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  #1  
Old 11-21-2003, 12:32 AM
wielder of thor's hammer
 
Join Date: Jul 2003
Location: Long Island, NY
Posts: 321
dumb oil burning question

I have an 87 300e it ritually burns oil from somewhere, which I can smell when the economy vent is on. My question is, why does the oil burn? It is mobil 1 0w 40 and it says that it protects up to 400 degrees fahrenheit. Now obviously the oil must be contacting parts of my engine that are hotter than this or it would not burn. However, the temp gauge never goes above 100 degrees celsius. How does it burn? Do certain parts of the engine get hotter than the 400 fahrenheit, possibly the timing chain cover? (appears to be the most likely culprit). Can the area around the oil filler cap get hot enough to burn off oil? I never see oil leaking from it but it appears wet to the eye, yet dry to the touch. Can I rule out bad rings/seals b/c I can smell it through the heat vents?

I don't know, I must be missing something here. Thanks everybody.
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  #2  
Old 11-21-2003, 12:57 AM
azhari
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Is oil leaking from the valve cover onto the exhaust manifold?
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  #3  
Old 11-21-2003, 01:54 AM
wielder of thor's hammer
 
Join Date: Jul 2003
Location: Long Island, NY
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Just went out and took a look, it does appear that there is a small drip coming from spot where the plastic cover and the engine meet, and it is dripping onto one of the six pipes that take the exhaust away from the engine, which I assume is the manifold (sorry, mechanic terminology not a strong point). this small drip has been there since I bought the car, and I never thought much of it because it seemed like such a small amount compared to the amount of oil I am losing (quart every 750 mi). I would always check around and under the "manifold" and see no oil, so I figured the small amount I saw could not possibly be the leak. But now it makes perfect sense that the manifold would burn it off, and this is what I'm smelling. I imagine the leak is the result of a bad gasket, is there a way to confirm this before taking the entire valve cover off?
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  #4  
Old 11-21-2003, 05:17 PM
wielder of thor's hammer
 
Join Date: Jul 2003
Location: Long Island, NY
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this morning I went to check my oil and it was a bit low, but still above the red plastic piece on the dipstick. I added about 3/4 of a quart. When I first turned the car on, I heard clicking (like valves tapping) for about 5 seconds, then it disappeared. If the oil level is o.k. why would the valves be tapping? Could the noise be something else possibly?
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  #5  
Old 11-22-2003, 05:01 AM
wielder of thor's hammer
 
Join Date: Jul 2003
Location: Long Island, NY
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it now seems that oil is leaking from both the valve cover and the timing chain cover, oh boy. still not sure what the clicking was, I will see if it happens again with another cold start.
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  #6  
Old 11-22-2003, 06:17 AM
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Burning oil and clicking....,,,

Hi 'socks'......

Clicking noise on a cold start is usually the hydraulic valve tappets - light clatter before the oil gets pumped up to them......5 or 6 seconds. Only usually noticeable after the car has been standing (say) overnight. Means?......a little bit of wear creeping in and the small amount of oil retained in each of them starts to weep out over time, (welcome to the club :-) ), but might not become an issue for many, many 1000s miles...........keep up oil changes and don't rev too high for first few seconds of running (i.e. until clattering stops).

Oil leak / burning smell - could be a number of things but if its happened suddenly AND you're starting to get leaks all over the place, then try investigating the crankcase breather plumbing. If this gets blocked, the crankcase will pressurise above normal and 'blow' oil out of anywhere it can.

Not necessarily the case in your case but I have had some 'miraculous' fixes for 'orrible oily engines on many makes by clearing the breather system out......usually it must be said on higher mileage cars.

best of luck,

:-)

JH
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  #7  
Old 11-22-2003, 10:11 PM
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Clicking on cold start and an oil leak near the timing chain cover? I'm no expert on timing chain life on an M103 engine. I never had any problem on my 87 300E in 105K miles, but I would immediately check to see when and if the chain tensioner and chain have been replaced. Time would certainly suggest a tensioner replacement and well over 100K miles then the chain is suspect.

After the car has sat for 24-48hrs, open the hood, have some one crank the car and listen for the chain to hit the cover. My MB Dealer calls it "the death rattle". If the chain goes, the valves and pistons kiss and tell, so this is not something you want to ignore.
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  #8  
Old 11-22-2003, 10:45 PM
wielder of thor's hammer
 
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Location: Long Island, NY
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Would'nt the timing chain make noise the whole time the car was running? I would think I could rule it out b/c the noise goes away after a few seconds. Am I correct? Also, wouldn't a timing chain problem cause other differences in engine running besides just noise? (It drives fine otherwise.)
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  #9  
Old 11-22-2003, 11:29 PM
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You may have an air pump(serpentine belt driven) and if so, it's likely above the alternator.

This device can cause alot of racket at first start up in the morning. It's supplying additional air to the exhaust. Compliments of Ralph Nader. The noise it generates usually kicks off about 2-3 mins after the car has been started. This may not be what you're experiencing...thought I'd mention it.
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  #10  
Old 11-23-2003, 12:07 AM
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To answer your question

To answer your question about oil burning.
If and when oil get into the cylinder, ether past the rings or the valve seals,
it will burn. The temps are over 1000 degrees inside the cylinder.
This is almost the only way oil will burn because as you pointed out everything else is sub 400 degrees

-mark
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  #11  
Old 11-23-2003, 12:50 AM
wielder of thor's hammer
 
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if it would only burn in the cylinder, why would I smell it? I figured if it was burning inside the cylinder, the fumes would travel out with the exhaust, and I would not smell it sitting in the car. Is it possible the manifold gets hotter than 400 degrees fehrenheit?
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  #12  
Old 11-23-2003, 01:48 AM
wielder of thor's hammer
 
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I read a post about the car burning the oil till it gets to the halfway mark, but I pretty much ruled this out b/c it will burn the oil all the way down past the min line on the dipstick, with the smell still wafting through the vents the whole time.
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  #13  
Old 11-23-2003, 02:26 AM
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You are right

You are right, on the exterior of the engine the exhaust system gets hot enough to burn oil.
However, if that is what's happening, there will be black deposits left on the exhaust system where the oil is leaking onto it. The oil will not burn off completely .......hope that helps

-mark
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  #14  
Old 11-23-2003, 09:17 PM
azhari
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socks

If it's a leak from the valve cover, it's a shot valve cover gasket.

It costs just a couple of dollars for the gasket where I'm at and it's quite easy to replace for a DIYer...need to get the airfilter housing, cables, etc out of the way before you can get the cover off.

Cheers.
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  #15  
Old 11-23-2003, 11:28 PM
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Oil burning smell is oil on the exhaust manifold, almost always because the valve cover gasket is bad. Replace it, it's easy. Do a search for instructions (or ask, I'll retype them again). Get a new gasket or a new oil filler cap, too -- the gasket shrinks, and oil dribbles out. This can get a as high as a quart in 500 miles and still not leave drips in the drive -- it only leaks at speed.

Peter
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