First off, some stats (from Cook):
No. Appearing: 1
Move: 240' (80')
Att: 1 (fist)
Damage: 3-30 + special
They are described as resembling fire giants, which would put them at approximately 16' tall. 3d10 damage from a fist is bad enough, but the thing is full of liquid fire! This means it's scalding even to touch. A hit does another d10 damage from the heat alone (unless a resist fire or similar is in effect). This also means it's immune to fire-based attacks. (Some like it hot, I guess!)
Oh yes, there's one more thing I neglected to mention about this patina'd powerhouse. If you do manage hurt it with that lovely +3 longsword you're carrying, the wound sprays liquid fire on you! You can make a save to avoid it, otherwise 2d6 damage from what's basically lava spattering your face.
Moving on from the fiery aspects, did you happen to notice that movement rate? I guess being 16' tall gives it a long stride. It has AC 0, which is darned respectable, and TWENTY hit dice! Even a middle range model is sporting close to –if not over– a hundred hit points. It also means it's hitting rather often.
Like all golems, it cannot be hit be non-magical weapons. It is immune to Sleep, Hold, and Charm spells as well as poison gasses, etc. So, if you're facing one of these things, what's the plan?
I recommend panic.
Seriously, though. It only gets one attack per round, and that's melee (not ranged). Keep your distance. Resist Fire would be a handy low level spell for this situation. Ranged attacks, especially spells like Lightning Bolt. A wand of cold would be nice, too. If you have to close, blunt weapons like a cleric's +1 mace will avoid cutting the thing's "skin." Or he might use the spell Striking on a club to let it hit. Although even without the heat/fire damage, the cleric needs to be ready with some healing!
I can imagine this thing guarding a lost temple or a wizard's prize possession. Best of all, it doubles as a furnace, keeping the place warm in winter!