diff --git a/pymongo/monitor.py b/pymongo/monitor.py
index 3d8d167b96..81502591bf 100644
--- a/pymongo/monitor.py
+++ b/pymongo/monitor.py
@@ -177,7 +177,10 @@ def _run(self):
                     # discover that we've been cancelled.
                     self._executor.skip_sleep()
                 return
-            self._topology.on_change(self._server_description)
+
+            # Update the Topology and clear the server pool on error.
+            self._topology.on_change(self._server_description,
+                                     reset_pool=self._server_description.error)
 
             if (self._server_description.is_server_type_known and
                      self._server_description.topology_version):
@@ -185,12 +188,9 @@ def _run(self):
                 # Immediately check for the next streaming response.
                 self._executor.skip_sleep()
 
-            if self._server_description.error:
-                # Reset the server pool only after marking the server Unknown.
-                self._topology.reset_pool(self._server_description.address)
-                if prev_sd.is_server_type_known:
-                    # Immediately retry on network errors.
-                    self._executor.skip_sleep()
+            if self._server_description.error and prev_sd.is_server_type_known:
+                # Immediately retry on network errors.
+                self._executor.skip_sleep()
         except ReferenceError:
             # Topology was garbage-collected.
             self.close()
@@ -377,6 +377,8 @@ def _run(self):
     def _ping(self):
         """Run an "isMaster" command and return the RTT."""
         with self._pool.get_socket({}) as sock_info:
+            if self._executor._stopped:
+                raise Exception('_RttMonitor closed')
             start = _time()
             sock_info.ismaster()
             return _time() - start
diff --git a/pymongo/topology.py b/pymongo/topology.py
index 749299bb74..eb84a344e0 100644
--- a/pymongo/topology.py
+++ b/pymongo/topology.py
@@ -265,7 +265,7 @@ def select_server_by_address(self, address,
                                   server_selection_timeout,
                                   address)
 
-    def _process_change(self, server_description):
+    def _process_change(self, server_description, reset_pool=False):
         """Process a new ServerDescription on an opened topology.
 
         Hold the lock when calling this.
@@ -303,10 +303,16 @@ def _process_change(self, server_description):
                                   SRV_POLLING_TOPOLOGIES):
             self._srv_monitor.close()
 
+        # Clear the pool from a failed heartbeat.
+        if reset_pool:
+            server = self._servers.get(server_description.address)
+            if server:
+                server.pool.reset()
+
         # Wake waiters in select_servers().
         self._condition.notify_all()
 
-    def on_change(self, server_description):
+    def on_change(self, server_description, reset_pool=False):
         """Process a new ServerDescription after an ismaster call completes."""
         # We do no I/O holding the lock.
         with self._lock:
@@ -320,7 +326,7 @@ def on_change(self, server_description):
             # that didn't include this server.
             if (self._opened and
                     self._description.has_server(server_description.address)):
-                self._process_change(server_description)
+                self._process_change(server_description, reset_pool)
 
     def _process_srv_update(self, seedlist):
         """Process a new seedlist on an opened topology.
@@ -414,20 +420,14 @@ def request_check_all(self, wait_time=5):
             self._request_check_all()
             self._condition.wait(wait_time)
 
-    def reset_pool(self, address):
-        with self._lock:
-            server = self._servers.get(address)
-            if server:
-                server.pool.reset()
-
     def handle_getlasterror(self, address, error_msg):
         """Clear our pool for a server, mark it Unknown, and check it soon."""
         error = NotMasterError(error_msg, {'code': 10107, 'errmsg': error_msg})
         with self._lock:
             server = self._servers.get(address)
             if server:
-                self._process_change(ServerDescription(address, error=error))
-                server.pool.reset()
+                self._process_change(
+                    ServerDescription(address, error=error), True)
                 server.request_check()
 
     def update_pool(self, all_credentials):