White smoke from exhaust - Not head gasket issue issue (with pics)
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Junior Member
Joined: Dec 2020
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From: Athens Greece
C200 W203 2.0l
White smoke from exhaust - Not head gasket issue issue (with pics)
Hello dear members. I am extremely worried for the following issue. Light white smoke is coming out of my exhaust.
I noticed it a couple of days ago.
I have also checked cooling fluid, oil filler cap and spark plugs for signs of head gasket failure but seems NOT to be a head gasket 
(as can be seen from the photos).I also hear little noise from i think the catalytic converter (like its cooling down when the engine is running though or cracking...???)
The car is a W203 Coupe 2.0 petrol (2001) 163bhp M111.955 engine with auto/sequential gearbox.
I really hope its a bad catalytic converter issue or a bad
white residue on exhaust
no mustard inside the cams
no white on spark plug i.e. not a head gasket issue
coolant level not dropping and no bubbles
knocking from catalytic converter
fuel injector and not some kind of a crack on the engine.
(this comes from some research i ve done).Can you please send your thoughts / estimates about it ?
I really appreciate your time and thank you !
Senior Member
Joined: Apr 2009
Posts: 317
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w203cl
Usually the M111 gets a crack in the head gasket at cyl 4. You can see water running down the engine above the gearbox or water enters the combustion chamber on cyl 4. So, the head gasket failure is not excluded. Try to see some differences at the sparkplug from cyl 4. The better option is to pressurize the coolant reservoir and see if you loose pressure.
(I would probably try to fix it with a water additiv for leaking head gaskets first if you don't have water in the oil)
(I would probably try to fix it with a water additiv for leaking head gaskets first if you don't have water in the oil)
Thread Starter
Junior Member
Joined: Dec 2020
Posts: 19
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From: Athens Greece
C200 W203 2.0l
@112233 thanx for your reply. but as you can see there is no drop in the coolant level and the spark plugs are all in the same condition. which one is cyl 4 ? the one towards the windshield or the other towards the front bumper ?
Thread Starter
Junior Member
Joined: Dec 2020
Posts: 19
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From: Athens Greece
C200 W203 2.0l
Usually the M111 gets a crack in the head gasket at cyl 4. You can see water running down the engine above the gearbox or water enters the combustion chamber on cyl 4. So, the head gasket failure is not excluded. Try to see some differences at the sparkplug from cyl 4. The better option is to pressurize the coolant reservoir and see if you loose pressure.
(I would probably try to fix it with a water additiv for leaking head gaskets first if you don't have water in the oil)
(I would probably try to fix it with a water additiv for leaking head gaskets first if you don't have water in the oil)
Senior Member
Joined: Apr 2009
Posts: 317
Likes: 49
w203cl
yes cyl 1 is at the front. The typical cat failure is an internal crack of the catalytic ceramic. The parts block the exhaust gas exit a bit with engine power loss. I'm not sure if it is connected to white smoke. Does the smoke has an odor? If its cat related it should have some, unburnded fuel, rotten eggs or so.
I don't know how long do you have the car, but the exhaust of the coupe produces a lot of water vapor compared to the sedan. I guess its related to the very big end muffler which has a larger cooling effect (?)
I don't know how long do you have the car, but the exhaust of the coupe produces a lot of water vapor compared to the sedan. I guess its related to the very big end muffler which has a larger cooling effect (?)
Thread Starter
Junior Member
Joined: Dec 2020
Posts: 19
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From: Athens Greece
C200 W203 2.0l
@112233 i do hear a ticking - cracking noise from inside the catalytic converter like its cooling down but constantly. the smell i get is like exhaust gases. definitely no cooling fluid smell.
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