Audi 2.5 tdi suddenly sounds like a plane

Hi there i have a 1997 audi 2.5 tdi with 75000 miles and just the other day i was driving the car along the road and it sounds like there seems to be a
loud like fan stuck on and the more you rev it the louder it gets.I use to have many 4x4 ford sierra,s 2.8 and i can recall fitting many viscus coupling,s fans to them.This noise i have on my audi is the same as that or a plane takin of which is noisy and then once it gets up in the sky it the engines backs of to become quiet again well my audi sounds like its keeps takin of or sounds like the choke is stuck on or could it be a sensor.Can anyone please help me it would be much appreciated.
Regards,
John Mann.
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day
a
Is it the 5-cylinder one or the later V6 diesel? I've got the 5-cylinder one, and the electric fan runs all the time as the aircon uses it (don't ask me how or why!), and there is also a viscous fan there. Haven't had that problem on mine - I guess it's just stuck on the fast setting - you'll probably need to replace it if it's that annoying.
Peter -- "The truth is working in television is not very glamorous at all. I just go home on my own at night and sit alone and eat crisps."
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The problem is not the fan or choke or ...
It is a sticking high speed fan relay. Probably in the main relay box on your model.
You need to replace it.
dellboy wrote:

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It happened on VW engines. Oil found it's way from the oil pan vent into the cylinders and kept sucked upward. It makes noise like full trottle. Later they redesigned the vent.
Ronald
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Are you sure it's not speed-dependant instead of rev? If so, and given your mileage I'd bet it's wheel bearings!
JP Roberts

day
a
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