2000 GMC PASSENGER VEHICLE Engine And Engine Cooling Problems

ENGINE KNOCK IN COLD START(IT SOUNDS LIKE A DIESEL ENGINE TRUCK), THE DEALER SAYS IT'S CARBON BUILD UP,BUT I DID SOME RESEARCH AND FOUND OUT THAT CARBON BUILD UP IS PROBABLY NOT THE CAUSE. THE CUASE IS MORE LIKELY TO BE A PISTON SLAP,BECAUSE WHEN THEY DESIGNED THIS ENGINE THEY MADE THE PISTON SKIRTS TOO SHORT CREATING A GAP BETWEEN THE CYLINDER WALL AND THE PISTON, CAUSING THE PISTON TO RATTLE INSIDE THE CYLINDER WALL WHEN YOU FIRST START THE ENGINE,NOW BECAUSE THE PISTONS ARE MADE OUT OF ALUMINUM THIS MATERIAL EXPANDS WITH HEAT AND CONTRACTS WITH THE COLD,SO WHEN YOU START THE ENGINE YOU CAN HEAR THE KNOCK,BUT AS SOON AS THE ENGINE HEATS UP THE ALUMINUM PISTON EXPANDS AND SEALS THE GAP AND THAT IS WHAT STOPS THE KNOCK. THE DEALER HAS A SERVICE BULLETIN WHERE IT SAYS THAT IT IS A COLD START KNOCK DUE TO CARBON...