When I search on google site:site.com it shows I have 2.140 pages on google, but google webmasterTool shows me only 5. What would be the problem?
I think there google webmaster's answer will be correct because it shows number of pages crawled by google.some times site:site.com can give result of other posting of that site.
google can index your 2140 pages and save them in google's database,but the search results when you site:url are not correct,you can check your site map in google webmaster tool.
Don't put too much trust in the numbers shown in GWT, at least not early on. It's quite easy to Google Webmaster Tools in indexed URLs, e.g. just by deleting/readding sitemap. At least you could in the past, I haven't tested it for a while now
In some cases, google webmaster tools are not showing the correct number of indexed url's. I had 2 websites where gwt did not update frequently.
it happen some time crawler don't visit your entire website and how much crawler visit your site that much it will show in cached keep on updating your website pages on regular intervals and it will show you fresh and updated content with page cached