if you are leaking several quarts, even 1 quart per 1,000 miles you would see huge puddles on the ground. An ounce of oil on the driveway looks massive. It could be burning it.

I don't think you'd have any luck getting silicone to stick to the surface well enough to seal it. You would have to take it apart, clean it, then seal it.

With these cars you can spend a ton trying to make them perfect and see very little improvement on the whole. There's always going to be something else that it needs. This is just my experience; some say you can spend a few thousand and have a new car again. I have never had the ***** to drop thousands in a German car and see what I get out of it. I just keep up on the maintenance, fix the big stuff, and let the little quirky things go. There are way too many little things to go wrong on such a complex, over-engineered car. Again, just my opinion and I'm not looking for an argument. See my disclaimer.

 

I'm no technical expert either, but I wonder if a faulty filter check valve is playing a part here. Try changing it -- get a proper MB one (they're cheap) -- and see what happens. If you do it yourself, undo it a quarter/half turn and leave it to drain down, and then it won't be so messy a job (tightening torque 20Nm -- hand tight; the MB special tool is only about $20 and well worth buying).

MB's rule of thumb for oil consumption seems to be don't worry too much until it's going at 1 litre per thousand kilometres (about a US quart per 650 miles). "Several quarts every 1,000 miles" seems a bit excessive.

If it's neither puddling under the car nor being trapped in the filter, it must be getting burned. What's the colour of the exhaust fumes like? Perhaps it's a combination of factors, given that the gap between min and max on the dipstick is 2 litres and you're seeing a difference of at least 1.5 litres.

As for sticking-plaster solutions to oil leaks, I wouldn't.

 

If the leak is below the distributor assembly and seeping below the front portion of the exhaust manifold, that would be Front Cover Gasket.
As for the oil indicator, it should come on when your key is the on position then go out as soon as the engine starts. It could be your sensor, located near the oil filter.
For a more accurate result on your oil level, check it after you leave the car parked overnight, and on level surface.
Good luck.

 

The exhaust seems normal--there's no smoke, or really any color/abnormal smell to it at all. I do notice a burnt oil smell through the vents sometimes when I come to a stop after driving on the highway, but I also drove an '86 560SEC where I noticed the same phenomenon, and I didn't have to add oil nearly as often. Maybe it IS burning it, I don't know. However, that mechanic who looked at the car said there is a leak, but for some reason I can't see it pooling on the ground when the car is parked. I got the oil changed today, btw.

The oil level light didn't come on at all today, even on the highway--and that's BEFORE I got the oil changed this evening.

shdoug, I appreciate your comments. I have neither the will nor especially the financial wherewithal to "spend a ton" trying to make my car perfect. I am kind of a perfectionist, but realize that this car is far from perfect--cosmetically and otherwise. It makes neither rational nor economic sense to spend more than I paid for the car (not much) to make it just a little better. It's just something safe, comfortable and [fingers crossed] reliable to get me by for the time being. It's still timeless and solid, and I respect it for that; that's why I bought it. But if I've got to keep dumping oil into it every so often to keep going, I guess I'd rather do that than spend a fortune fixing this moderately annoying issue while something else goes wrong in the meantime. Your point is well taken.

We'll see if anything is different after the oil change. btw I'll check the oil cold now, thanks Lorinser880 for the advice.

RogerJones, thanks for your very specific advice. It's a bit technical for me right now, but I'll refer back to your post if I get a chance to undertake checking the filter check valve.

 

What did you find with the oil level? I just started having the same problem with the oil light coming on during high way driving, never during regular city driving. Then I will slow down or hit a bump and the light will go off.

 

WD, I thought of something else. If you smell oil burning, it could be dripping onto the exhaust manifold and smoking considerably but being drawn underneath as you drive and you don't see it. I was following a car the other day that had a large amount of smoke rolling out from under the car, coming from the engine compartment, but the driver did not seem to notice. You might have someone else follow you around and see if they see or smell any oil burning. If so, the best time to find the leak is when the engine is cold. At least it's not making a mess on the driveway. I hate that.

In my mind, the most important thing is the pressure gauge. If it always reads 3 bar (about 46 psi) when driving then the pump is picking up oil and at least the engine won't be damaged.

BTW, I didn't mean I'm not looking for an argument from you specifically. There are some on this forum who are sensitive and seem to take offense to certain comments. For some reason I tend to evoke their disdain.

 

The filter check valve is embedded in the filter, so it's no more technical a matter than a change of filter. Sorry to have made that less than clear.

 

My car has a leaking head gasket and a leaking front timing cover. They were diagnosed more than 2 years ago and I am still driving without any problems. These are very common or rather I should say these 2 things always happen to everyone with a straight six W124. Leaking and burning are both part of the wonderful experience of owning one of these cars. You do have to be vigilant, however, or you could ignore a big problem that leaves you stranded or destroys your car. Just check all fluids very regularly.

Also realize that there will come a time when you will not be able to ignore these things. You most likely will have to do the head gasket and the front timing cover. With the head gasket, you could end up with oil in your coolant. That is an ugly mess. You could also end up coolant in the oil, or burning coolant and blowing white smoke out the exhaust.

The bottom line is that if you spend all your money on mods, like new wheels, springs, shocks, swaybars, radio head units, speakers, and who knows what else, you may not have the funds to do the head gasket, timing cover, inevitable AC issues that can be absolutely horrible, the water pump every 80K miles or so, the exhaust, or the transmission which will go if you keep the car long enough, and the normal maintenance items like belts, hoses, and regular like fluid flushes.

As for the change in oil level, I think they all change when there is oil splashed up lubricating the engine from recent operation. I would be tempted to drain the oil, fill with the recommended amount of fresh oil, and then carefully make note of the oil level in different situations. Then you could simply add oil to maintain the noted levels in any situation.

 

also what viscosity oil are you using.

ive found that using the wrong viscosity makes the oil pressure gauge read low.

 

OK, I've driven the car to work and back (plenty of higher speed driving) TWO DAYS IN A ROW (total 80 miles since oil change) and the light has not come on once. I think RogerJones was absolutely right about the oil filter check valve. Obviously the filter was changed as part of the oil service, and since then, NO PROBLEMS with the light. Still a little burning oil smell once in a while, but I haven't had to add oil yet.

Thanks for all your comments and advice.

ksing44, I appreciate your wise words. I will buy a decent CD player (currently no radio at all, just a hole in the dash), and the previous owner included some nice 16" 7-spoke rims off the 2001-2003(?) C-Class with the sale. So when I need new tires, I will get some for those rims and put them on the car (the stock wheels are on there right now). But other than that, I'm not planning on investing in any "superfluities" for this car--rather I will drive the hell out of it while I $ave as much as possible for a newer BMW or Lexus (maybe a newer Benz if this car is good to me).

 

I'd take the newer BMW in a heartbeat. I love the 5 series. Avoid the Early nineties V-8, though. BMW has made vast improvements in the last few years while Benz has seemed to go downhill a bit. I have a 2006 X3 that has never been back to the shop once. Granted it only has 9,000 miles but so far, it's as reliable as a Honda or Toyota while being loads of fun to drive. The Lexus puts me to sleep, but it is a very well-built car. Good luck with your plans!

 

shdoug, good to hear about that X3. I like the newest BMW's for all but their styling (compared to 1997-2003 5-Series and 1995-2001 7-Series--my favorites) and electronics (iDrive and all the other things in the 2002- 7-Series and others, which are likely to go very wrong by the time the car is 10-15 years old).

I've had a 1986 528e and 1990 535i (the latter a truly fantastic car, and I don't know why I ever sold it), and am fully aware of the problems with the 1993-1995 Nikasil-block V-8s. Even so, I might risk it with earlier body-style 1993-1994 740's given that I could get one for $2500-3500. That or an early 1990-1994 LS 400, which I know will be smoother and more reliable than anything else, if not as "exciting".

In the end I am shooting for a 1997-2000 540i 6-speed, although I'd be perfectly happy with a 528i, 540i auto or 740i/740iL (1996+). Barring those first choices, I also like the 1992+ S-Class and 1995-2000 Lexus LS 400 (although the latter won't be any cheaper than the aforementioned BMW's, which I'd rather have).

Any experience with any of those models?

 

Only the '99 740iL. It's an amazing car. It handles so well you'd never know it was so big! The owner of my wife's company has owned one since new, and has never had any significant problems other than buying some tainted gas and having to replace most of the fuel system. Not the car's fault, though.

I just drove the '07 535i. It's a twin turbo! It absolutely flies. There's about 1 second of turbo lag and then it just takes off. It redlines almost immediately and the transmission seems to not be able to keep up as it delayed the upshift. It probably just needed some time to get used to my driving because it only had 800 miles on it. It was a very smooth and responsive ride. It almost felt like it was alive rather than mechanical.

 

Wow, that sounds terrific. I can't imagine driving that '07 535i, I think my feelings would be too hurt at not being able to afford it.

I actually did put some significant miles on a '97 740iL, and your feelings on the handling echo mine. On back roads or on the highway cutting through traffic, it feels like an absolute sports car, which sounds preposterous and exaggerated unless one has driven the car. Accelerates like a rocket too. Sometimes I would park it, step out, look back at the dimensions of the car and just say, "Wow." I also drove two '97 528i's, a '90 750iL, '93 740iL, '95 525i and some older BMW's in addition to the ones I actually owned. Also driven my friend's '95 LS 400, a '93 400SEL and briefly a '92 500SEL which had LOADS of problems. Experienced three 1st gen. LS 400's (a '90 and two '93's) but never owned.

So I've got some idea on how the cars drive--that's why I want them--but am always open to more advice/experience on maintenance, stuff to avoid, etc. For example, I've heard the earlier W140 Benzes are prone to a lot of problems (wiring harnesses going bad, shattering double pane glass [experienced] and other stuff--especially electrical).

Pardon me for hijacking my own thread. At least my current oil light problem seems to be fixed.