1.8T knocking noise from engine (Video)

[Mr G]

So I've just started getting this noise from cold starts. It does it at idle and isn't related to engine speed. Seems to be coming from the drivers side. At first, when the noise started whilst driving it sounded like something had come loose under the bonnet like the washer bottle or something and was knocking against the side of the bay. You can feel the knocking through the pedals. It's less obvious when the engine is fully warmed up.

Any ideas?

In the below clip depending on your speakers it can be difficult to make out. An example is at 28 seconds in where it makes the knocking noise twice.

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p://youtu.be/0Ja7zuJ6HUY

 

[Mr G]

**Update**

It appears to be related to the aircon pump. Possibly the aircon clutch? All I know is that if the engine is idling and I press the aircon button the noise instantly gets worse. Mechanic said you can sometimes get the clutch unit separately otherwise you're looking at serious $$$ for the whle aircon pump unit + regas.

Does anyone know if this sounds about right and or can you get the aircon clutch separately?

Thanks

 

[SlimsLCR]

You could always buy a pump second hand for decent money, ebay is prob your best bet, lots of these cars being broke on a regular basis! plus you can buy a re gas kit for about £30 and do it yourself. My aircon makes a terrible noise too when turned on, but being from Fermanagh I don't need it too often so never bothered about it! Have you ruled out the carbon canister as the cause of the noise before you turn on the aircon! Its located on the drivers side and can make an annoying clicking noise especially at idle that is not engine speed related?

 

[Mr G]

Hi, yeah I reckon eBay might be the way to go however last night it started doing it when I put the rear windscreen heater on so now I'm wondering if it's the alternator. Will check carbon canister, thanks for that.

 

[SlimsLCR]

Yeah, its a bit strange that one! Horrible when you cant figure it out! Good luck anyway bud, if you get it sorted let us know!

 

[L16YDW]

Could be the alternator overrun clutch pulley. You need to pop the belt off to check what's occurring.

 

[Mr G]

Sorry for the dumb question but regarding the belt that drives the AC pump, can you just remove it or does that belt also drive other stuff like the alternator? At work atm so can't check under bonnet. Cheers.

 

[SlimsLCR]

It drives your alternator and power steering pump as well as your ac! It can be taken off breifly if you wanted to try and narrow down a problem. It may possible to get a smaller belt to bypass the ac, but in the long run maybe best to sort ac if its causing problems.

 

[Mr G]

Thanks. Ah that's a shame but to be fair, even if I did it temporarily without the car moving to test if the noise appears it'd be worth it. I'll give it a go.

 

[L16YDW]

I'd put money on it being the alternator at fault.

You could check the air con pump pulley as it sits now. The centre of the pump pulley should free wheel with the engine off, there maybe a little drag on it but should move freely.

The belt can be removed easily, a 16mm spanner on the tensioner. Then spin all the pulleys for smoothness. You could removed the air con pump if you're convinced that's the noise and fit a shorter belt from a non air con model mk4 golf 1.8t. That's what mine is running as mine has the air con removed completely.

I still suspect the alternator decoupler / overrun pulley is to blame.

Where in the UK are you?

 

[Mr G]

Thanks for that. I'll get hold of one of those belts and just take the AC out of the equation.

 

[L16YDW]

You'll need to remove the air con pump from the car to run the shorter belt. I still say the the alternator pulley is to blame. In 12years on the motor trade I've never heard the air con pump make that kind of noise.

 

[Mr G]

Fair enough mate, you know more than me! I'll have a look at it this weekend and report back. Thanks for your help.

 

[SlimsLCR]

I might take mine out too! Its just extra useless weight!lol