Unable to delete Stale mongo data

I have a db with a collection of images with no references and the size has increased to about 160GB.
Now I am not able to delete any records as any operation times out. I have multiple instances of files, which can be queried. But the delete many and any other operation times out.

Pleas help

May be it is doing collscan
Are you using index on the fields from your query.Check explain plan

Check this link