I got him the cogs then did the staff with enthir and the last quest update was talk to arniel..i talked to him and the quest got moved to completed quests and there's no new dialogue options for arniel. Does that mean it's broken or is there a prerequisite to advance the quest?

Has no one done this quest and can offer help? I know it's probably dead but i'm keepin hope alive

You have to wait a few days.

There's four different "http://www.uesp.net/wiki/Skyrim:Arniel%27s_Endeavor" quests. You've just completed the second. No bugs there; it's completed in your quest log because you finished it.

Go do a few other things, then come back and bug him some more. Then you'll start part three.

thanks for the help but its been a week since i've talked to him and he has no dialogue options so it must be bugged

I had to finish the mage college questline to get Arniel to give me the last of his quests.