I ran into this error at a client in a pretty simple setup, just one WFE and one database server and the error that occurred when attempting to crawl content was:
The filtering process has been terminated. The filter daemon did not respond within the timeout limit.
The easiest way to fix this is to do two things. First ensure that the search service account has access to the SearchIndex share. In order to do this, use the following PowerShell command:
Set-SPEnterpriseSearchServiceInstance -DefaultIndexLocation “[drive]:\Search”\
Secondly, make sure that the WSS_WPG group has access to C:\Windows\Temp
Afterword’s, everything should work great!