Diesel Car Blowing under bonnet/engine after driving?

[buckaroo]

I have heard of this problem before and its probably nothing to be worried about, but everytime we use our Diesel Audi A3 it blows under the bonnet, after the engine is switched off, and its parked up, blowing away?

Is there a reason for this?
Is it to do with low Oil? or is it a general thing that diesel (Audi's) do? I had one years ago and it did it then (or my wife's did)


Should we be worried, or is there an easy fix?

 

[Munroast]

It will be the DPF cooling down after a regen. Periodically (when driving) they waste excessive amounts of diesel to heat the exhaust system up to stupidly high temperatures, then they waste a lot of electric trying to cool it back down.

Apparently it helps to protect the envirment

 

[foxhole]

It’s not a problem , engine fan runs to cool engine to avoid overheat damage .Many vehicle have this feature .

 

[freddiemercurystwin]

It’s not a problem , engine fan runs to cool engine to avoid overheat damage .Many vehicle have this feature .

It's not that, as mentioned it's the dpf.

 

[foxhole]

It's not that, as mentioned it's the dpf.

The dgf regenerates at every journey ?

 

[johnny2007]

Get the dpf removed and cpu mapped.

 

[Munroast]

The dgf regenerates at every journey ?

on my car it is every 600 miles, but this varies from car to car, some just do it when the DPF starts to create resistance to exhaust flow. Do a lot of fast motorway driving and it may never regenerate, just drive around town and it could be every journey.

My van don't have a DPF so happy times.

 

[Burnerman]

Three possible causes for this......
If the DPF has regenerated the fan stays on to cool down the engine bay;
The radiator coolant temperature may be on the high side;
The air conditioning system may be becoming hot and bothered.
John

 

[freddiemercurystwin]

The dgf regenerates at every journey ?

No didn't see the every journey bit.

 

[foxhole]

Really

 

[foxhole]

I doubt a 10 minute journey would trigger it .

 

[Munroast]

it takes 20 mile or so to complete the cycle, and if your journey is too short it will try and repeat it on the next journey. So it could come on every time. And if you persist with short journeys so it does not get a chance to clear itself, it will bung up, go into limp mode then a very expensive trip to the main dealer or DPF specialist (I have heard £500 mentioned for a forced regeneration)

 

[buckaroo]

it takes 20 mile or so to complete the cycle, and if your journey is too short it will try and repeat it on the next journey. So it could come on every time. And if you persist with short journeys so it does not get a chance to clear itself, it will bung up, go into limp mode then a very expensive trip to the main dealer or DPF specialist (I have heard £500 mentioned for a forced regeneration)

Is this something to be worried about? yes it does do it on small journeys...

 

[Diver Fred]

I have heard of this problem before and its probably nothing to be worried about, but everytime we use our Diesel Audi A3 it blows under the bonnet, after the engine is switched off, and its parked up, blowing away?

Is there a reason for this?
Is it to do with low Oil? or is it a general thing that diesel (Audi's) do? I had one years ago and it did it then (or my wife's did)


Should we be worried, or is there an easy fix?

So in my experience of VW group cars. Cooling fan running (blowing under the bonnet/engine) after switching engine off is one of 2 things; 1) coolant is hot in the radiator and the fan will run until radiator has cooled, Also check the coolant level - is it correct, 2) engine bay temperature is high - any blocked vents or has the under tray been bent up against the car body? Has the coolant been topped up with tap water rather than distilled water or VW approved coolant?
Do you have any amber or red warning lights illuminated in the instrument cluster. Any warnings in the Multi-Function display (the small dot matrix screen between rev counter and speedo). Does the DPF warning symbol illuminate briefly when starting the car? Refer to the handbook. You should see many warning symbols illuminate on first turning the ignition key.
What does the oil temp read in the MFD?

How many miles have you done since the last oil change and how long ago??? Was the oil to VW spec? If you have done under 10,000 miles in the last year I strongly recommend you get the oil changed soonest. The lower the milage the more important to change the oil. Modern oils are high detergent oils and will absorb high quantities of water, low milage will not evaporate the water out of the oil. Oil with lots of water in it will not lubricate properly.

If you have the DPF warning light illuminated or a warning in the MFdispaly then do the following after an oil change if needed. Is the car 5 speed or 6 speed?
Go for a drive - go to the M1 a drive from Junction 21 to Junction 25 and back in 4th gear (5 speed box) or 5th gear (6 speed) keeping the car above 50MPH - that instruction is in the manual. That will help cleanse the DPF.

 

[cdbe]

Is this something to be worried about? yes it does do it on small journeys...

Yes. You should be worried until the DPF warning lights come on, slightly more worried until you can trigger (sometimes manually but often with dealer intervention) a successful forced regeneration - then relieved for a while until the lights come back and then extremely worried until you get the bill for a specialist DPF clean or worst case a complete replacement (possibly a fair bit of what the cars worth at main dealer prices). Then you should have a worry free period depending on your mileage, journey type and remaining time you intend to keep the car.

It's not an exact science but generally, DPF's and short journeys are a recipe for disaster.