Session cookies do not change using ajax and nodejs server

I want to change a session cookie after an asynchronous request but no matter what I tried I keep failing. My request is as follows:

$.ajax({
    type: "POST",
    url: "/setStatus",
    data: { userId : _userId, token: _token, tokenSecret : _tokenSecret, service : service, loggedIn : _loggedIn, authorized : _authorized },
    xhrFields: { withCredentials: true },
    crossDomain: true
}).done(function(reply) { alert('finished'); });

Setting the session variables on the server.

exports.setStatus = function(req, res)
{
    req.session.userId = req.body.userId;
    req.session.token = req.body.token;
    req.session.tokenSecret = req.body.tokenSecret;
    req.session.service = req.body.service;
    req.session.loggedIn = req.body.loggedIn;
    req.session.authorized = req.body.authorized;

    res.header('Access-Control-Allow-Credentials', 'true');
    res.writeHead(200);
};

The setting on the server are as follows:

app.use(express.favicon());
app.use(express.logger('dev'));
app.use(express.cookieParser());
app.use(express.bodyParser());
app.use(express.session({ secret: 'keyboard cat', store: new RedisStore({ host: 'localhost', port: 3000, client: dbcon })}));
app.use(express.methodOverride());
app.use(passport.initialize());
app.use(passport.session());
app.use(express.static(path.join(__dirname, 'public')));
app.use(app.router);

I forgot to mention that on simple requests the session cookies change as expected. Any ideas?