White smoke cloud from exhaust - causes?

Hi all,

I have a 2012 Passat Highline diesel estate and today noticed a large cloud of white smoke in my rear view. This was just after turning a corner, going up a slight incline, probably in 3rd gear. I've noticed it happen a couple of times before in the past say around six months, both times when going up hills.

I've read that white smoke can mean an issue with the head gasket and relates to the coolant leaking, but I've checked the coolant level and it doesn't appear to be going down. I've also checked the oil which appears to be fine. Fuel consumption is normal too.

Can anyone suggest what else this may be? It isn't a continuous white smoke, literally a burst and that's it. The previous couple of times was when it was colder, and not long after starting the car, and I assumed it may be from where it was cold, but today this happened at the end of a short journey.

It has roughly 150k on the clock, and no noticeable performance issues. No warning lamps or messages. It's been doing long 400 mile plus journeys say every other weekend with no issues.

Does anyone have any ideas of what this may be??

Thanks.

Read any codes?
Sounds like it does it under load. ?? turbo oil seals letting a bit of oil past on occasion.

short journeys and cold weather sounds like normal water vapour as seen from any exhaust in cold weather when the exhaust is not quite up to temp

Yes - all three times when going uphill. Car wasn't full of stuff or towing but they're not exactly nimble in themselves anyway.

If it was a coolant leak issue/head gasket problem would I expect to see the smoke a lot more?

I thought maybe where the engine was cold on start-up as the first two times was at the start of a journey, and yesterday the end of a short journey (say five miles), however when I've seen this vapour before it seems to be a continuous flow coming out which then disappears, whereas this is a cloud of white smoke and that's it.

I thought oil issues created black smoke? (But then I don't know too much!)

I haven't had any codes come up. No warning lamps etc. The vehicle has a DPF but does get a good run every few hundred miles to burn off. If the filter was filling is this something that could create the smoke? (I'm thinking this can't be it though as it did a motorway run the other weekend...)

Myself & my wife both have Passats with the 2l CR engine.
Both do this on occasion, always when going fairly slowly ( up to 40 mph ).
It is always associated with the engine doing a DPF regen.

The ECU decides when to regen the DPF, this could be during a motorway journey or on the very next journey around town.

We have got used to this peculiarity.
Both cars return excellent MPG & use no oil or coolant so we just live with it.

Basically if you're using no excessive oil, no coolant and the MPG is good, i wouldn't worry too much. Maybe get a scan to see if any codes are stored.

Thanks all.

Had to pick a tyre up today and had a chat with the person in the garage and have booked it in for a free once-over to see if they can see any issues. Only worried as doing the long journeys at the moment and don't want to end up on the side of the road (even though I have breakdown!) Will keep checking the levels regularly and post back for info if there's any result from the check.

Quote:

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Originally Posted by philipharmes

Myself & my wife both have Passats with the 2l CR engine.
Both do this on occasion, always when going fairly slowly ( up to 40 mph ).
It is always associated with the engine doing a DPF regen.

The ECU decides when to regen the DPF, this could be during a motorway journey or on the very next journey around town.

We have got used to this peculiarity.
Both cars return excellent MPG & use no oil or coolant so we just live with it.

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Mine, a PD engine with 205k on the clock does an ACTIVE regeneration every few hundred miles despite a 14 mile each way commute of 50 / 60mph short bypasses and 40mph A roads. My previous work location was 34 miles each way starting slow, then a 15 mile dual carriageway, 40/50mph A road followed by a 5 mile motorway stretch which was always enough for passive DPF regeneration. To clarify the difference the regeneration type is as follows:

Journeys too short or slow for the engine to raise the DPF temperature to burn the soot in the DPF into ash means the ECU invokes an ACTIVE regeneration by closing the EGR valve if still fitted, injecting extra fuel post main injection which ignites on the exhaust cycle thus increasing the after turbo exhaust temperature and that inside the DPF and as a side effect often spueing a cloud out the back for the 8 to 10 minutes needed to complete the process.

If the journeys are long and / or fast enough (revs over 2000 for most of the time) the exhaust gases emitted are naturally higher and reach the in DPF temperature level needed to burn the soot into ash WITHOUT closing the EGR or adding extra fuel. This is PASSIVE regeneration.

Older cars may shove out a lot of bluish white smoke on an active regeneration being a little unburnt fuel and oil vapour from oil build up in the intake and cylinders (the higher combustion temperature tends to burn off more in engine deposits).

So the garage plugged it in for a scan but no error codes had been logged. They said if it keeps happening I could take it to the more specialised VW/Audi independent in the nearby town (not sure what they would do extra though if no codes logged?!). Going to assume this is a DPF regen-related thing for now - from what's been suggested it sounds quite similar - and just make sure I keep an eye on the oil and coolant levels as needed. Still on the long journeys and getting expected MPG and not happening all the time so happy to monitor for the time being.

Quote:

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Originally Posted by tommytink

So the garage plugged it in for a scan but no error codes had been logged. They said if it keeps happening I could take it to the more specialised VW/Audi independent in the nearby town (not sure what they would do extra though if no codes logged?!). Going to assume this is a DPF regen-related thing for now - from what's been suggested it sounds quite similar - and just make sure I keep an eye on the oil and coolant levels as needed. Still on the long journeys and getting expected MPG and not happening all the time so happy to monitor for the time being.

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One thing to add - regeneration merely burns larger soot particles collected in the particulate filter into tiny ash particles that are retained by the DPF ever increasing in volume. By 120k the DPF may be nearing capacity and thereafter heading towards a full state at a later mileage. 150k is enough for the filter to have reached capacity at which point it needs removing and either cleaning or replacement. Following either of these events the ECU will need to be told the new or refitted cleaned filter is once again empty (otherwise the car will think the DPF is still full and may adjust running parameters based on false data).