Sharepoint 2013 Search Error

Hi ,

I am getting the following eror while implementing full crawl after changing the hostname.

"Crawling of this item failed, HTTP 504: Gateway Timeout. Try accessing the item using a browser on the crawl machine. If URL is accessible through the browser, it is possible that the crawl targets for that host are not configured correctly"

Can anybody tell me the reson for error.  Thanks in advance

Regards,

Rahul.Poojary