Replacing the thermostat on your Saab is an easy way to make sure the cooling system is functioning properly at all times. A Saab thermostat allows coolant to enter the engine when it reaches a set operating temperature, which keeps the engine from overheating and ultimately allows warm air to enter the heating system. You can tell when your Saab thermostat is beginning to fail by checking the temperature gauge. All Saab temperature gauges stay centered between low and high when at normal operating temperatures; if the temperature stays too low or to high, you may have a sticking thermostat.
Drain the cooling system. As replacing the thermostat will result in loss of coolant, it is best to complete a full drain and refill of the cooling system when the thermostat is changed. Loosen the coolant reservoir cap to release pressure. Next, loosen the drain plug on the radiator. Use a drain pan to collect the dripping coolant.
Remove upper radiator hose. Pinch the clamp that holds the hose in place and pull the house off of the housing where it connects to the engine. The housing from which the radiator hose is removed is the thermostat housing.
Unbolt thermostat housing. The thermostat housing must be unbolted from the engine. Saab thermostat housings are held in place with four bolts; once they are removed, the housing should pull off easily.
Replace thermostat. Remove the thermostat from its housing and replace it with a new one. It is easiest to put the new thermostat right in its spot on the engine block and not to tighten it down the housing and thermostat together.
Tighten thermostat housing. Place the thermostat housing over the thermostat and tighten it using the four bolts that were removed. Avoid over-tightening the bolts, as this could make it difficult to remove the housing when the thermostat is next changed.
Replace upper radiator hose. As long as the clamp removed in Step 2 is still in good shape, it can be reused.
Fill cooling system. With the thermostat and radiator hose back in place, the cooling system can be refilled with coolant. All Saabs before 2001 use Saab Coolant, while models from 2002 on use GM's Dexcool coolant, available at most service centers and parts stores. Be sure to mix the coolant with distilled water in a 50/50 mix.
