Whenever I upload a new sitemap I seem to fall away in the Google serps. This has been consistent across three of my sites recently. One site that has started to do well had it's sitemap removed about two weeks ago (it was nowhere before!). I read somewhere else that Sitemaps could be a honeypot to trap over eager webmasters. I don't believe this to be true for one minute but don't understand why sitemaps seems to do more harm than good. I would say maybe it's just me but there seems to be quite a few other threads with a similar theme!
I went through the same problem. @ months ago I had opened the site for google to crawl & it started indexing it as normal I got to know about the sitemap & 15 days I submitted the sitemap to google assuming that it will help to index it further. 10 days later all my indexed pages were dropped out..................strange but true......................now they are back. It took over 45 days for google to index my pages as per the sitemap. So I now wonder what is the actual use of a sitemap when google & yahoo automatically index your pages even without sitemap?
Very strange, sitemap shall have nothing with ranking. It will only instruct the spiders to crawl the sub pages.
That's what it should do but if your pages are index & you submit site map to Google then its quite widely reported that you loose all pages from Google, may be submitting site map informs that the site now needs to be crawled differently & crawling takes 45-60 days cycle which is quite some time for many to loose patience.
Sorry this just isn't true, this hasn't happened with any of my sites. Crawling went faster for me after is submitted as i could turn up the frequency.
It’s a rule. If you have a problem with duplicated content or lack of original content on your site; do NOT submit sitemap. Otherwise it will have negative effect.