(1a) You may need to loosen the boost line hose clamp to get access to the drain valve. While wiggling the pliers to break the valve corrosion loose, turn the valve CCW and unscrew/pull it out. A 3' piece of 1/4" tubing can be attached to the valve outlet to save the anti-freeze.

Tools : 11mm wrench, pliers

(2) When enough anti-freeze has drained, close the valve and replace the boost hose clamp.

Tighten the clamp to 95 in-lb [11 N•m]

(3) Remove radiator hose clamp and hose from thermostat housing. Slide hose from outlet fitting.

Tools: Clamp Pliers

(4) Remove the three water outlet-to-eylinder head bolts and remove the water outlet connector (Fig. 73).

Tools: 10 mm wrench

(5) Clean the mating surfaces of the water outlet connector and clean the thermostat seat groove at the top of the thermostat housing.

NOTE: Do not let any debris fall into the thermostat cavity when cleaning the gasket surfaces

Tools: Scraper or knife

NOTE: Make sure the thermostat seal is installed on the outer lip (bottom) of the thermostat flange. (See parts diagram below)

3. Tighten the capscrews to 18 ft-lb [24 N•m]

Tools: 10 mm wrench

4. Replace the radiator hose and clamp.

5. Refill radiator with the appropriate water/anti-freeze mix. Use low-silicate antifreeze that meets ASTM4985 (GM6038M specification) criteria.

Coolant flow through cylinder head.

Coolant flow to heater core.