I have a tomcat app that was working without problems for months. But suddely (I dont know why) it started to fail. Why? It loads and old version of this app. I created a new .war, I reinstall tomcat but is still loading the old version.
How can I solve it?
Tomcat will only run what you give it: it won't resurrect phantom .war files.
Per your comments, the Tomcat is not in a production environment - everything's apparently all on your workstation. So Jenkins (or equivalent) isn't an issue.
SUGGESTION:
Eclipse > File > Switch Workspace > Other > "workspace-new"
Eclipse > Window > Show View > Server > Servers > Define a new Server
For example, your new instance might be under
%USERPROFILE%\workspace-new\.metadata\.plugins\org.eclipse.wst.server.core\tmp1\wtpwebapps
Eclipse > File > Import > Import existing project ...
You should NOT see an "old version".