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Mercedes Benz S350(2003) - 600SL(1993)
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160 Posts
Discussion Starter #1
Hi there .....
I have a problem. The car runs fine but at slow speed or when its park i notice that there is a black smoke coming out from the exhaust. The engine temperature is fine between the 80C & next line.
Any ID....
 

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Departed 1998 SL500 (and the Pano is in Bogota)
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11,116 Posts
Black smoke usually indicates burning oil.
 

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Sith Lord
72 280SE 88 560SEC 92 E500 6.0 95 SL320 14 GLK350
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11,813 Posts
It could be poor air mixture. Check your plugs and air filter to start with.

You could "smell" the black smoke, it will tell you if it's oil or air.
 

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Mercedes Benz S350(2003) - 600SL(1993)
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160 Posts
Discussion Starter #5
the smell look like CO2
 

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94SL600, 76MGB, 99Suzuki Bandit 1200, 05Yamaha Warrior, 72Triumph Bonnie
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14 Posts
I am having the same issue...once heated up the smoke starts.
I had a compression test and one cylinder showed low pressure, but the car runs perfectly!
I changed a bad MAS, fixed a vacuum hose @ brake booster check valve and the plugs are all clean...
Will a broken cat (which I have) cause any of this???
 

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2011 GLK,2007 S550,2003 S55,2008 CLK,2009 C300,1996 E300,2005 E320,2002 E3
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1,355 Posts
Black smoke is not oil. Black smoke is fuel that has entered the cylinder and hasnt been burned. Blue smoke is oil.
 

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1999 SL500, 2004 CLK500, 2006 Cadillac SRX
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873 Posts
I disagree, blue smoke indicates burning oil, black smoke is an indication of runnin rich. Try cleaning the MAF, changing air filters and check plugs. Also, malfunctioning O2 sensors will cause rich condition to occur. If left too long, it will destroy the cat.
 

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2011 GLK,2007 S550,2003 S55,2008 CLK,2009 C300,1996 E300,2005 E320,2002 E3
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560:
when fuel gets in the oil it can burn black, but usually is related to fuel being dumped in the oil which is usually a problem related to something fuel related(ie injectors etc)
you can usually smell fuel on the dipstick.
 

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1999 SL500, 2004 CLK500, 2006 Cadillac SRX
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873 Posts
560:
when fuel gets in the oil it can burn black, but usually is related to fuel being dumped in the oil which is usually a problem related to something fuel related(ie injectors etc)
you can usually smell fuel on the dipstick.
4benzes - if you look at the times of our posts and what we each said, I think we were saying the samething at the same time - I was not disagreeing with your post, but I will still contend that if black, its rich, and if rich, it's a product of incomplete combustion caused by incorrect fuel/air mixture - which could be injector (leaking by) or MAF sending incorrect signal to the computer which in turn sends incorrect signal, or bad O2 sensor sending incorrect signal, or misfiring plugs or clogged air filter - any which will cause incomplete combustion.
 

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1991 500SL V8 NEOKEN modified T/B. 2000 F350 4x4 V10. 1995 SL500
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201 Posts
Low pressure cyclinder may have a cracked ring on the piston ,which depending on how bad its cracked the amount and color of the smoke and if it's not letting the cyclinder fire correctly product a blacker smoke. Is the car using oil more than normal and running smooth with not even a hint of a skip?
 

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94SL600, 76MGB, 99Suzuki Bandit 1200, 05Yamaha Warrior, 72Triumph Bonnie
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Low pressure cyclinder may have a cracked ring on the piston ,which depending on how bad its cracked the amount and color of the smoke and if it's not letting the cyclinder fire correctly product a blacker smoke. Is the car using oil more than normal and running smooth with not even a hint of a skip?
Concerning the running of the car, yes, it runs very smooth. Oil consumption? I need to check as I have been afraid to drive too much for fear of causing more damage.

I USED to have the gas smell (along with a jerky hesitation) but the vacuum line and MAS replacement fixed that.

The new plugs were running clean even though the smoke condition persists. The smoke starts once the car temp is around 100 degrees...I am wondering if any crap in the "bad" cat has anything to do with it? I'm going to get the free flowing cats put on anyway, so I'll check that.

The (warm) compression test brought the pressure back up a lot (it was 45lbs cold and 165lbs once warm and oiled). The other cylinders were around 193lbs.

I tend to agree with your cracked ring assessment. But I wanted to see if it was something else (wiring issue, CO2, etc.) which may be less costly!

Thanks!!
 

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Mercedes Benz S350(2003) - 600SL(1993)
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160 Posts
Discussion Starter #13
Thanks guys for your answers....
But any one tell me where is the O2 sensor locate. I clean the both MAS's, the air filtters & the spark blugs are prety new ( less than 7000 mile ) but i will change it soon
 

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'97 SL500, 06 Subaru Outback, LL Bean 3.0
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735 Posts
Hi there .....
I have a problem. The car runs fine but at slow speed or when its park i notice that there is a black smoke coming out from the exhaust. The engine temperature is fine between the 80C & next line.
Any ID....
White smoke: White smoke is caused by water and or antifreeze entering the cylinder, and the engine trying to burn it with the fuel. The white smoke is steam. There are special gaskets (head gaskets are the primary gaskets) that keep the antifreeze from entering the cylinder area. The cylinder is where the fuel and air mixture are being compressed and burned. Any amount of antifreeze that enters this area will produce a white steam that will be present at the tailpipe area.

Blue (or gray) Smoke: Blue smoke is caused by engine oil entering the cylinder area and being burned along with the fuel air mixture. As with the white smoke, just a small drop of oil leaking into the cylinder can produce blue smoke out the tailpipe. Blue smoke is more likely in older or higher mileage vehicles than newer cars with fewer miles.

BLACK SMOKE: Black smoke is caused by excess fuel that has entered the cylinder area and cannot be burned completely. Another term for excess fuel is "running rich." Poor fuel mileage is also a common complaint when black smoke comes out of the tailpipe. Black smoke out the tailpipe is the least cause for alarm. Excess fuel will usually effect engine performance, reduce fuel economy, and produce a fuel odor.

How did the fuel get into the cylinder in the first place? Some of the causes of excess fuel are a carburetor that is out of adjustment, a faulty fuel pump, a leaky fuel injector, or a faulty engine computer or computer sensor. If black smoke is present, check the engine oil as in the white smoke example to make sure excess fuel has not contaminated it. Do not start the engine if a heavy, raw fuel smell can be detected in the engine oil. Call your mechanic and advise him of what you have found.

I hope this helps you determine what could be causing your engine smoke, and the possible reasons behind the smoke.
 

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Mercedes Benz S350(2003) - 600SL(1993)
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Discussion Starter #15
Thanks mlrb2113...
Its black smoke, so i think i gonna take it to the mechanic...
 

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1991 500SL V8 NEOKEN modified T/B. 2000 F350 4x4 V10. 1995 SL500
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THe 02 sensors are located on your exhaust system under the car near the cat.
 

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Mercedes Benz S350(2003) - 600SL(1993)
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Discussion Starter #18
i took the car to the mechanic & we diagnose it.
the smoke came from the MAS the airmass reading 0 there is no output at all from both airmass's
 

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'97 SL500, 06 Subaru Outback, LL Bean 3.0
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i took the car to the mechanic & we diagnose it.
the smoke came from the MAS the airmass reading 0 there is no output at all from both airmass's
I suppose that makes it run too rich; not enough air.
Exactly what does an MAF do (if you know & have time)? I'm clueless. I only know that it's one of thousands of things we got that weren't necessary in the '50s and '60s and can't be any more necessary now.
 

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Mercedes Benz S350(2003) - 600SL(1993)
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Discussion Starter #20
I suppose that makes it run too rich; not enough air.
Exactly what does an MAF do (if you know & have time)? I'm clueless. I only know that it's one of thousands of things we got that weren't necessary in the '50s and '60s and can't be any more necessary now.
I Dont know exactly how's the MAS work. But all what i know is that it control the amount of air going to the engine but how dose that go i dont know
 
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