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Discussion Starter #1
Hi guys
Can anyone tell me what the hunning noise is that comes from under the bonnet when you switch off your engine ..it normally runs for about 25 seconds
or is it just my spooky van
thanks
ps its a 07 plate t28
 

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i aint a mechanic but my astra used to do it and i think ,i said think ! it was a sticking n75 valve :*:*
hope i got that right
 

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Same model, same year, mine does it. It's too timed to be a fault and it's not intermittent. It's something running over on purpose I think.

Dunno what it is though. Overrunning water pump sounds good though!
 

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I was lead to believe that the noise is a pump which circulates water around the engine and also part of the turbo to prevent the oil in the potentially red hot turbo from burning or damaging the turbo bearings ( a problem on a lot of early turbo cars ).
Some of the highly tuned Jap turbo cars have auto engine run on's to do the same job..
 

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Discussion Starter #11
So Its the water pup cooling the turbo and its ok to leave or is it the turbo valve sticking they are both feasible and if its the valve does anyone know how much they cost to fix
just like to say feedback has been excellent from everyone and great to know mine isnt the only one doing it cheers everyone*<:)>
 

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For your own peace of mind next time you pull up disconnect the N75 and see if the noise stops.
 

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Discussion Starter #15
definitely the n75 martyn i felt it today as i switched off engine it was vibrating ..will it cause any damage if left thanks
 

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This valve is responsible for controlling the movement of the pneumatic actuator which drives the wastegate. The wastegate is an internal valve in the turbo-charger which controls the amount of exhaust gas that flows over the turbo impeller generating boost. Under normal operating conditions the engine's ECU sends signals to the N75 valve asking it to open or close which adds or reduces pressure on the wastegate actuator which results in more or less boost. The question is, is the valve faulty or is it receiving a signal from the ECU when it shouldn't. Either way, I can't see it doing any damage, especially when the engine isn't running. I would try and get it on VAGCOM to see what fault codes it throws.
 
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