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C5 x7 regeneration, blue smoke in engine bay?

harrisson_citroen

Thank God for my Hydroen
Came back home after a 50 K drive, when back in the garage, smelled the pungent usual smell of the generation in progress.
However on lifting the bonnet, a thin Blue smoke came up from the back of the engine. That's worries one. Anyone knows if it to be expected during a regeneraton?
 
During a regeneration the exhaust gets bloody hot. In fact it is recommended that the procedure be done on a stone or concrete floor base. It could be the regeneration combined with road grime or "normal" oil spray has become so hot as to burn off stuff on the outside of the entire exhaust system. A forced regeneration is not a pleasant process to observe, The engine will idle to normal operating temperature then sit at about 4000 revs for up to 20 minutes, It is my understanding that when the sensors ( one upstream of the diesel particulate filter and one downstream of the DPF ) decide there is no pressure differential between the two ( ie the filter is no longer clogged ) it will just return to idle speed and all should be well. I would think no panic yet. A diesel revving without load at those revs is not a pleasant noise. Hope this helps.
 

Ken W

1000+ Posts
If that happened to me, I would get the car out driving again ASAP. I have heard that some Italian Diesels had a light on the dash to tell you when it was doing a regeneration. That would be handy to tell you to keep driving until it goes out.

Cheers, Ken
 

harrisson_citroen

Thank God for my Hydroen
Ken, why would you drive it again? To see if it does it again? Or complete the cycle?
Am a bit worried with light smoke which I haven't seen on previous regeneration cycles.
 

harrisson_citroen

Thank God for my Hydroen
During a regeneration the exhaust gets bloody hot. In fact it is recommended that the procedure be done on a stone or concrete floor base. It could be the regeneration combined with road grime or "normal" oil spray has become so hot as to burn off stuff on the outside of the entire exhaust system. A forced regeneration is not a pleasant process to observe, The engine will idle to normal operating temperature then sit at about 4000 revs for up to 20 minutes, It is my understanding that when the sensors ( one upstream of the diesel particulate filter and one downstream of the DPF ) decide there is no pressure differential between the two ( ie the filter is no longer clogged ) it will just return to idle speed and all should be well. I would think no panic yet. A diesel revving without load at those revs is not a pleasant noise. Hope this helps.
Thanks M.Fritz, yes I'm aware of the regeneration process of the dpf, and know it gets extremely hot.
The burnt rubber smell when in progress is very noticeable, but this is the first time I have seen smoke with it. Wouldn't like to be in the centre of Brisbane at peak hour with my car on fire....
 

Ken W

1000+ Posts
I would keep driving it to complete the regeneration cycle. Come to mention it, mine did smell a bit hot recently when I was driving it. I just thought it must have been a car close by as all the gauges were normal but it could have been doing a regeneration. I have seen on somewhere in Diagbox (the BSI log file maybe) that it records when each regeneration occurs and tells you how many km ago this happened.

Cheers, Ken
 

harrisson_citroen

Thank God for my Hydroen
Yes, that's what I mean, but I think it'll have to be at dealers under controlled conditions.
As you must know it's pretty hard to see anything behind the engine while looking from above.so I'm hoping they can from underneath. Cause there's no way I'm driving it like that!
 

harrisson_citroen

Thank God for my Hydroen
Forgot to add that the smoke clearly came from behind the engine between the shiny insulation mat and the block. Very light blue, suggestion more like oil based.
 

Ken W

1000+ Posts
Run the car up on ramps, add side stands to guard against suspension collapse and slide in from the front with torch and see if there is any wettness on the back of the engine. I usually have very black oil drips on my turbo heat shield.

Cheers Ken
 

seasink

1000+ Posts
I had an oil mess once from the vacuum line coming off the doseur. The oil ran down and under the engine. The line was very loose when replaced. I'd do as Ken suggests, though the under tray will need removing for a good look. For jobs like this I also use a small sheet metal backed mirror that was my teen-aged mother's, so a century old. Waste not etc.
 

harrisson_citroen

Thank God for my Hydroen
Thanks for all the leads, guys. I'll be investigating all this on Friday when I take it to the dealers, as there is fire risk involved.
I can't remember whose Aussiefrogs member's C5 X7 it is that burnt totally in a garage next to the house a few years ago. Could be a similar issue that hadn' t been detected in time.
 

harrisson_citroen

Thank God for my Hydroen
It was thought that the fire started due to an electrical short in the engine bay - so different issue.
Thanks Ken, I thought there was still a shadow of a doubt as to how it all started .
With mine, everything is pointing to a leak at the back of engine
Will know more on Friday and post here.
 

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