How to remove this pancake box?

Question

I know this is a well-trodden question here, but, as per usual, there doesn't seem to be an exact example of the particular fixture that's been previously asked.

I'm trying to install a ceiling fan where only a light fixture used to be hung. I removed the light fixture to find this pancake box in the ceiling.

This building is 100 years old, though I don't know how old the fixture is.

I was able to remove the 1" nuts from the holes where the wiring is coming out. I was also able to remove the two screws holding the box into place. There are also two metal stubs coming out of the box still; I'm not sure if they are nails or rivets, but they are loose and would not prevent the box from coming down.

The problem is, I can't figure out how to get the box out of its current hole. It seems to fit perfectly into the plaster/drywall. I've sprayed some blaster (to get those nuts off) and also around the edge, and I have tapped with a flat-head screwdriver around to get rid of some excess plaster, but it's not looking like it will budge.

Any advice?

Edit based on comments:

• The light had a ground wire connected to one of the screws, though, admittedly, it was barely attached.
• I was not planning on changing the wiring. It's an apartment in a multifamily building, so I don't have access to the ceiling or walls.
• The fan does have a light. I was planning on controlling the fan/light with pull chains. The fan (Westinghouse Comet) has explicit two-wire connection instructions, but I may be out of my depth.

At this point I could put the old fixture back on and give up, call an electrician, or keep trying to pull out that pancake box and put on a stronger box for the fan.

Answer 1

Don't remove it.

As you said you're renting I'm going to answer for a few different scenarios.

1. If the landlord or super or manager is able/willing to take this on, you should get their help and in many jurisdictions you must do that in rented place rather than do DIY electrics. So the rest of this answer applies to either that person or to you, depending on what's permitted.
2. If there is NOT a joist behind this junction box I think you'll need landlord involement as you will need to break open more of the ceiling to install a proper fan box that uses nearby joists for support.
3. If there IS a joist above this, I guess it would run from about 1:00 to 7:00 in your picture you should simply reattach the cable and ground to the box as they were before, attach the fan bracket directly to the joist using wood screws of appropriate length, and drilling through the box if necessary or convenient. Attach the ground wire using a third screw and leave enough of it to attach the lamp's ground wire to it with a wire nut. Use the chains for control as you said.

If you're lucky it'll be #3. The strategy is, use the joist not the box to directly support the fan.

You should also put a metal cap in the unused breakout at top right.