Belts can squeak. Get a tube of belt dressing and dab some on the belts - it will spread itself around. I don't like the spray dressings because only a little gets on the belt.
If the belts are still 1996, they should be changed.
The timing chain is permanent, internal, oil-lubricated and does not squeak.
Flushing the radiator will have no effect on the noise.