diff --git a/.travis.yml b/.travis.yml
index 7824d9b39..8f37e2997 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -11,7 +11,7 @@ env:
   global:
     - GO15VENDOREXPERIMENT=1
   matrix:
-    - ES_VERSION=2.4.4
+    - ES_VERSION=2.4.6
   allow_failures:
     - go: tip
 before_script:
diff --git a/CONTRIBUTORS b/CONTRIBUTORS
index 459c2382b..6bce05cf7 100644
--- a/CONTRIBUTORS
+++ b/CONTRIBUTORS
@@ -10,18 +10,21 @@
 Adam Alix [@adamalix](https://github.com/adamalix)
 Adam Weiner [@adamweiner](https://github.com/adamweiner)
 Adrian Lungu [@AdrianLungu](https://github.com/AdrianLungu)
+alehano [@alehano](https://github.com/alehano)
 Alex [@akotlar](https://github.com/akotlar)
 Alexandre Olivier [@aliphen](https://github.com/aliphen)
 Alexey Sharov [@nizsheanez](https://github.com/nizsheanez)
 AndreKR [@AndreKR](https://github.com/AndreKR)
 Andrew Dunham [@andrew-d](https://github.com/andrew-d)
 Andrew Gaul [@andrewgaul](https://github.com/andrewgaul)
+Arquivei [@arquivei](https://github.com/arquivei)
 Benjamin Fernandes [@LotharSee](https://github.com/LotharSee)
 Benjamin Zarzycki [@kf6nux](https://github.com/kf6nux)
 Braden Bassingthwaite [@bbassingthwaite-va](https://github.com/bbassingthwaite-va)
 Brady Love [@bradylove](https://github.com/bradylove)
 Bryan Conklin [@bmconklin](https://github.com/bmconklin)
 Bruce Zhou [@brucez-isell](https://github.com/brucez-isell)
+cforbes [@cforbes](https://github.com/cforbes)
 Chris M [@tebriel](https://github.com/tebriel)
 Christophe Courtaut [@kri5](https://github.com/kri5)
 Conrad Pankoff [@deoxxa](https://github.com/deoxxa)
@@ -31,8 +34,11 @@ Daniel Heckrath [@DanielHeckrath](https://github.com/DanielHeckrath)
 Daniel Imfeld [@dimfeld](https://github.com/dimfeld)
 Dwayne Schultz [@myshkin5](https://github.com/myshkin5)
 Ellison Leão [@ellisonleao](https://github.com/ellisonleao)
+Erwin [@eticzon](https://github.com/eticzon)
 Eugene Egorov [@EugeneEgorov](https://github.com/EugeneEgorov)
+Fanfan [@wenpos](https://github.com/wenpos)
 Faolan C-P [@fcheslack](https://github.com/fcheslack)
+Filip Tepper [@filiptepper](https://github.com/filiptepper)
 Gerhard Häring [@ghaering](https://github.com/ghaering)
 Guilherme Silveira [@guilherme-santos](https://github.com/guilherme-santos)
 Guillaume J. Charmes [@creack](https://github.com/creack)
@@ -54,6 +60,7 @@ John Stanford [@jxstanford](https://github.com/jxstanford)
 jun [@coseyo](https://github.com/coseyo)
 Junpei Tsuji [@jun06t](https://github.com/jun06t)
 Kenta SUZUKI [@suzuken](https://github.com/suzuken)
+Kevin Mulvey [@kmulvey](https://github.com/kmulvey)
 Kyle Brandt [@kylebrandt](https://github.com/kylebrandt)
 Leandro Piccilli [@lpic10](https://github.com/lpic10)
 Maciej Lisiewski [@c2h5oh](https://github.com/c2h5oh)
@@ -71,6 +78,7 @@ Nicholas Wolff [@nwolff](https://github.com/nwolff)
 Nick K [@utrack](https://github.com/utrack)
 Nick Whyte [@nickw444](https://github.com/nickw444)
 Orne Brocaar [@brocaar](https://github.com/brocaar)
+Pete C [@peteclark-ft](https://github.com/peteclark-ft)
 Radoslaw Wesolowski [r--w](https://github.com/r--w)
 Ryan Schmukler [@rschmukler](https://github.com/rschmukler)
 Sacheendra talluri [@sacheendra](https://github.com/sacheendra)
@@ -85,6 +93,7 @@ Tetsuya Morimoto [@t2y](https://github.com/t2y)
 TimeEmit [@TimeEmit](https://github.com/timeemit)
 TusharM [@tusharm](https://github.com/tusharm)
 wangtuo [@wangtuo](https://github.com/wangtuo)
+Wédney Yuri [@wedneyyuri](https://github.com/wedneyyuri)
 wolfkdy [@wolfkdy](https://github.com/wolfkdy)
 Wyndham Blanton [@wyndhblb](https://github.com/wyndhblb)
 Yarden Bar [@ayashjorden](https://github.com/ayashjorden)
diff --git a/client.go b/client.go
index 63844406f..3879baec1 100644
--- a/client.go
+++ b/client.go
@@ -799,8 +799,12 @@ func (c *Client) sniff(timeout time.Duration) error {
 
 	// Start sniffing on all found URLs
 	ch := make(chan []*conn, len(urls))
+
+	ctx, cancel := context.WithTimeout(context.Background(), timeout)
+	defer cancel()
+
 	for _, url := range urls {
-		go func(url string) { ch <- c.sniffNode(url) }(url)
+		go func(url string) { ch <- c.sniffNode(ctx, url) }(url)
 	}
 
 	// Wait for the results to come back, or the process times out.
@@ -811,7 +815,7 @@ func (c *Client) sniff(timeout time.Duration) error {
 				c.updateConns(conns)
 				return nil
 			}
-		case <-time.After(timeout):
+		case <-ctx.Done():
 			// We get here if no cluster responds in time
 			return ErrNoClient
 		}
@@ -822,7 +826,7 @@ func (c *Client) sniff(timeout time.Duration) error {
 // in sniff. If successful, it returns the list of node URLs extracted
 // from the result of calling Nodes Info API. Otherwise, an empty array
 // is returned.
-func (c *Client) sniffNode(url string) []*conn {
+func (c *Client) sniffNode(ctx context.Context, url string) []*conn {
 	var nodes []*conn
 
 	// Call the Nodes Info API at /_nodes/http
@@ -840,7 +844,7 @@ func (c *Client) sniffNode(url string) []*conn {
 	}
 	c.mu.RUnlock()
 
-	res, err := c.c.Do((*http.Request)(req))
+	res, err := c.c.Do((*http.Request)(req).WithContext(ctx))
 	if err != nil {
 		return nodes
 	}
@@ -974,37 +978,55 @@ func (c *Client) healthcheck(timeout time.Duration, force bool) {
 	conns := c.conns
 	c.connsMu.RUnlock()
 
-	timeoutInMillis := int64(timeout / time.Millisecond)
-
 	for _, conn := range conns {
-		params := make(url.Values)
-		params.Set("timeout", fmt.Sprintf("%dms", timeoutInMillis))
-		req, err := NewRequest("HEAD", conn.URL()+"/?"+params.Encode())
-		if err == nil {
+		// Run the HEAD request against ES with a timeout
+		ctx, cancel := context.WithTimeout(context.Background(), timeout)
+		defer cancel()
+
+		// Goroutine executes the HTTP request, returns an error and sets status
+		var status int
+		errc := make(chan error, 1)
+		go func(url string) {
+			req, err := NewRequest("HEAD", url)
+			if err != nil {
+				errc <- err
+				return
+			}
 			if basicAuth {
 				req.SetBasicAuth(basicAuthUsername, basicAuthPassword)
 			}
 			if c.prepareRequest != nil {
 				c.prepareRequest((*http.Request)(req))
 			}
-			res, err := c.c.Do((*http.Request)(req))
+			res, err := c.c.Do((*http.Request)(req).WithContext(ctx))
 			if err == nil {
+				status = res.StatusCode
 				if res.Body != nil {
-					defer res.Body.Close()
+					res.Body.Close()
 				}
-				if res.StatusCode >= 200 && res.StatusCode < 300 {
-					conn.MarkAsAlive()
-				} else {
-					conn.MarkAsDead()
-					c.errorf("elastic: %s is dead [status=%d]", conn.URL(), res.StatusCode)
-				}
-			} else {
-				c.errorf("elastic: %s is dead", conn.URL())
-				conn.MarkAsDead()
 			}
-		} else {
+			errc <- err
+		}(conn.URL())
+
+		// Wait for the Goroutine (or its timeout)
+		select {
+		case <-ctx.Done(): // timeout
 			c.errorf("elastic: %s is dead", conn.URL())
 			conn.MarkAsDead()
+			break
+		case err := <-errc:
+			if err != nil {
+				c.errorf("elastic: %s is dead", conn.URL())
+				conn.MarkAsDead()
+				break
+			}
+			if status >= 200 && status < 300 {
+				conn.MarkAsAlive()
+			} else {
+				conn.MarkAsDead()
+				c.errorf("elastic: %s is dead [status=%d]", conn.URL(), status)
+			}
+			break
 		}
 	}
 }
diff --git a/client_test.go b/client_test.go
index a33e46137..1f2ab6f79 100644
--- a/client_test.go
+++ b/client_test.go
@@ -10,12 +10,15 @@ import (
 	"errors"
 	"fmt"
 	"log"
+	"net"
 	"net/http"
+	"reflect"
 	"regexp"
 	"strings"
 	"testing"
 	"time"
 
+	"github.com/fortytw2/leaktest"
 	"golang.org/x/net/context"
 )
 
@@ -264,6 +267,74 @@ func TestClientHealthcheckStartupTimeout(t *testing.T) {
 	}
 }
 
+func TestClientHealthcheckTimeoutLeak(t *testing.T) {
+	// This test test checks if healthcheck requests are canceled
+	// after timeout.
+	// It contains couple of hacks which won't be needed once we
+	// stop supporting Go1.7.
+	// On Go1.7 it uses server side effects to monitor if connection
+	// was closed,
+	// and on Go 1.8+ we're additionally honestly monitoring routine
+	// leaks via leaktest.
+	mux := http.NewServeMux()
+
+	var reqDone bool
+	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+		cn, ok := w.(http.CloseNotifier)
+		if !ok {
+			t.Fatalf("Writer is not CloseNotifier, but %v", reflect.TypeOf(w).Name())
+		}
+		<-cn.CloseNotify()
+		reqDone = true
+	})
+
+	lis, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("Couldn't setup listener: %v", err)
+	}
+	addr := lis.Addr().String()
+
+	srv := &http.Server{
+		Handler: mux,
+	}
+	go srv.Serve(lis)
+
+	cli := &Client{
+		c: &http.Client{},
+		conns: []*conn{
+			&conn{
+				url: "http://" + addr + "/",
+			},
+		},
+	}
+
+	type closer interface {
+		Shutdown(context.Context) error
+	}
+
+	// pre-Go1.8 Server can't Shutdown
+	cl, isServerCloseable := (interface{}(srv)).(closer)
+
+	// Since Go1.7 can't Shutdown() - there will be leak from server
+	// Monitor leaks on Go 1.8+
+	if isServerCloseable {
+		defer leaktest.CheckTimeout(t, time.Second*10)()
+	}
+
+	cli.healthcheck(time.Millisecond*500, true)
+
+	if isServerCloseable {
+		ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+		defer cancel()
+		cl.Shutdown(ctx)
+	}
+
+	<-time.After(time.Second)
+	if !reqDone {
+		t.Fatal("Request wasn't canceled or stopped")
+	}
+}
+
 // -- NewSimpleClient --
 
 func TestSimpleClientDefaults(t *testing.T) {
@@ -400,7 +471,7 @@ func TestClientSniffNode(t *testing.T) {
 	}
 
 	ch := make(chan []*conn)
-	go func() { ch <- client.sniffNode(DefaultURL) }()
+	go func() { ch <- client.sniffNode(context.Background(), DefaultURL) }()
 
 	select {
 	case nodes := <-ch:
@@ -454,6 +525,75 @@ func TestClientSniffOnDefaultURL(t *testing.T) {
 	}
 }
 
+func TestClientSniffTimeoutLeak(t *testing.T) {
+	// This test test checks if sniff requests are canceled
+	// after timeout.
+	// It contains couple of hacks which won't be needed once we
+	// stop supporting Go1.7.
+	// On Go1.7 it uses server side effects to monitor if connection
+	// was closed,
+	// and on Go 1.8+ we're additionally honestly monitoring routine
+	// leaks via leaktest.
+	mux := http.NewServeMux()
+
+	var reqDone bool
+	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+		cn, ok := w.(http.CloseNotifier)
+		if !ok {
+			t.Fatalf("Writer is not CloseNotifier, but %v", reflect.TypeOf(w).Name())
+		}
+		<-cn.CloseNotify()
+		reqDone = true
+	})
+
+	lis, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("Couldn't setup listener: %v", err)
+	}
+	addr := lis.Addr().String()
+
+	srv := &http.Server{
+		Handler: mux,
+	}
+	go srv.Serve(lis)
+
+	cli := &Client{
+		c: &http.Client{},
+		conns: []*conn{
+			&conn{
+				url: "http://" + addr + "/",
+			},
+		},
+		snifferEnabled: true,
+	}
+
+	type closer interface {
+		Shutdown(context.Context) error
+	}
+
+	// pre-Go1.8 Server can't Shutdown
+	cl, isServerCloseable := (interface{}(srv)).(closer)
+
+	// Since Go1.7 can't Shutdown() - there will be leak from server
+	// Monitor leaks on Go 1.8+
+	if isServerCloseable {
+		defer leaktest.CheckTimeout(t, time.Second*10)()
+	}
+
+	cli.sniff(time.Millisecond * 500)
+
+	if isServerCloseable {
+		ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+		defer cancel()
+		cl.Shutdown(ctx)
+	}
+
+	<-time.After(time.Second)
+	if !reqDone {
+		t.Fatal("Request wasn't canceled or stopped")
+	}
+}
+
 func TestClientExtractHostname(t *testing.T) {
 	tests := []struct {
 		Scheme  string