How to diagnose good vs bad pulley bearings?? (1 Viewer)

[Kernal]

I started to dig into the oil pump cover O-ring and crank seal replacement job and noticed the idler pulley seems to have a very slight amount of noise/grinding when spun (only noticeable if held an inch from my ear); it sounds like the bearings need grease. I have another less used idler pulley that is smooth and has no noise at all, but when I spin it it stops within two seconds compared to seven seconds for the one I just pulled off. I realize we can run without this pulley but I plan on putting one of them back in; question is which one is more likely to be good? The top photo shows the idler pulley as I found it with what looks like old grease which had leak from the seal.

Found about the same thing for the AC belt adjuster pulley; old grease around the seal and a very slight noise when held close to the ear. This bearing is replaceable being held in with a snap ring; it's number is NSK 6301DU2; anyone know if this bearing is available through Toyota? I searched the internet and found a Timken bearing (301SS) apparently of the same size/type that's available for around $16. The bottom photo shows the AC adjuster pulley (cleaned up) with the snap ring removed.

 

[-Spike-]

Dry bearings free-spin much longer than greased bearings. Noise/grinding is bad.

 

[Kernal]

Spike: that's exactly what I was thinking, less drag from no grease, been a long time since I compared good vs bad side by side. Looks like the bearing in the idler pulley is not replaceable short of drilling out those twelve small rivets to separate the two half-shells.

I probably should have added "--- and water pump bearings" to the title; found that my water pump squeaks when I rotate it by hand left or right and it seems to have a tad of play but it's not leaking, yet. Interesting though, I have a known bad (leaking) water pump from another vehicle on the shelf and it rotates smoothly with no noise or play.