radiator fan??

Druidbaggie

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Hi,help needed, we have just bought a new octavia 2 ltr diesel, all is well with the car , but noticed the last two journeys of less than 5 miles when i turn the car off there is a fan that keeps running for around 5 minutes then switches off, is this normal or is there a possible problem or am i doing something wrong, any info would be more than welcome
 

The Hood

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If the fans run on after you switch off it means you have interrupted a DPF regeneration. The diesel particulate filter is cleared by raising the exhaust temperature and burning off the accumulated particulates. If you turn the engine off and the fans run on it is because the regeneration is taking place and the temperature has to be lowered. The more frequently this happens the more likely the DPF is to get clogged and that could prove expensive. The dealer or an owner with VCDS can force a regeneration to take place to clear it, but that will not always work.
A modern diesel does not like short runs as it does not get hot enough for long enough. When a regen is taking place the idle speed rises to around 900 rpm, there is sometimes a hot smell and the engine note changes slightly as does the performance but you may not notice all of these things. If you are knowingly going to interrupt a regen try and take the long route and use a gear lower than normal. If you can, take your car for a run along the motorway to let it clean itself. The DPF also accumulates oil ash which does not burn off so always use the correct oil and if you are burning oil that will not help.
 

Druidbaggie

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Thanks for detailed explanation, this is a new car is brand new with only 220 miles on the clock, with lock down at the moment its basically work and back home so journey is around 6 miles one way, how do i know if car is regening are there any warning lights on dash, i'e had a diesel before and understand they need a good clear out from time to time by getting them on the open road and using the lower gears, every when would you think you need to get it on the open road, The only thing i have noticed in the last couple of journeys is the the car is running faster, so at traffic lights its like the choke is on and its running very quick, not sure if this as got any thing to do with it, i'm still learning about car as i've only had car 2 weeks
 
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The Hood

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If the car is fully warmed up when it seems to be running fast (around 900 rpm on idle) that will be when the regen is taking place. However at 220 miles it seems to be rather early. Depending on how mechanically minded you are, there is a phone app (I use android, not sure if it works on apple) called VAG DPF which has a free and paid for version. This reads the ecu via an adaptor that is plugged into the ecu port. It shows the ash content, temperature, how many miles since the last regen etc. The adaptor can be bought on Amazon (look for elm 327, and you get what you pay for).
I have attached a leaflet that explains the DPF.
 

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