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dense pale blue smoke, and dense white smoke



The blue smoke is oil, not unusual in a lot of cars, especially
when they first start or have been ticking over for a while and you
pull away. The white smoke is water, usually mixed with oil, this
could be a head gasket but not definately.
Regards, Clive.
Hello Renate,
Diesel exhaust smoke can vary in color and consistency but most can be
classified into four categories according to the color of the smoke.
The first category is blue-white smoke:
Blue-white smoke may be noticed at engine start-up whether the
engine is at normal operating temperature or not. Blue-white smoke can
be observed at all ambient temperatures and should not last longer
than a minute or two after the vehicle has been driven. Blue-white
smoke can return when ambient temperature is below 10 degrees C (50
degrees F), and after the engine is warmed up due to extended
idling. This is due to combustion chambers cooling down during periods
of extended idling time. Heavy blue-white smoke may also occur if the
engine is operated at full throttle with the transmission in neutral
or park. If you see continuous Blue-white smoke while driving, then
you probably have air being sucked into the fuel system.
The second category is white smoke:
White smoke and blue-white smoke share some of the same
characteristics. White smoke is fuel not being burned. Extreme white
smoke can be caused by the combustion chambers cooling down. One cause
of this could be incorrect injection pump timing. Coolant getting into
the combustion chamber can cause white smoke also. Possible causes are
blown head gaskets, cracked heads cavitation, etc.
The third category is black smoke:
Black smoke is caused by an over rich mixture and normally occurs
whenever the engine is working hard. Like going up a steep grade,
being loaded heavy or during heavy acceleration. More black smoke can
be observed when the vehicle is operated at higher altitudes because
the air is thinner. A dirty air filter is also another cause of
excessive black smoke. If black smoke is noticed while the engine is
idling at low altitude or under normal driving conditions this
condition should be diagnosed a.s.a.p. to prevent engine damage.
The fourth category is blue smoke:
Blue smoke is not normal and you do not want to be driving behind a
truck that produces it. Blue smoke occurs when oil is entering the
combustion chamber and is burning along with the fuel. Blue smoke
usual indicates a condition which should be corrected a.s.a.p. Blue
smoke also smells like oil burning. Possible causes include valve
seals or cracked piston rings.
Hope it helps.
Roman (London, UK)
'92 HDJ80
Renate wrote...
Does the white mean blown engine gasket? and blue mean burning other
fluids zas well as the normal fuel? and, is there a difference between
the colours with petrol and the colours for diesel?
Yes Renate you are right.
The white smoke is usually only visible when the engine starts and
the coolant which has been weeping into the cylinder immediately
vapourises. It will normally soon disappear as the engine gets warm.
So if it persists then the leak is getting bigger and the engine is
getting towards terminal failure. Its not only a head gasket but can
also be a crack in a cylinder liner or a crack in the head near an
exhaust port with coolant then entering the cylinder via the valve.
The blue smoke is invariably oil. First via possible poor valve stems
seals or worn stems, but also possibly piston rings. If the smoke
increases in quantity at a noticeable level over a short period of
time then it is more likely a worn piston ring which will eventually
break as its fit in the piston groove gets looser quite rapidly as it
wears. Occasionally a ring can get stuck in the groove with gummy
oil, then letting oil get past and into the combustion process, but
it is a rarity these days. If diagnosed in time then a 'ring free'
oil can be used to free the ring and then keep all the rings working
correctly. An outside possibility can be glazed piston bores which
happens with engines that tickover a lot such as taxis or my canal boat engine.
Both these symptoms will happen on any i c engine no matter the fuel - but...
One other possibility with blue smoke is with a diesel engine when
the injectors need servicing, in terms of cleaning-up the spray
pattern, and there can be a puff of light blue smoke just on
start-up, particularly when the ambient is low. That is a symptom
that can often be cleared by use of a bottle of injector cleaner in
the tank. My old man has maintained the injectors of his diesel Golf
this way since 1979 and never removed them ! (It still achieves 58 mpg). HTH
'92 HZJ80 ex UN Bosnia surplus.
2 cylinder Ruggerini diesel boat engine running on Morris's HDD30
'ring free' oil !!
Tring, Herts
Hi Renate,
If you can see the smoke at idle go round the back and smell it as if it
is blue/white from unburn't fuel it still smells like unburnt diesel so
you can look at injectors or pump problems. If it smells of oil then you
can look at other things. It is interesting to watch 2-3 people standing
round discussing/arguing over what the smoke is when all you need to do
is lean down and have a sniff and it is obvious.
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