I'm currently at the end of exploring a Dwemer ruin and have encountered a steam breathing Centurion that absolutely kick my butt. I'm a leve 24 battlemage using destruction, restoration, and one handed axe. My armor is around 260. The room is pretty tight so it's difficult to kite him too far.
Any advice will be appreciated.

Grab two shock staves and magic the hell out of him. You can stay a good distance away from him and deal constant damage.

Circle strafe. You can bait the Centurion to fire his steam prematurely. Once he begins the animation he is locked in place. Punish.

First, don't let its steam breath hit you. Second, my brother and I find it useful to constantly be circling it while attacking. I'm not sure how effective it is at evading its ranged attack, but it seems to work wonders close up.

It's a bit naughty, but see if you can lure him through a low doorway or something else he will get stuck in, and attack from afar. That's what I advised my brother to do. Personally I've never had a problem with them.

I tend to play keep away, hit and run or merry-go-round something. At least long enough to heal. Don't forget your shout's! Being Etheral is very handy.... when your health gets low shout... run away.. heal... ready a ranged attack.

I attack them with magic then use Ethereal shout while recovering to a safe distance and then attacking again.

There is often oil on the floor... kite them to it and set it on fire.

Ah, i remember my first centurion fight. So epic! I used hit-and-run tactics, but it was still bloody hard.

Use hit and run tactics or distance.

Hit him with a big weapon at the back, then run away when he turns. Keep behind him.

Or run off and use magic or archery and keep running off to a safe distance when he catches up.
And avoid their steam attack.

A master centurian was hard. He chased me all over the place, as I hit him with magic in the time it took for him to catch up, which was'nt long.

beat it with a hammer no technology survives such punishment!

Try to stay behind Centurions, they have difficulty turning around. Getting behind them can be difficult, but once you're there you are good to go.

When there a enemy that I can't handle I usually use the shout slow time and use my strongest hits then hide then keep doing en till he dies but some times if you have a companion they will fight it for you so you can hit it in the back that a couple things I do.

Skyrim is all about exploiting the incompetent AI more than anything else. Find something you can hide behind etc, jump on to pleaces where they cant reach you etc. Lets say you cant beat a troll on your own, just make sure to jump onto a stone and he cant reach you.

Also there is the dragonshout, unrelenting force which will knock him on his ass while you light him/her/it up with fire.

*furiously taking notes*

Kill Them.

You can usually see these guys a mile away, before they become activated. I usually pump a couple arrows into it (only 1 gets the x3 sneak bonus but that's better than none!) and then I Fire breath it. My mage is by no means overpowered but I was able to drop a centurian master before it got into striking distance of me. Don't forget to grab the centurian dynamo core, by the way. Cool to look at, and could come in handy in future.

edit: oh, yeah, and don't use frost weaponry on it.

open console, click him, type kill, enter, DONE lol

But seriously, magic or a very strong melee weapon while blocking is what i normally do.

Centurions are much more dangerous from afar than when in close combat. My 2-step strategy (I use a warrior character, no magic involved)

1. To get close: from a safe position (behind a wall etc) trick him to perform his steam attack. Wait until it ends and then sprint until reaching him (safer option: use whirlwind sprint to get close. Safest option: use become ehtereal to get close)

2. Once you can go melee on him he will try to punch you. His punches deal lots of damage but are super slow. If you circle around him you can avoid being punch and then hit him while he pulls back his massive arm. Rinse and repeat.

Small question I myself have: does anybody know if a ward would block the centurion's steam attack?? Never tried and I'm curious.

Ice spike ice spike ice spike

it may be weak in power bu its really over powered because it seems to stop any attacks all the enemy will be able to do is stare at you dumbly (and angrily) at least til lyou run out of magicka then go use a potion or 40

I'm a one handed shield guy which seems to work pretty well with the Centurions as long as I can keep them staggered with blocks.

Thanks a lot for everyone's advice. I'm happy to report that the Centurion is now a pile of Dwemer scrap. I did a combination of straifing around his legs and trying to get behind him while hitting him with my axe and periodically running off and hitting him with fireballs & firebolts. I also tried Ice Spikes, but found the he actually resisted them, but not my fire spells.
BTW wards work a little against his steam attack, but not very well, so they're not worth using.

Usually I can run away from them and leave the cell before they can catch up. Or, I find a doorway to get them stuck in, or I circle and attack when I can.

I do not stand toe to toe with them.

James Purefoy said it best in a movie called "Ironclad":

"Hit them.... hard!"