Pros & Cons of deindexing a site prior to launch of a new site on the same domain.

[medtouch]

If you were launching a new website to completely replace an older existing site on the same domain, would there be any value in temporarily deindexing the old site prior to launching the new site?

Both have roughly 3000 pages, will launch on the same domain but have a completely new url structure and much better optimized for the web.  Many high ranking pages will be redirected with 301 to the corresponding new page.

I believe the hypothesis is this would eliminate a mix of old & new pages from sharing space in the serps and the crawlers are more likely to index more of the  new site initially.

I don't believe this is a great strategy, on the other hand I see some merit to the arguments for it.

[tylerfraser]

No! Do not deindex your site.

There's something to be said about not doing everything at once. If you see lots of bad pages that will not be used and can not be redirected then let them go to 404. I think this is recommend on account of panda and only having good content and not redirecting bad content to good content. But you are losing link juice.

[MikeTek]

If you've set up 301 redirects for the important pages (those with links or that get direct traffic from bookmarks, etc), I would simply let the old pages fall out of the index on their own.

Just be sure those old pages are properly returning a 404 status. When Googlebot requests a page and gets this server response, it will deindex the page.

If the old content is problematic for sensitive reasons, you may want to request removal of specific pages - this will stop them from being accessible in Google's cache. There is no other benefit here, and unless there is truly sensitive information or some legal reason to remove those pages, requesting removal of those pages is not worth the effort. It won't help the new pages get indexed faster.