2001 Pontiac Bonneville rod knocking

My car was running perfectly, used no oil, but with the high mileage, (437000), I took some advice and had my mechanic replace the timing chain, gears, water pump, and oil pump. 2 days later, (less than 100 miles), I lost oil pressure, power, and when it quit on the South Padre Island bridge, coolant was running out from places unknown. I had it towed to my mechanic, ($200.00), and he tells me a rod is knocking, that he pressurre tested it and it is all simply coincidence as regards the timing of the breakdown. Says he can find no coolant leak. I say bullshit. What did he screw up? I suspect improper installation of the oil pump. I'm baffelled that he can find no coolant leak.