You can use
First assign A view to TitleView
UILabel *titiLbl = [[[UILabel alloc]initWithFrame:CGRectMake(0, 0, 100, 44)]autorelease];
titiLbl.text = @"Title Name";
self.navigationItem.titleView = titiLbl;
Then to find the height of titleView
CGRect navigationframe = self.navigationItem.titleView.frame;
NSLog(@"navigationframe Height=%f",navigationframe.size.height);
and please keep this in mind that if any view is not assigned to titleView of the NavigationItem It will return you 0.000;