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imaparana

Humming noise on lupo gti

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Hi all, 

ive recently done the cam cover gasket, timing belt and water pump on my gti.

all went fine and drives great still, however at idle above say 95degrees (on obd2 reader) there is a weird humming noise that comes on and off, when the fan kicks in and cools it down the noise goes away.

at first I thought it may be vvt related but would do it with the plugs disconnected on the cam cover.

its possible it’s always done it and never noticed it before.

any ideas?

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I think you need to stand over it and watch when the fan kicks in - you previously mentioned an off - could it be damage in the front panel allowing the fan to be off axis till it gets up to speed?

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On mk2s and many other vdubs, the cooling fan motor bearings can run dry, and they sometimes make an odd hooting sound and vibration when hot. Actually a bit like the owl sound we all get in our Lupos from the interior heater fan motor.... Might be related to the cooling fan motor exactly like @LR5V suggests.

It's not cam belt related is it? Too tight? Unlikely as you know your stuff 😀

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cheers all for the comments and suggestions

the noise happens before the fan comes on, (say 5degrees before) 

i dont think its cambelt related as it goes away when rev'd and only happens at temperature and goes away once the fan has cooled the engine down.

As ive got all the time in the world because of this lockdown im going to tear it all down again and redo the job...

will keep this updated

thanks all

 

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Only thought of cam belt, because the thing gets tighter as the engine heats up. You know what a too tight cam belt sounds like- is it like that? Just wondering if some sort thermal expansion is creating a wierd situation somehwere...

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Good thinking on the belt I hadn’t considered that it gets tighter as everything expands,

I’ve taken the whole lot apart again and done the rocker cover gasket to and have the exact same issue with the same symptoms (what a waste of a day), I even took the water pump out to make sure it looked and felt good.

so yea all back together and same noise 

it goes away the minute you raise the revs, even by the tiniest amount

ive tried the screw driver to ear trick with no luck

stuck for ideas now, other than it being a bad part I’ve put on (pulleys,pump or belt). 

open to ideas

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Here is a video (hopefully)

 
I know the cam solonoid is disconnected, this was done to rule it out

Edited by imaparana

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Is the stupid arrow pointing where it should precisely on the timing belt pulley?

That's my 2p on it.

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3 minutes ago, Rich said:

Is the stupid arrow pointing where it should precisely on the timing belt pulley?

That's my 2p on it.

Indeed on both pulley, both times round. I rechecked after a few full rotations 

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That just sounds like the coolant fan blade touching something -at least its very doing it gently.  

Its difficult to look at as its within the panel - have you checked the fan is secure and the fiberglass supports solid?

Edit - loving the Gold heat wrap

Edited by LR5V

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9 hours ago, LR5V said:

That just sounds like the coolant fan blade touching something -at least its very doing it gently.  

Its difficult to look at as its within the panel - have you checked the fan is secure and the fiberglass supports solid?

Edit - loving the Gold heat wrap

The fan isn’t on when the noise is there unfortunately 

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I wonder if it's a vibration rather than something rubbing. I had a similar problem with one of my SDIs... took me a while to figure out- ended up being the upper cam belt cover edge vibrating against the head. Found by pressing and leaning on everything in the engine bay until it stopped. Solution was removing it, bending it out of shape a bit and replacing again. Fixed.

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UPDATE: Noise has gone...

I don't know what it was as it was there after i redid everything, but its gone. im not going to waste any more time on it as it runs fine.

If it comes back i may investigate further.

Thanks for all the input.

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