Which status-Code to use?

I have a website with several thousand pages of unique content.
Because of some error, about 80% of the content pages in the CMS wont be available for at least one week and just will give back an empty page.
Which HTTP-Status code is correct in this case?

204 = available but no content
302 = moved temporarily (redirect everything to the mainpage)
404 = error with page
503 = server temporarily not available

I thought about using 404 error code and just hope that search egines will index the site again after its online again.
As far as I understand, 503 is only used if a whole webserver is down, not only part of the service?

Kim