Author Topic: Squealing noise and hunting revs  (Read 798 times)

Offline MrJollygood

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Squealing noise and hunting revs
« 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?

2013 Golf GTI (PP) Tornado Red

1969 Volvo Amazon 122s

Offline MrJollygood

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2013 Golf GTI (PP) Tornado Red

1969 Volvo Amazon 122s

Offline MrJollygood

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Re: Squealing noise and hunting revs
« Reply #2 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...
« Last Edit: 20 June 2021, 15:40 by MrJollygood »
2013 Golf GTI (PP) Tornado Red

1969 Volvo Amazon 122s

Offline Carbon VW

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Re: Squealing noise and hunting revs
« Reply #3 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.
« Last Edit: 20 June 2021, 15:49 by Carbon VW »
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Offline MrJollygood

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Re: Squealing noise and hunting revs
« Reply #4 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.
2013 Golf GTI (PP) Tornado Red

1969 Volvo Amazon 122s

Offline MrJollygood

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Re: Squealing noise and hunting revs
« Reply #5 on: 20 June 2021, 17:48 »
I guess the fluctuating idle would suggest a vacuum leak somewhere...?
2013 Golf GTI (PP) Tornado Red

1969 Volvo Amazon 122s

Offline willni

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Re: Squealing noise and hunting revs
« Reply #6 on: 20 June 2021, 18:18 »
I guess the fluctuating idle would suggest a vacuum leak somewhere...?

How's the seal on the diverter valve?
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Offline madstaff

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Re: Squealing noise and hunting revs
« Reply #7 on: 20 June 2021, 19:46 »
Is the alternator belt jumping about when the engines running??

Could be the alternator freewheel clutch pulley.
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Offline MrJollygood

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Re: Squealing noise and hunting revs
« Reply #8 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...

« Last Edit: 21 June 2021, 12:52 by MrJollygood »
2013 Golf GTI (PP) Tornado Red

1969 Volvo Amazon 122s

Offline MrJollygood

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Re: Squealing noise and hunting revs
« Reply #9 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!
« Last Edit: 22 June 2021, 13:06 by MrJollygood »
2013 Golf GTI (PP) Tornado Red

1969 Volvo Amazon 122s