1996 Toyota Camry serious knocking---

Hi,
When idling, heavy knocking and rattling very, very noticeable and annoying--- the more I drive, more car heated up, the worse it gets-- strange thing is when the car is not idling the car runs perfect no problems what so ever, smooth--

Please help-- tried dry gas, changed timing belt-- can’t find what’s wrong-- can it be time to flush change coolant/antifreeze? I'm at a loss--
Please help
Thanks!
Dave