When replacing the engine coolant Thermostat (LY7) start by partially draining the cooling system. Don't divide the upper-level and lower intake manifolds. Take off the upper and lower intakes. Remove the thrustrod nut, the thrust rod guide bolt , and the upper ball stud then its nut and locking plate. Then, remove the Thermostat housing coolant inlet pipe and throw the pipe o-ring seal away. You need to remove the Thermostat bolts then pull the Thermostat and throw away the Thermostat seal. In the case of installation, mount the Thermostat with new Thermostat seal, and check bolts of the Thermostat to 10 n.m (89 lb in). Replace the coolant pipe with new seal and fasteners (1 and 3). Resecure the surge tank hose back to the Thermostat and reinstall the upper Intake Manifold to the lower Intake Manifold. Finally, fill the cooling system.