Removing/Adding a server to query role:

Removing a server out of query role:
- Stopped Office SharePoint Server Search from App server, it should take Problem server out of query role or Clicked on the service Office SharePoint Server Search from the problem server and remove the check box to take it out of the query role. 
- If Stopping it from CA result in error, Error from event logs. and follow the below steps
- Checked events logs and didn't find anything
- Pausing all active crawls from CA.
- Checked the service Process ID from TASKlist command by executing it from the farm admin account. 
- Kill the service from kill /f mssearch.exe.
- Checked from services.msc that Office SharePoint Sever Search is in disable state and from task manager.
- Deleted everything inside E:\index\'Guid ID for index folder' on the server to clear the space, which is having problem.
- Start the crawls.

Adding a server out of query role: 
-  "STOP Timer Scripts Service
- Once  timer service script is stopped. Proceed to add the server to query role.
- In the Service column, click Office SharePoint Server Search.
- On the Configure Office SharePoint Server Search Service Settings page, in the Query and Indexing section:
- Clear the Use this server for indexing content check box.
-Select the Use this server for serving search queries check box.
- Click Start. Then configuration of the application server as a query server is now completed.
- Confirmed from services.msc that service is in start state.
- Need to wait untill the index propegating gets finished if you have another query server in the farm. Watch SSP for the status.
- Once propagation finishes, restart timer services.
- Resume the stopped crawls.