Problem with HttpWebResponse. Does not reply

I hope you guys can help me, I'm having a problem when I try via c # make a request on my server (request is slow, takes about 10 minutes to process and returned)

For fast requests, everything works fine for slow requests (more than 10 minutes) C # does not identify a response from the http server.

The strange thing is that the same code on the server decreases if the loop works, so the problem is c# because I identify in the database that the entire http server cycle has completed and returned

Code:

        Request = (HttpWebRequest) HttpWebRequest.Create( url );
        Request.Method = "get";
        Request.AllowAutoRedirect = false;
        Request.CookieContainer = Cookie;
        Request.KeepAlive = false;
        Request.ContentLength = 0;
        Request.Timeout = 20 * ( 1000 * 60 ); // minutos
        Request.ReadWriteTimeout = 20 * ( 1000 * 60 ); // minutos
        Request.Proxy = null;

        HttpWebResponse Response = (HttpWebResponse) Request.GetResponse();
        Stream ResponseStream = Response.GetResponseStream();
        StreamReader ResponseReader = new StreamReader( ResponseStream );

        bufferResponse = ResponseReader.ReadToEnd();

        Response.Close();
        ResponseStream.Close();
        ResponseReader.Close();

        return ( bufferResponse );

I've tried using the commands:

ServicePointManager.DefaultConnectionLimit = 10;
ServicePointManager.Expect100Continue = false;

And they did not help.