[BeerBurner]

Ok, I've got a mystery noise in my '87 8V na. It's been an inconsistent thing for over a decade but it's becoming more common so I want to look into it.

There is a high pitched noise at about 1.2-1.8k rpm but only during the first minute or two of running. Once the car warms up, it goes away. It is purely engine related and doesn't change if the clutch is in/out, the car is in gear or not, or if the car is driving or not. I only hear it at low revs and during the first bit of driving from cold.

I pulled off the accessory belts to make sure it wasn't any accessories and the noise was still there. It sounds like it's coming from the front but I'm not certain it isn't being transmitted from somewhere else. I put a mechanic's stethoscope around it and it seemed to be loudest around the water pump but the noise went away before I could nail it down (the water pump has ~35k miles on it but the noise predates it).

It doesn't sound like any of the normal failure noises I've come across and maybe it's just some funky resonance from something else. Thoughts?

Thanks!

https://youtube.com/shorts/bu68NepbcAw

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[cmartin]

How hard is it to remove the timing belt cover? My first thought is balance or timing belt tensioner or idler. If its a PITA to get the covers off, a long screwdriver with a plastic gallon jug on the end is a great listening device. Engine belt off is a good idea, safer and fewer moving parts to distract your ears.

[BeerBurner]

It's not too hard and my next step. A full belt retensioning job is maybe 90 minutes so I may just redo all of that anyway.

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[BeerBurner]

I dug into it and the balance shaft tensioner pulley is slightly loose and slightly noisier than the others so I'll go ahead and replace it.* It's a bummer since I did everything less than 15k miles ago (and I've had this noise on and off in the past over several belt changes) so maybe I've just ended up with a bad pulley or two over the years?

Anyway, I'll update this when I replace the pulley. It's not an expensive part so it's worth replacing it for trouble shooting.

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[TurboPooch]

Hard to tell but is sounds like a vacuum leak or a resonance in the AFM. Take the air filter out and the top off the air cleaner and see if it is in there. Another thing to check is the vacuum hoses that go to the thermo valve that is on the right angle water outlet on the back of the head under the intake since it seems to be temperature related. IIRC that valve actuates after a couple of minutes.

[BeerBurner]

Thanks, I'll check in on that after I do the pulley if the noise is still there.

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[BeerBurner]

I replaced the balance shaft tensioner and that wasn't it.* Playing around more with the stethoscope, the only place I could clearly hear the noise is on the water pump body just to the left of the plastic belt housing next to the water pump pulley.* So...* water pump? (I'm guessing so but want to see if anyone has any other ideas before I spend the money!)

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