2003 "loose belt" rattle after start

[FireFox31]

Hello, I hear a grinding noise briefly after starting the engine in my 2003 XC70 with 130k miles. When I turn the key and the engine first catches, it gives a healthy rev for 2 seconds before settling at a low idle. But often, the rev is accompanied by a rattling, loose belt noise which starts 1 second after start (during the first rev) and lasts for 2 seconds (after the first rev has idled off).

This has been happening for maybe two years. The dealership couldn't reproduce it and couldn't identify it by description. The car drives fine otherwise and had its 100k mi timing belt change, along with all other services on time.

Any idea how I can isolate, identify and fix this extra rattling sound? Thanks.

[tom_m]

Did you change the idler pulleys and water pump when you did the timing belt change?

[ronkestrel]

It may be noise from the starter, the armature inside the starter motor spins for a while after the engine starts. There's usually a washer at the end of the armature called the brake washer which will stop the armature from freewheeling after the engine is started.
Goodluck... My car has the same noise that you are discribing, it has been doing this off and on for a year.