Recheck the timing belt installation and confirm the camshaft and crankshaft marks are aligned. Being even one tooth off can put the valves and pistons out of sync and cause knocking that was not present before the belt was replaced.
The owner of a 1989 Dodge Caravan with 190,000 miles reports engine-area knocking that began after the timing belt was replaced; there was no noise before. The expert suggests the camshaft and crankshaft may have been moved out of time relative to each other, and that even one tooth off can keep the valves and pistons from moving together as they should.
