Wobbly crank pulley (or is it a harmonic balancer?)

[Nader]

Like the title says, this pulley or balancer is wobbly, but not loose. I can't get a good look at it without removing the radiator. I'd like to have an idea of best and worst case scenario about what may cause this before digging in and dumping coolant. Not knowing how it's assembled and attached, I don't know what I'm in for. Engine seems to run just fine. Smooth despite the wobble.

 

[Tireguy87]

The pulley is riveted to the balancer. There is also a "key" that lines the pulley up on the balancer. I had a pulley get enough wiggle in it to start walking on the balancer. As a result, the rivet holes were opened up and the key sheared off. Balancer was fine. I ended up finding a used harmonic balancer/pulley.

I suppose the harmonic balancer nut could be loose, but if that was the case, things wouldn't be running smoothly for very long.

 

[3_puppies]

could you loosen the belts and pry/wiggle and see movement?
at some point you'll need to get to it and get a better look, so you have an idea what is wrong.
you can use a mirror and get a look at the rivets and see if there is evidence of movement.