Jquery dialog open delay in Javascript method

<div id="dialog1" title="Waiting" style="text-align:center;background-color:#ffffff;border:none;display:none;">
       <img src="~/Images/icon-load.gif" border="0" align="left" hspace="12" height="175" width="175" />
   </div>

function addnewentity() {


    var aa= document.getElementById('aaa').value;
    var bb= document.getElementById('bbb').value;
    var cc= document.getElementById('ccc').value;
    var validation = document.getElementById("valmsgentity");

    if (aa!= "" && bb!= "" && cc!= "") {

        validation.style.display = "none";
        $('#dialog1').dialog('open');
        $("#dialog1").prev(".ui-dialog-titlebar").hide();

        var source = {
            "A": aa, "B":bb , "C": cc
        }

        var jsonsource = JSON.stringify(source);
        var method = "POST";
        var request = new XMLHttpRequest();
        request.onload = function () {
            var status = request.status;
            var data = request.responseText;
        }
        request.open(method, createurl, false);
        request.setRequestHeader("Content-Type", "application/json;charset=UTF-8");
        request.send(jsonsource);

        setTimeout(function () {
            $('#dialog1').dialog('close');

            ScrollToTop();

            $("#message").show();

            //200 OK ; 201 Created ; 202 Accepted
            if (request.status == 200 || request.status == 201 || request.status == 202) {

                $("#message").text('Added successfully!!!');
                $("#message").css("color", "green");
                setTimeout(function () { fadeLabelOut(); }, 5000);
                setTimeout(function () { location.reload(); }, 7000);
            }
            else {

                $("#message").text("Failed to add !!!");
                $("#message").css("color", "red");
                setTimeout(function () { fadeLabelOut(); }, 5000);
                console.log(request.responseText);
            }
        }, 2500);
    }
    else {
        validation.style.display = "block";
    }

}