I am noticing a very low rumble at idle after warm up in my engine...kinda sounds like a dry bearing or something.....doesn't sound like a screaching water pump though....doesn't seem to affect anything.....car runs great and strong....I heard it before I replaced a loose ac compressor belt, too....any one ever have this sound and can recommend what to check???

 

Could it be some bad belt rollers??? You may want to check it out before a roller locks up and takes a timing belt with it.....

 

I should have mentioned that it is a 79 924 na.....