[Markymark12345]

Hi. Just bought a 11 plate vw t5 t28 with 75k, When I switch the engine off there's a loud humming noise that lasts at less 10 seconds. I know sustain vehicles do make these sort of noises due to fuel pumps or throttle bodies etc. But this humming is quite loud and goes on quite long. I'm just asking you guys is this normal or do I have a problem and need to ring the garage where I bought it from and get them to sort it. Thanks

 

[BitterandTwisted]

Morning Markymark and welcome ,
Buzzing...how loud are we talking ? From under the bonnet ?
Theres no noticeable buzzing from our van .
Maybe i'll double check that later ....

 

[Bennymassive]

If it sounds like a mini jet engine it is an auxillary diesel water heater (not fitted to all models).

 

[ZuluGolfZulu]

It could be the so-called ‘moo’ valve on its way out. Proper name is N75 valve. Makes a kind of fart noise for a few seconds after switching off. Happened to my T5 in 2019, part cost 50 quid ish, plus VAT.

According to the VW independent garage dude, it’s quite a common problem. The valve is part of the vacuum control system and leads to problems when it goes completely.

Good luck with it, anyway

 

[transparu]

It's not the fan running on, is it?

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[Markymark12345]

Fan is switched off. Wheres the location of this n75 valve, And how do I find out if the van has a auxiliary diesel water heater, And thanks for the quick replies

 

[Bennymassive]

Aux heater is under the van, near side, behind the passenger seat. You should be able to see a small exhaust pipe underneath the van about half way (you can see it better from the off side). On a T5 the N75 is fairly central in the engine bay, at the top, underneath the dash. Might be different for 5.1. If it is the N75, it could be the valve or hoses, or both.

 

[T5 TDI]

Any chance of a video? Hard to describe a noise. The fact that it does it after switch off limits things. The N75 noise is like a honking mooing sort of a noise which lasts for a few seconds only. It is on the bulkhead.

 

[transparu]

The fan can and does run after the engine is turned off. In my van it's not loud, but sounds like a hum. It only comes after engine is quite warm and then switched off.
In my case the moo valve sounded exactly like a moo - I don't know cows that hum, but they do moo. In my experience, that sound only lasts about a second and almost always is whilst the engine is running. It is very audible inside the van.
FWIW.
Have someone else turn off the engine whilst you have the bonnet up and head close. That might help locate the noise location. Fan is in front of the radiator. Moo valve is centre top of the engine bay under the sill and wiper mechanism.
Hope that's a step in the right direction.



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[Markymark12345]

Tried to upload video but wont let me, message says The uploaded file is too large for the server to process. Basically sounds like a humming sound that's lasts about 10 seconds and gradually goes quieter and then just stops sound like it's coming from the bulkhead somewhere.

 

[DoubleA]

Could it be a vacuum pump for the brake servo?

 

[Markymark12345]

Van doesnt have auxiliary heater and it's not the fan, noise does seem to be coming from back of engine near the top it's making a few clicking sounds aswell. I use to have a Hyundai ix35 that use to make this noise and got told that its self cleaning the flaps on the inlet manifold but that was so much quieter than than this. Maybe it's just me not use to it

 

[Markymark12345]

Will have a look at the vacuum pump tomorrow

 

[LarryM]

The coolant fan can run on for some time after the engine is switched off?

 

[Scorpionv8i]

Could just be the auxiliary coolant pump located near bulkhead that will run on after engine switched off if it’s needed, that makes a low humming sound that lasts more than 10 seconds.