Engine issues?
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AudiWorld Member
Joined: Nov 2008
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From: Los Angeles
No A/C and just normal driving...
but after hearing other people's experiences I guess it is normal...and it's not extremely loud I'm almost sure it happens every time but I can only hear it at home because it's quiet in the garage...interesting "feature"
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Joined: Mar 2001
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It's a save your turbo/anti-coking/anti-sludging feature. The TT has had it for a long time...
About time it came to the A4 as well.
The short version - the turbine bearings in your turbocharger are lubricated and cooled by engine oil and a water jacket. When you shut off the engine the turbine is still very hot since it has been soaking in exhaust gases fresh out of the engine. Engine oil is no longer flowing so the local oil temperatures can increase considerably, possibly to the point of breaking down the oil within the turbo and fouling the passageways around the turbine. This in turn reduces the flow of oil to the turbine during subsequent operation and can lead to a visit from The Turbo Lady (tm). You don't want to meet her.
The after-run coolant pump circulates coolant through the water jacket removing this waste heat and saving the oil within the turbo from overheating. This feature negates the need for turbo cool down idle time and turbo timers. It is indeed a sophisticated luxury car feature.
And it could quite possibly help to extend the life of the engineering plastics and hoses that are used in the engine bay, which is a big plus as well. Heat rot has caused me a lot of headaches with my B5.
The short version - the turbine bearings in your turbocharger are lubricated and cooled by engine oil and a water jacket. When you shut off the engine the turbine is still very hot since it has been soaking in exhaust gases fresh out of the engine. Engine oil is no longer flowing so the local oil temperatures can increase considerably, possibly to the point of breaking down the oil within the turbo and fouling the passageways around the turbine. This in turn reduces the flow of oil to the turbine during subsequent operation and can lead to a visit from The Turbo Lady (tm). You don't want to meet her.
The after-run coolant pump circulates coolant through the water jacket removing this waste heat and saving the oil within the turbo from overheating. This feature negates the need for turbo cool down idle time and turbo timers. It is indeed a sophisticated luxury car feature.
And it could quite possibly help to extend the life of the engineering plastics and hoses that are used in the engine bay, which is a big plus as well. Heat rot has caused me a lot of headaches with my B5.
AudiWorld Senior Member
Joined: May 2008
Posts: 670
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From: Houston
What's changed since the B5 1.8T to make this "needed"? I understand the advantage...
Just wondering why they would include this -- higher cost -- when they used to just put warning messages in the user manual to "avoid spirited driving" for the last few minutes before shutdown...
AudiWorld Super User
Joined: Mar 2001
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A crapload a warranty and service work related to oil sluding is my guess...
For a long period of time the manual recommended synthetic oil but dealerships would often use dino-oil. I know that in my case I dropped off the proper amount of synthetic for them to use in my car during the service visits.
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