Bicycle Mechanics - Unable to quiet a creaking crank

I have a Truvativ Gossamer crank on my primary commuter. I purchased it (whole bike) lightly used and have put 4-5000 miles on it.

A while back, it developed a creak in the crank/bottom bracket area. I disassembled the crank and chainrings, cleaned it and reassembled. The creaking stopped for about four months. Now it's back and I can't seem to quiet it.

I'm fairly certain that it's coming from the left arm. I believe I only hear it on the downstroke of the left arm. I removed it the other night and re-torqued it. The creaking stopped for about a half a block and returned loud as ever.

It's driving me insane. Any ideas? Should I buy new crank bolts? Could it be the bottom bracket (external cups) - should I be looking for frame damage?

http://www.sheldonbrown.com/creaks.html

I have an FSA gossamer crank that does the same thing. i had to remove it, clean it, put loctite on it, retorque it to spec. i expect to have to do it again.

Finally broke down and removed, cleaned, greased, and reinstalled.

Was perfectly quiet for the first day. Climbing up the big hill this morning it started back. I'm so fed-up at this point.

You have my sympathies. There seems to be no obvious reason why a creaking noise accompanying effort expended on the bike should drain one's riding pleasure, but drain it it does. The sense that something might be about to break may have something to do with that.

My crank-area creaking was due to insufficiently tightened chainring bolts, which seems an unlikely cause for yours given that it appears to emanate from the left. But you never know.

The best source on bike noises I discovered in those exasperating days was this: Bicycle Noises, Clicks, Ticks, Repair (http://www.jimlangley.net/wrench/keepitquiet.html)