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Discussion Starter #1
Right. Am getting royally p1ssed off with this. Having searched both on here and on t'interweb in general I've found a squillion reasons for white smoke from the exhaust, most of which contradict each other :rolleyes:

My mate has white smoke bleching from his exhaust on his 1.8 Mazda from cold start up. It stops once the engine's warm. He also has a raspy leaking exhaust (unrelated to the white smoke, I think, but I like to state all the facts).

From various 'experts' across the web I've read that white smoke is due to:

- coolant getting into the combustion chamber (producing steam)
- oil getting into the combustion chamber
- condensation in the exhaust (producing steam)

Possible causes I've read about are:

- failed head gasket (allowing coolant into the combustion chamber)
- cracked head (allowing coolant into the combustion chamber)
- knackered valve stem oil seals (allowing oil to dribble down into the combustion chamber when the car's sat overnight) - depending on whose version you read, this either a) burns in the combustion chamber producing white smoke, or b) coats the sparkplug, thus impeding the spark and resulting in only partial combustion, and white smoke
- knackered piston rings allowing oil to get into the combustion chamber

Can someone PLEASE point me down the straight and narrow on what can produce white smoke from cold, but stops when warm? I've also read that oil burning gives blue smoke, black smoke and white smoke. Unburnt fuel gives grey, black and white smoke. WTF??? :confused: :chairshot :chairshot

HELP! PLEASE!

My thoughts are that we'll do the following:

-check for chocolatey mayo on dipstick and oil filler cap (head gasket or cracked head)
- check for oil in coolant (head gasket or cracked head)
- remove rad cap, start engine from cold and watch for bubbles in rad (cracked head or head gasket)
- if any of the above, take it to garage for radiator 'sniff test'


Any other ideas on diagnosing what the problem might be?
 

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Discussion Starter #3
He's only just bought the car a few weeks ago. Didn't do it when he bought it but just started now.
 

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it is pretty steamy at the moment, my pug is like a stage smoke machine!

mook
 

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Discussion Starter #5
Yeah - I'm aware that it COULD just be condensation in the exhaust. Will check that his coolant system's ACTUALLY got coolant and not just water in it, then sniff the white smoke to see if it's sweet (have been reading that burning coolant smells sweet). That sound right?

Ironically, symptoms of condensation on the exhaust are white smoke for a minute or so from cold start. Then the condensation has evaporated and it stops.

I've read that symptoms of knackered valve stem oil seals are white smoke from cold start for a minute or so until it clears (as the engine warms the seals expand and seal properly).

So they seem completely indistinguishable, other than the fact that one will see the oil level drop very slightly over time :(
 

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heres a simple one...

does the smoke smell?

burning oil stinks, steam don't ;)

mook
 

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Steam.. My old rover 216GTi TwinCam did it for at least 20 mins because it had quite a large back box which gathered a lot of condensation over night.

If the coolant isn't dropping then don't worry..
 

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From what I know Blue is oil, black is fuel and white is water.

If your losing oil quickly then check its not leaking into somthing else like the coolant and always keep an eye in the rear view for puffs of blue smoke. Or it could be leaking out of a seal onto the floor. Is the engine very oily underneath?

Just to note that some cars can use a lot of oil by design (bad???) for instance the 2 litre Vauxhall DTI engine is terrible for it.
 

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Yea if you have got white smoke from your exhaust its oil getting into the fuel line somewhere, i have had the same problems on past cars.
 

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If the smoke dissapears in the air pretty quickly after coming out of the exhaust it is water.
If the smoke stays in the air for a while it may be oil burning.

For example, if he drives up the road when cold and can see the car behind him it is water, if he cant see the car behind him it is most liekly oil burning :D

As said already, its supprising how much water silencers can hold, let alone any moisture in eth intake.

Rob
 

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Discussion Starter #14
I had a quick look at it for him and general conclusion is that it's condensation. The previous owner modified the exhaust so that instead of running the full length of the body it instead veers off left at 90 degrees and has a small 'Maxy Powah' backbox fitted for a side-exit. No real smell other than normal exhaust gas, no oil in the coolant, no mayo in the oil cap.

Considering a replacement used engine (warranted) is only £250 he's not quite so bothered :)

Cheers for the input guys!
 

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The basics are white for water, blue for oil and black for too rich fuel mixture. Just check the coolant level each week to be sure but water in the exhaust can be usual if the car is only used for very short drives e.g. up the town to do a message etc where the backbox never gets hot. It will lead to a rusty backbox that will lead to holes although :(.

If it is a gasket leak you will see it very clearly if you take the cylinder head off.

A very small amount of oil can cause white smoke by the way.
 
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