Diagnose this engine noise?
 

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Heres a quick video i shot of my engine, 1986 NA. When i started it today (actually on the way home, it had only been sitting for about 15 minutes) i got a terrible screeching sound that lasted for about 7 seconds until i got up to speed.

The car has been making a sort of whirring noise since i got it. So i figured id take a quick video and see what more knowledgeable people think it might be. The car is driving fine, no power problems, steering is good etc. I think it might be a fan belt or something.

Anyway the noise in question is that steady pulsing whirring, sort of a mid-high range freq. The previous owner said he recently (within the past 2000 miles) replaced the belts. Maybe they need re-tensioned?

Thoughts

Hard to diagnose without being there, but it sounds like a roller failure. My lower balance belt tensioner sounded roughly like that when it went. If that's it, the sound should be centralized in the black housing mounted on the front of the engine, probably near the bottom. There are 4 potentials in the timing system as a whole (balance belt tensioner, balance belt idler, cam belt idler, cam belt tensioner, cam belt idler). I suppose it could be the bearing set in the water pump as well, but I haven't heard one of those fail, so...

This said, I would expect all these to have been replaced when the timing/balance belts were replaced. No guarantees, but it's considered good practice.

Screeching sound on start up? Definitely could be attributed to a loose belt. I replaced the drive belts and they started screeching before a re-tightening after 1,000 miles or so

Yup only when starting the car. And I noticed it's only when I have the defroster on. Literally the squeal stops when as soon as I turn the defroster off. So it must be something with the pulley on the defroster maybe?

It's the alternator belt that is loose.

When you first start, the battery tries to claw back as much current as it can get from the alternator, usually during the first few second. The air conditioner is just adding to the current draw. The noise is the belt slipping.

After a few seconds, 20-30 it stops because the battery doesn't need 6A anymore, just 2A or so, or you have turned off the air conditioner. The load on the alternator is less, it's easier to turn because it's doing less work, and the friction from your alternator belt is now enough to turn it without slipping.

Cheers
Rissole

Mmm, yep. Consistent electrically-related squeak == alternator belt. Alternator belt squeak tends to get worse as it gets colder (which may include appearing when it didn't exist before).

I have a good condition defroster pulley I am willing to sell cheap.

EPDM belts wear down like tires
 

The alternator belt is a ribbed EPDM belt I believe so wears out by losing material like a tire wearing off tread: EPDM Belt Wear Diagnosis. The point? Even if it looks good it may be worn out (sounds like a belt salesman's dream). Some auto parts stores give out a freeby plastic gauge made by Dayco, Gates or others for serpentine belts. It works like a tire tread depth gauge: Gates Belt Wear Gauge For Serpentine Belts | Gates Corporation.

Defroster pulley--nice joke .http://forums.pelicanparts.com/suppo...leys/happy.gif If the belt is not worn out just tighten it a little; the ideal tightness is just tight enough that there is NO slippage but not so tight that it over stresses the bearings.

Rasta, you're killing me. I have a NOS defroster pulley, never used.