I just did Mzinchaleft and there was no Grimsever where it's supposed to be. This has happened before as well and http://www.uesp.net/wiki/Skyrim:Grimsever, it seems as if it won't spawn if the PC is below Level 14, which my char is. I wonder if it will spawn there after Level 14 even if having done the dungeon? If so, I can just go back. If not, I'm a bit miffed.

I believe it is placed there by having the conversation with Mjoll. If so, then doing that (after level 14, as that's a condition on the dialogue) will spawn the sword, and you can go back for it. It shouldn't respawn the enemies, and you may be able to go in the back door.

No, I've gotten it several times w/o first talking with Mjoll (UESP says so as well). I'll try going back after hitting Lvl 14 and see how it goes. Annoying that you are punished for doing it at an earlier level - if anything it should be the opposite.

EDIT: Wrong link above and messed up if I try to edit. http://www.uesp.net/wiki/Skyrim:Grimsever%27s_Return.

Well, knowing how they design these things, I'd expect if they made it available at a lower level, it would be a leveled list, so you'd get a steel sword or an elven one before level 14.

Mzinchaleft does respawn enemies - even the big steam dude at the end. I like going back there and clearing it again. Grimsever, of course, does not respawn.

I'm pretty confident that if you cleared it below level 14 and Grimsever didn't spawn, that it will spawn when you go back at a higher level. I'm not positive though since I don't go in there intitially until Mjoll asks.

I should have written that just the going back shouldn't make them respawn. There is one dungeon where you can clear it, get a quest to go back, and it's refilled the same day, as the quest itself resets the dungeon. Can't remember which that was, but it wasn't Mzinchaleft.

Man who cried Wolf does, in fact, respawn the dungeon Wolfskull Cave.

You need to be above level 14 and Mjoll can't be reserved by another quest, which usually means that you've visited Riften once and seen the scene between her and Aerin.