Loud metalic noise when cold

[diesel_lv]

'67 Coronet w 496. Running a serpentine pulley setup. At start up when engine is cold, not actually temperature, just hasn't run that day, it has a very loud metalic noise. Similar to a bolt rattling around in a timing cover. Scared me to death. Removed belt and started engine. No noise. So not something in engine. All accessories including w/p are driven by same belt w a belt tensioner. Water pump has a bushing style bearing? What about alternator, a/c, p/s? I'm pretty sure tensioner has round, roller type bearings. W belt off and spinning by hand, w/p spins smoothly and doesn't come to a quick stop so I don't think it is making the noise. Any suggestions? All others feel smooth, but they all have some sort of internal drag. The tensioner does not freewheel, it stops spinning in under a one revolution. Don't want to replace components trying to figure it out. Once engine has run for about 5 minutes, noise goes away. Thanks in advance.

 

[wagonman]

Sounds like a belt chirp issue. When I worked at a gm dealer we had problems with the PS pulley alignment, it would chirp and sounded like a knock sort of. Gates made or still makes a lazer that sits on the ps pulley to align with the crank pulley. Then either press the ps pulley in or out to align. Don’t take much.

 

[vance.dykes]

get a stethoscope and put it on a bolt near each pulley there will be a growling noise if bad a woush sound if good.
it could be the a/c clutch as the lock up over time the clearness change and can make noise when disengaged.

 

[diesel_lv]

get a stethoscope and put it on a bolt near each pulley there will be a growling noise if bad a woush sound if good.
it could be the a/c clutch as the lock up over time the clearness change and can make noise when disengaged.

Ya, kinda reminds me of a/c compressor clutch noice. Very difficult to zero in on exactly where it comes from. Definitely not belt chirp. Unfortunately it's a brand new, not refurbished, a/c compressor from Rock Auto. It's for a '95 Durango. Noise is not rhythmic at all, very intermittent but persistent until it's run about 5 min. Very loud, can hear w hood down over engine noise, even inside the car.

 

[BLK 68 R/T]

Is the compressor engaging like it’s trying to run the A/C? I had a bad ground on my compressor and it was chattering when trying to activate the clutch. Ran a ground wire from the compressor body to good ground and problem solved.

 

[vance.dykes]

Ya, kinda reminds me of a/c compressor clutch noice. Very difficult to zero in on exactly where it comes from. Definitely not belt chirp. Unfortunately it's a brand new, not refurbished, a/c compressor from Rock Auto. It's for a '95 Durango. Noise is not rhythmic at all, very intermittent but persistent until it's run about 5 min. Very loud, can hear w hood down over engine noise, even inside the car.

ok over time the clutch will grove the clutch and pulley face the clearance on most is 0.20 inch.
when it is making the noise engage the clutch and see if the noise stops.

 

[diesel_lv]

Is the compressor engaging like it’s trying to run the A/C? I had a bad ground on my compressor and it was chattering when trying to activate the clutch. Ran a ground wire from the compressor body to good ground and problem solved.

No, I've watched it and it doesn't appear to be trying to engage. And it goes away after about 5 minutes. Kinda as if a set of bearings had finally gotten lube.

 

[Belle66]

Maybe an exhaust leak, I struggle to tell the difference between that and valve tapping form too much lash.

 

[Slap Stick]

The tensioner pulley should spin freely.

 

[diesel_lv]

The tensioner pulley should spin freely.

I was thinking that. But didn't have anything to compare it to. It won't turn a full revolution, like the bearings are gummed up.

 

[diesel_lv]

Maybe an exhaust leak, I struggle to tell the difference between that and valve tapping form too much lash.

Nothing metalic n non rhythmic about an exhaust leak.

 

[BLK 68 R/T]

I was thinking that. But didn't have anything to compare it to. It won't turn a full revolution, like the bearings are gummed up.

I would say that’s the likely culprit.

 

[diesel_lv]

I would say that’s the likely culprit.

I'm gonna check n see if I get the noise tomorrow by starting it and immediately turning on a/c. Then go to parts store n see if the have a tensioner in stock, if so see how it spins. Hopefully it's the tensioner. Much cheaper than having a/c evacuated and buying new compressor.

 

[Slap Stick]

You did say the noise stopped when the belt was removed.

 

[33 IMP]

I have had nothing but trouble with the factory 80s stuff that i had , that had mono belts. I have had to replace everything those damn monobelts drove (water pump, smog pump, alternator, a/c compressor, )on both a five liter mustang and a big block chevy pickup. But the only trouble ive had with my diesel with the mono belt was when one of the idlers(there's two) siezed, and the belt got major chewed up. Every chance i get, i replace the idlers on monobelts. (And keep a spare new belt, and the wrench to change it, in the car.)

 

[diesel_lv]

You did say the noise stopped when the belt was removed.

Yes, no noise when belt is off. That makes it accessory related. Tried it w the a/c on and it still does it but less than w it off. That's making me think it's a/c compressor related.

 

[Slap Stick]

But the tensioner pulley wont spin. Turning on the ac puts more pressure on it.
Your eyes and test of the pulley are telling you its the pulley. Don't overthink it.