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Model specific boards => Golf mk7 => Topic started by: MrJollygood on 19 June 2021, 12:15

Title: Squealing noise and hunting revs
Post by: MrJollygood on 19 June 2021, 12:15: Just driven half way across the country (done about 600 miles in the last 24hrs) without skipping a beat (and with 40mpg average!) and get to the top of my street and the car starts making a loud squealing noise - sounds like a belt slipping. At the same time the engine is hunting at idle, almost like it's pulsing...

...any ideas?
Title: Re: Squealing noise and hunting revs
Post by: MrJollygood on 19 June 2021, 13:28: https://photos.app.goo.gl/amrBhYqGUQjuiGUZA (https://photos.app.goo.gl/amrBhYqGUQjuiGUZA)
Title: Re: Squealing noise and hunting revs
Post by: MrJollygood on 19 June 2021, 13:33: Waterpump? Fanbelt? Not sure what would cause the revs to hunt like that though? Wondered if anyone had encountered similar...?

EDIT: Started it up just now, squealing has disappeared but the revs are still bouncing around and the (according to the manual) 'catalytic converter' warning light has lit up...
Title: Re: Squealing noise and hunting revs
Post by: Carbon VW on 20 June 2021, 15:45: If the cat warning light is illuminated, then the cat is either not working as intended or is overheating. Can you scan the car for codes ? I would be very cautious with this light on and would get it checked as soon as. You could do damage to the cat which is going to lighten your wallet. Is the car standard or modified ? My first check would be on the EGR valve system, which might explain the Rev hunting.
Title: Re: Squealing noise and hunting revs
Post by: MrJollygood on 20 June 2021, 17:10: Thanks for the reply. It's booked in at my local indy tomorrow so will hopefully find out the issue after a scan. Car is completely standard.
Title: Re: Squealing noise and hunting revs
Post by: MrJollygood on 20 June 2021, 17:48: I guess the fluctuating idle would suggest a vacuum leak somewhere...?
Title: Re: Squealing noise and hunting revs
Post by: willni on 20 June 2021, 18:18: Quote from: MrJollygood on 20 June 2021, 17:48
I guess the fluctuating idle would suggest a vacuum leak somewhere...?

How's the seal on the diverter valve?
Title: Re: Squealing noise and hunting revs
Post by: madstaff on 20 June 2021, 19:46: Is the alternator belt jumping about when the engines running??

Could be the alternator freewheel clutch pulley.
Title: Re: Squealing noise and hunting revs
Post by: MrJollygood on 21 June 2021, 09:54: Thanks gents - will take a look...sounds like it could be one of many things, hopefully it's not too painful to diagnose and remedy...

Finger crossed it's not the turbo letting go...will update the thread when I know what the problem/solution is...
Title: Re: Squealing noise and hunting revs
Post by: MrJollygood on 22 June 2021, 13:02: Thanks to those that replied. Just for future reference incase it helps anyone else - the issue seems to be the PCV breather valve. The mechanic diagnosed it in about 10 seconds. Apparently the squealing / whistling noise is the diaphragm letting go. Key signs are increased oil use, fluctuating revs and the fact that with the engine running it's almost impossible to open the oil filler cap due to the increased pressure. Replacement was only about £70 plus an hour's labour so not too painful!
Title: Re: Squealing noise and hunting revs
Post by: Carbon VW on 23 June 2021, 20:10: Glad you got it sorted. What mileage are you at just for reference to keep a good eye for oil leaks in and around the PCV unit and to recognise the symptoms you detailed.
Title: Re: Squealing noise and hunting revs
Post by: MrJollygood on 24 June 2021, 21:41: 79,500.

Reading about the PCV it seems they are designed to last 80,000 miles... :laugh:
Title: Re: Squealing noise and hunting revs
Post by: Carbon VW on 24 June 2021, 22:37: Thanks for that info. My car is also a 2013 model but I have over 100,000 miles. Might look in replacing it myself before I suffer your fate !! :angry:
Title: Re: Squealing noise and hunting revs
Post by: MrJollygood on 28 June 2021, 09:39: Anything else you've had go that's worth noting?

I had the fuel pump start leaking (!) at around 70k and the front DCC shocks at around 55k
Title: Re: Squealing noise and hunting revs
Post by: Carbon VW on 28 June 2021, 14:44: Engine coolant temp sensor most recently. And thermostat housing replaced at approx 70k miles. Also a sensor on the intake manifold.