Start of the show, Naruto is tricked into stealing the ninja scroll, that dude who tricked him is about to attack and take it from him, Iruka steps in without hesitation not caring about what happens to him. Their bond seems pretty strong to me.
Maybe you feel like they don't have a lot of moments, but it's just a thing with Naruto that a lot of side characters don't get a lot of screen time, some more examples being Rock Lee, Neji.
And its good that you mentioned that you're still in between Shippuden, i was about to point something out that would be a spoiler, when you get towards the end of the show you'll see it and understand their connection more