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Volvo 850 problem

Has anyone else experienced this? I have a manual trans. "94 850, 157K,no problems until recently. When the car gets hot and idles too much in traffic, or drive-thrus, it makes this hum, click, click, click, hum, click, click, click sound, sometimes for an hour after it is turned off. New battery and alternator. I have a mechanic I trust, but he is a one-man operation, and I need the car and can’t leave it with him for days. Help!

Where is the sound coming from? Under the hood? Under the dashboard? Under the car? We need more information.

Yes, the hood, as far as I can tell.

The “click click” may be a relay in the relay box. Take the lid off the relay box, and put your finger on the relays. If the clicking is occuring, you should feel a relay vibrate. If you do, tell your mechanic, or switch that relay with another relay.
Hmmmm, the hum may be caused by a component operated by the relay, or whatever is causing the relay to click.

I neglected to mention that the car is a bear to start after the hum, click marathons.( The battery has been replaced twice in the last two months, which we attributed to the old alternator.) All the activity with the engine turned off - is it draining the battery? Could the starter be the problem?