Start-up smoke basic question

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xsara92
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Start-up smoke basic question

Unread post by xsara92 »

Hi, is white smoke from a cold engine (petrol or diesel) linked to the engine being under load as opposed to revs?

When I idle my car around the drive, I get a fair bit of the smoke. Engine will be doing only 1-1.5k rpm but under load. However if the car is still and I rev the engine up to maybe 2.5-3k rpm, I don't see the white smoke.

Guessing this is a simple one...
RichardW
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Re: Start-up smoke basic question

Unread post by RichardW »

What does it smell of? It can only unburnt diesel, unburnt oil (turbo seals leaking), or coolant.
Richard W
xsara92
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Re: Start-up smoke basic question

Unread post by xsara92 »

The only word I could use to describe the smell is "sweet".
I'm unsure between oil and coolant. Neither of these has a fresh aroma that I can smell to compare when I stand near the exhaust.
My last HDi exhaust gave the same smell, only stronger. It failed its emissions test badly. There was more white smoke as well.
PaulC5
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Re: Start-up smoke basic question

Unread post by PaulC5 »

Burning fuel produces water and when the engine/exhaust is cold on starting on a cold day you will see steam out of the exhaust but it will stop as it warms up and does not condense in the exhaust. If it continues then it could be unburnt fuel or coolant if the head gasket has failed. If you have Adblue and that has an injector fault then that could give white smoke. If coolant the expansion tank coolant level will gradually reduce.

I had a turbo fail on a petrol Saab on the M6 and that surrounded the car in white smoke out of the exhaust. Before it failed there was blue smoke on starting and on accelerating.
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Rp0thejester
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Re: Start-up smoke basic question

Unread post by Rp0thejester »

1.6 Hdi, smelling sweet out of the back..... Sounds/Smells like coolant to me. If a turbo failure I would expect intermittent acceleration power failure in the turbo range. Has this vehicle failed it's emissions test?
Ryan

'99 Xsara 1.6 X (Red) with Sunkissed bonnet. T59 SBX
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Yes I ask the stupid questions, because normally it is that simple.
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myglaren
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Re: Start-up smoke basic question

Unread post by myglaren »

Probably right but I ran mine on bio diesel for a year and it smelled really pleasant, slightly like alcohol.
xsara92
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Re: Start-up smoke basic question

Unread post by xsara92 »

Rp0thejester wrote: 26 Oct 2024, 22:32 1.6 Hdi, smelling sweet out of the back..... Sounds/Smells like coolant to me. If a turbo failure I would expect intermittent acceleration power failure in the turbo range. Has this vehicle failed it's emissions test?
No but the MOT test is in a few weeks...the Garrett turbo is from 2016, and the car has done 20k miles since that date. Though it could have been installed after 2016. Car passed last emissions test with absorption coefficient of 0.79..
I have had some intermittent acceleration, but the AA found fault codes relating to the crankshaft position sensor, and didn't mention the turbo.
However the last Citroen service was in 2022, so I'm a little worried that an oil change might have been skipped...though the car has only done 2,500 miles in 2 years.
As mentioned I smelt the same thing from the previous 1.6HDi, and that car (though running well) went on to fail its emissions test badly...however, the testing garage did not report any coolant issues or gasket failure, but this could be just a red herring.
xsara92
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Re: Start-up smoke basic question

Unread post by xsara92 »

Thanks PaulC5, I've not seen white smoke from either HDi I have owned when running at speed