This could be for few different reasons. But since you are noticing that noise after the replacement of the timing belt and oil pump. It is a good chance something did not get installed properly or one of the component might have failed.
It could be that the oil pump does not provide enough pressure at low engine speed so the engine is noisy.
Best course of action would be to test the oil pressure and make sure it is at the correct level. Also inspection the timing belt and verify that it is lined up properly.
You check the oil pressure by using a oil pressure gauge. Typically you can get those gauges from your local auto parts store to use.
This engine should have a minimum of 30 kPa (4.35 psi) of oil pressure.
I have included the oil pump and the timing belt procedures for your reference.
Please let me know of any questions.
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Friday, September 24th, 2021 AT 10:29 AM