سلام عليكم اخي محمد

Dear sir 
Thank you for trusting us 
INSUFFICIENT COOLANT in Toyota corolla 2000 and knocking in engine gives that's mean there's aproblem in coolant system and to solve the problem 
1. Check coolant level 
2. Check the temperature thermos
3. Check the water pump 
4. Check the water pump belt 
5. Check the engine hood gas kit 
6.check the engine hood 
7. Check and Clean the radiator 
Best regard
Engineer mohammad