Hummer 12710303 Pump Assembly, Oil

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Remove the timing chain cover and oil pan. Remove the oil pump pick-up tube mounting nuts and bolts and lower the pick-up tube and screen assembly from the vehicle. Remove the oil pump retaining bolts and slide the pump off the end of the crankshaft. Remove the oil pump cover and withdraw the rotors from the pump body. Clean the components with solvent, dry them thoroughly, and inspect for any obvious damage. Also, check the bolt holes for damaged threads and the splined surfaces on the crank-shaft sprocket for any apparent damage. If any of the components are scored, scratched, or worn, replace the entire oil pump assembly. There are no serviceable parts currently available. Prime the pump by pouring clean engine oil into the pick-up tube hole, while turning the pump by hand. Position the oil pump over the end of the crankshaft and align the teeth on the crankshaft sprocket with the teeth on the oil pump drive gear. Making sure the pump is fully seated against the block. Install the oil pump mounting bolts and tighten them to the proper torque specifications. Install a new O-ring on the oil pump pick-up tube, then fasten it to the oil pump and the engine block main studs. Install and align the timing chain cover, then install the oil pan. The remainder of installation is the reverse of removal. Add oil and coolant as necessary. Run the engine and check for oil and coolant leaks. Also, check the oil pressure.

Remove the oil pan. While supporting the oil pump, remove the pump-to-rear main bearing cap bolt. Lower the pump and remove it along with the pump driveshaft. If a new oil pump is installed, make sure the pump driveshaft is mated with the shaft inside the pump and a new driveshaft retainer is used. Position the pump over the dowel pins on the rear main cap and make sure the slot in the upper end of the driveshaft is aligned with the tang on the lower end of the oil pump driveshaft. The oil pump driveshaft drives the oil pump, so it is absolutely essential that the components mate properly. Also, note that no gasket is used between the oil pump and the rear main cap. Install the mounting bolt and tighten it to the torque specifications. Install the oil pan and refill the engine with fresh oil. The remainder of assembly is the reverse of the disassembly procedures.

Install the mounting bolt and tighten it to the torque specifications.

Remove the pump-to-rear main bearing cap bolt.