2004 CHEVROLET EXPRESS 2500 Engine And Engine Cooling Problems

AS I ATTEMPTED TO SPEED UP IN TRAFFIC, I HEARD A NOISE AND THE VEHICLE SUDDENLY SLOWED DOWN. I WAS ABLE TO GET IT OFF THE HIGHWAY ON TO A SIDE ROAD. ONCE THERE, IT WOULD NOT START. ON CLOSER INSPECTION, I SAW THAT THE BELT HAD COME APART AND OFF THE PULLEY'S. I HAD THE VAN TOWED TO MY HOME AND SUBSEQUENTLY, FIXED/REPLACED THE BELT. SINCE THAT TIME, I BEGAN TO HEAR A LOW KNOCKING, MORE SO WHEN I TURNED ON THE AIR CONDITIONING. WHEN IT BECAME LOUDER ON ALL GEARS AND WHILE PARKED, I TOOK IT TO HOLLER DRIVERS MART, IN WINTER PARK, FL. ON 01/19/2012, I WAS TOLD THAT THE FLYWHEEL HAD SHEARED AROUND THE AREA WHERE IT WAS BOLTED ONTO THE TRANSMISSION AND CONNECTED TO THE ENGINE. IT ALSO HAD FRACTURES IN AND AROUND THE SAME AREA OF THE SHEARING. TECH INFORMED ME THAT I HAD...

MYSTERIOUS COOLANT LEAK. RESERVOIR IS LOW AND NEEDS REFILLING OFTEN. MECHANIC HAS PERFORMED PRESSURE TEST TO NO AVAIL. NO COOLANT ON GROUND AT ANY POINT. NO VISIBLE SIGNS OF LEAK. THIS BEGAN RIGHT AFTER 2ND CRACKED FLYWHEEL WAS REPLACED. AT THE SAME TIME A LIFTER KNOCK BEGAN AS WELL. 1ST FLYWHEEL WAS REPLACED AT 103K (3K OUTSIDE OF EXTENDED WARRANTY). 2ND FLYWHEEL REPLACED AT 143K. VAN IS KEPT IN MINT CONDITION, OIL CHANGED EVERY 3K W/O FAIL. VEHICLE SEEMS TO BE IN OTHERWISE TERRIFIC CONDITION. 1ST AND ONLY OWNER. DATE REFERRED TO IS DATE OF 2ND FLYWHEEL CRACK. *TR