This job will take an hour or less if you only replace the thermostat, a bit longer if you flush the cooling system (which I recommend). I like to replace the thermostat every two years. That's way more often than necessary, I imagine, but if your $15 thermostat sticks closed you'll blow the head gasket at best or ruin the engine at worst. Now you're talking in the thousands of dollars range. I like cheap insurance.
Quite a bit of "stuff" needs to be removed to get to the thermostat. Although it's not absolutely essential to remove the throttle body, I feel it's the best way to get to the thermostat. Removing the throttle body only takes a couple of extra minutes, and if you don't do it, the work space is very cramped - sometimes more work is less work in the long run. This is also a good time to closely inspect all the hoses, re-orient hose clamps for the best access and check all clamps for tightness. The genuine Saab thermostat is recommended for replacement, as it's generally said that the aftermarket ones do not operate as well. It's not really necessary to drain the coolant - you'll lose a couple of tablespoons of coolant when you take the throttle body preheat hoses off, and not a lot when you remove the thermostat housing. However, I always combine thermostat replacement with a cooling system flush and coolant replacement, because the only time you can get flush water to flow through the entire cooling system, including the engine block, is to do it when the thermostat is removed. If the thermostat is in place, it will be closed and therefore will block the flow of coolant.
I used to recommend cleaning the throttle body but I now feel it's a waste of time. Carburetors had several tiny passages to allow air bypass for various compensations, so it made lots of sense to try to keep the main bore of the carb clean. Saab's fuel injection system uses a throttle body that has only a single half inch or so diameter bypass that is controlled by the AIC valve. Then there's a big throttle plate. The large bypass path isn't an issue, and you'd have to get an enormous amount of crud buildup to keep the throttle plate from closing properly. Even then the AIC valve would probably be able to compensate. I just don't see any reason to clean the inside of the throttle body.
First, remove all the ancillary stuff. Start with the hoses: The idle air compensator hose (also called the AIC hose - I'm told it stands for Automatic [or Adaptive] Idle Control) and the throttle body preheat inlet and outlet hoses. Picture. Tighten the hose clamps back down on their hoses to prevent them from falling off and getting lost. Disconnect the turbo bypass valve vacuum line from the Y connector (same picture as above). You might also have to cut some cable ties that secure various lines.
Next, remove the electrical connectors from the throttle position sensor and the inlet temperature sensor. Push the bowed side of the wire retainer firmly down against the connector, then wiggle the connector free.
Next is the short rubber intake duct. Work carefully so as not to crack or tear it. Thoroughly loosen the clamps, then flex and rotate the duct to break it loose from the throttle body and intake pipe. Push the intake pipe downward and pry the front of the duct loose, then rotate the duct away from the throttle body. You might have to pry it loose; if so, use a fairly large screwdriver and work carefully. If the hose gets torn or for any other reason leaks at the connections when it is reinstalled, it will make pre-'93 cars run poorly (if at all), because all the intake air must come through the air mass meter. All intake air should also pass by the intake air temperature sensor, and a leak at the throttle body connections would affect that reading.
Now remove the lower AIC hose. It's attached to the bottom of the throttle body, easily viewed from the front after the intake duct has been removed. Picture.
Now the throttle body can be removed. The only problem with removing the throttle body is the front nut. There are two 13 mm nuts on the top, front and rear, and one 13 mm nut on the bottom, in the center. The top front one is readily visible, but there's a brass tube sticking out where the upper AIC hose connects, and that makes it impossible to turn a box-end wrench once you get it on the nut. There also isn't room for a 3/8" ratchet, and a universal joint bends at an unworkable angle. A 13 mm open end can be made to work if the nut isn't too tight, but the angle of attack makes it difficult, if not impossible. A 13 mm socket on a 3/8" drive breaker bar works perfectly. Picture. A 13 mm box end wrench is perfect for the other two. Remove the two top nuts and the bottom one. You'll have to do the bottom one by feel, but it's easy to get to. The throttle body can then be moved out of the way with the throttle cable attached. I recommend against disconnecting the throttle cable, as it's secured by a crimped metal tab. Do NOT try to remove the nut, pulley and spring assembly, as I'm sure the spring would be a nightmare (and maybe dangerous - even small coiled springs store a lot of energy).
Now you can see the AIC variable valve assembly lurking under the intake manifold. It is encased in a rubber mount and the mount just hangs there on a short metal rod. All you have to do is pull the assembly toward the opening and it will slide straight out. Picture. Disconnect the electrical connector from the back end (push the wire retainer bow down, then wiggle the connector off). You might want to tie something to the connector so it doesn't get lost. It looks just like the throttle position connector (although it might be a different color). And here's a picture of the AIC valve after it's been removed.
Remove the two 10 mm bolts that secure the heater hose pipe brace to the thermostat cover (NOTE: these are T30 Torx screws on 94 and later models). There's a ground wire here too (on earlier cars). Picture.
You can now remove the two 12 mm bolts that secure the thermostat cover. You'll have to push the various hoses out of the way. Tap the cover to break it loose, if necessary, then remove the cover. The pipe brace will get in the way if the thermostat stays in the housing, but you can pry the assembly out past the brace.
I quit taking pictures at this point. I had previously changed the thermostat but did not have the camera with me. These pictures were taken later, and I didn't feel like opening the housing needlessly. Everything should be pretty straight forward by this point though. Note that the shorter, cone-shaped end of the thermostat faces out. Note also that the little hole in the thermostat flange is toward the top. Pull the thermostat out. You might have to use pliers, or you might have to pry it out with a screwdriver if the cooling system has been neglected.
At this point, I reinstall the thermostat cover without the thermostat so flush water can circulate freely through the system. The garden hose is then connected to the flush tee (this does not come with the car - you have to install it yourself - see Cooling System Backflush Tee Installation, on the Repair Procedures index page). Now the preheat water hoses are temporarily connected to the throttle body (push-on, no clamps), the reservoir cap is removed and tap water is turned on to force clear water though the system. Note that the preheat hoses are just pushed onto the throttle body connections without clamps, so they can pop loose and vent pressure if you do something stupid, like forget to remove the reservoir cap and apply 50 psi tap water to the closed system. After a few minutes, when the water coming out of the reservoir runs clear, the water is turned off, the garden hose is disconnected and the flush tee cap is reinstalled. Now you have to drain a good bit of water out of the system to make room for the new antifreeze. I do this by disconnecting the wires from the thermoswitch that controls the fan (the positions are carefully marked on the switch first), because I change to a lower-temperature thermoswitch at the beginning of summer and back to a higher-temperature switch at the beginning of winter. You could also remove the lower water hose from the radiator. There's a drain plug on the bottom of the radiator but I don't like to mess with it because it's too easy to wring off (it's plastic, and hollow - designed to fail before the threads in the radiator strip) and because the lower splash panels have to be removed to get to it. Be sure to leave the reservoir cap off so to allow the water to drain freely. After water quits running out, replace whatever you removed to get it to drain.
Installation: Don't you just love it when they say, "Installation is the reverse of removal"? Well, HELL, we KNEW THAT, but we don't always remember the steps. Here they are:
Be advised that you don't want any leaks. After one thermostat replacement I had a tiny leak (never did find it, as the Bar's Leaks eventually plugged it) and coolant dripped down into the clutch assembly and made it chatter. Saab clutches will chatter if moisture gets into the assembly (for a couple of days after the engine has been washed, for instance).
Fit the gasket to the new thermostat, then install it into the cavity. The cone-shaped end faces out and the bleed hole is toward the top. Picture. Install the cover and tighten the bolts snug. You want them tight, but you don't want to wring anything off.
Install the heater hose pipe brace with the 10 mm bolts (T-30 on later models); don't forget to secure the ground wire under one of them (early models only).
Maneuver the AIC valve and hoses into position, connect the electrical plug, and slip the rubber mount onto the mounting rod.
The throttle body is next. Install the throttle body onto the three studs, install the three nuts and tighten them good and snug. Again, the breaker bar and socket work well on the front one, and a box-end wrench works well on the others.
Refit the lower AIC hose to the underside of the throttle body and tighten the clamp. Refit the preheat inlet water hose (lower one, at the front) and tighten the clamp. Refit the preheat outlet water hose (upper one, at the front) and tighten the clamp. Refit the top AIC hose (larger hose at the top) and tighten the clamp.
Reconnect the electrical connectors for the throttle position sensor and the inlet air temp sensor.
Loosely install the hose clamps onto the intake air duct. Install the big end of the intake duct onto the throttle body, then rotate it down and connect it to the intake air pipe. Tighten the clamps.
Reconnect the bypass valve vacuum line to the Y connector. Install cable ties as appropriate (I generally do this suit my own tastes).
Make sure the cap is installed on the flush tee. Check all hose connections for tightness. Make sure the lower hose and thermoswitch are installed and tight. In short, make sure that everything has been reinstalled and reconnected. Add a gallon of antifreeze, a small bottle of Bar's Leaks in the opaque gray plastic bottle (if you believe in Bar's Leaks, as I do) and top up with water to the Max mark on the reservoir. Start the engine and check for leaks. Allow the engine to idle for ten to fifteen minutes - long enough to get the engine up to operating temperature so the thermostat can open. Now check the level in the reservoir again (it will drop when the thermostat opens) and top it up to the Max level. Continue to idle the engine or, preferably, drive the car until it has been running for 30 minutes, to thoroughly distribute the Bar's Leaks throughout the system and allow it to do its work.