Coolant Change and Thermostat Install in the SAAB 9-5

You might as well change out the thermostat when you flush the coolant on the SAAB 9-5. Both are easy jobs. It’s a little messy, but satisfying when you are finished.

Symptoms of a thermostat stuck in the open position includes a lack of heat inside the car and the temperature gauge on the instrument panel never reaching up to the 9 o’clock position. Symptoms of a thermostat stuck in the closed position includes the temperature gauge reading extremely hot and possibly a repair bill for thousands of dollars sitting in your seat when you pick the car up from the dealership after it stops running due to overheating.

I encourage you to pay the few extra dollars for a thermostat that is build to lock in the open position when it fails.


I purchased the MotoRad fail-safe thermostat from my local Autozone, the price was $6.

You will need a pair of pliers, a pan to catch the coolant, two gallons of undiluted coolant, at least four gallons of distilled water, a running garden hose (if you are the adventurous type and your tap water isn’t too terribly hard otherwise buy some extra distilled water and skip the garden hose part), 13mm and 10mm sockets with matching extender and a socket wrench.

The system holds -7.4 liters- of coolant/water total. You will want a mix of between 50/50 and 75/25 coolant to water when you are finished. You won’t have to over think it, the car is built to make this mixing automatic, the reservoir and radiator will drain half of the liquid while the other half stays in the system. I’ll explain this part in detail when the step comes.

Start by losing the protective plastic panel from under the front bumper, like you would for an oil change. Slowly unscrew the lid from the coolant reservoir. Let any pressure release before completely removing the cap.

On the driver’s left side of the engine bay, near the headlight, at the bottom of the radiator is the the green plastic petcock used to release the coolant. Place the catch pan under this green petcock to catch the coolant.

Reach down from above and turn the green petcock counter-clockwise a quarter turn and then pull it out to release the coolant. Pliers can be gently used if it won’t turn by hand. The part is made of plastic, so care should be taken not to tear it apart. You can push the petcock back in at any time to stop the flow of coolant.

Let all the coolant drain out while you move on to the thermostat part of the project.

The thermostat is on the back corner of the engine. There is a large coolant hose that goes from the radiator to the thermostat housing.

The hose can be seen in the bottom right corner of this image.

Follow the hose to the thermostat housing and use pliers to release the clamp and pull the hose free. Some coolant will spill out.


The thermostat housing is attached by two 10mm and two 13mm bolts. Remove all four of them. The 10mm bolts hold a ground wire and a bracket, the 13mm bolts clamp the house to the engine. The space is tight so use an extender and take your time.

After the four bolts are removed, pull the house off and take out the old thermostat.


The rubber washer that comes with the thermostat has a valley on the inside so it can be placed around the metal disk as shown.

Stick the new thermostat back into place, taking care to point the little hole in the disk towards the top. The disk may also be labeled to show which direction is the top.

Bolt the housing and ground wire back on and securely reattach the hose. The coolant will be drained by this point.

Temporary close the petcock and fill the system up with water. The correct method is to use only distilled water in the system, but I used the garden hose to flush the system because I like to tempt fate. Use your own judgment, tap water can plug up your system with minerals.

Wear gloves while working with the hot engine and coolant to prevent burning yourself.

Once the system is filled with some water, and with the reservoir still open, start the car, turn on the heater inside the car, and give it a few moments to warm up so everything starts flowing. Now is the time to check for leaks on your thermostat job.

Once warm, open the petcock to start releasing fluid while adding fresh water to the reservoir to keep the system full. Do this until the liquid from the petcock runs clear. (if you are like me and are using a garden hose, switch to adding your four gallons of distilled water.) Close the petcock, shut the car off, and allow everything to cool down. You now have water in your entire coolant system. Let the car stand until cold.

Here is the secret to mixing 50/50 coolant. The car, when cold, holds onto half of fluid and release half of fluid. Open the petcock one more time and it will release half of the water in the system. Close the petcock and lock it with a quarter clockwise turn. Add your undiluted coolant until the reservoir reads full and you now have a 50/50 mixture in your system. Isn’t that neat.

The water and coolant will mix quickly as the engine runs. Once the coolant is given time to mix and any air is released, top off the reservoir with more undiluted coolant.

A day later you will want to check the coolant with a “coolant tester”. These can be the simple eyedropper like devices that use specific gravity to check the coolant mixture or strips of paper treated with chemicals that offer more detailed results. My eyedropper type tester was $1 from Walmart.

29 thoughts on “Coolant Change and Thermostat Install in the SAAB 9-5

  1. Thank you for posting this informative and useful instruction on flushing a radiator and replacing the thermostat. I completed the process in a reasonable amount of time. I did have difficulty with opening the petcock to drain the radiator. And, if I ever do this again I would likely pull the lower radiator hose.

    The petcock is in a difficult location to apply leverage with much of anything. I did find; however, that a 13/16 box end wrench will fit up from the bottom and just fit over the flanges of the petcock handle providing enough leverage to open it without damage.

    Thanks Again

  2. I need help locating the end of the transmission breather hose. One end came loose and I don’t seem to find where this end needs to be connected. Your help will be greatly appreciated. I own a 2002 Saab 9 5 Aero wagon.

    • If the other end is still connected to the transmission, then you are all set. The one end just hangs loose, usually near the fuse box under the hood. I remember I panicked when I found the hose was loose the first time. It really looks like it should go to something, but it doesn’t. :O)

  3. Thanks. It was leaking oil from there that is why I panicked. I will move it to place where it stands higher to prevent more leakage.

  4. Is the Transmission breather tube the one that runs next to the positive battery feed to the rear of the fuse box on top of the ABS module in the 2000 9-5? About 1/2″ OD and 1/4″ ID, comes off the trans at the left of the battery and near where the trans dipstick tube comes up from below the engine compartment? Top end does not have any sign that it has been clamped or pushed over any connector.

    • That description sounds exactly like the breather tube. It just hangs loose near the fuse box. It looks like it should attach to something, but it doesn’t. I don’t know why they don’t label it or something. It’s upsetting when people come across it for the first time… I know I freaked out when I found it years ago.

  5. Thanks for your post–I am in the middle of trying to flush my system. But why does the owner’s manual state that the coolant capacity is in the 7 liter range, but you say that the system holds almost 4 gallons total?

    • I have no clue why I put 4 gallons in the post. It must have been a long day. I’ve changed it to the correct 7.4 liters (1.85 gallons). Thanks for catching that and good luck on your system flush!

  6. Thanks for the guide! It took me just over an hour to do, your guide helped me loads. Taking the petcock out took 20 minutes alone! I used a socket that someone mentioned above to get it off. Also I attached a hose pipe to the bottom of the petcock drain (then fed it straight into a nearby drain) so I didn’t need a bowl to drain into. Also, I didn’t need to remove the tray under the car, my tray had a hole in it to attach the hose to the bottom of the drain plug! Anyway, thanks for the guide!

  7. It’s been mentioned several times that there is a small hole in the disc that goes in first to the engine that allows for the release of air. However, the thermostat I purchased has no such hole. Is that going to create problems for me down the road. The rand I bought is Superstat by Stant and is supposed to be top of the line. Should I return it and buy one with the hole?

    • You’re in good shape. The hole isn’t found on all thermostats. It’s important that a thermostat with the whole be lined up at the top because the hole is there to help move any air bubbles in the system up to the reserve tank.

  8. Could you just do a basic drain and fill w/out starting the car? And when you are done filling w/new coolant would leaving the resovoir cap off when car is running to release air bubbles be adviseable? Isn’t that basically the same thing as turning the heat on?

  9. I am following your well documented instruction. But I am stuck. I removed all 4 bolts. But unable to pull the house. It is really tight. I don’t want to break anything on the way while giving so much pressure. Do I need to move the bracket of 10 mm bolt before I pull?

    I also noticed when I pulled the rubber hose from the junction the joints has more residue. I am wondering whether same residue built up in the junction which is not giving way to come out?

    I really don’t want to take it to shop as I already there.

    Thanks in advance.

    • There shouldn’t be anything else holding the housing in place except the grime collected over time. Try putting the handle end of a screwdriver against the edge of the housing and tapping the other end with a rubber mallet. That should knock the thing loose without causing damage. Good luck! Reinstalling everything should go much smoother.

  10. Thanks for the reply. My other question is do I need to move the bracket before removing the hose as I don’t see any room for removing the hose junction due to bracket.

    How to move the bracket?


    • I don’t remember having to remove any brackets, but I’d say to not be afraid to loosen or remove anything you think will make the job easier (as long as you feel comfortable being able to reattach everything when you’re done). I pulled the hose while the car was still warm. The hose was flexibility enough to come off and then I removed the thermostat housing after that. I do remember difficulty getting the hose back on, especially with the stock clamp. The second time I had to replace the thermostat I used a screw type hose clamp instead.

  11. Sorry for making it unclear. Hose came out perfect. The problem is with thermostat housing which is stuck even after removing the 4 bolts. Trying my best… Thanks for the input.. I do have the screw type hose clamp.

    • What model year is your 9-5? I wonder if something changed in the design because mine came off once the bolts were removed. If you can get a digital camera positioned at the right angle and you set it on micro, try taking photos of the area from directions you can’t otherwise see and maybe you’ll find what is binding it up.

  12. After getting a onsite mechanic to help me out. I found I removed the 13 mm bolt not belonging to the top housing but near to that area there is another 13mm bolt. Anyway all is fixed and running great with correct heat and right heat gauge.

    Another issue which I faced today is car stopped when I try to restart from a parking lot. Checked the error code to be p1312, p1334. It cranks but makes big humming noise near dash board. Checked all the fuse, all looks good.

    Car is towed to the shop. After doing some research it is possible not tightening the earth properly to the thermostat housing!! So before mechanic keep his hand on the car I will try to check that and change the DIC (spare). I hope it fixes the issues. If not I am broke.

    Any thoughts?

  13. Yep, that sounds like the direct ignition cassette. I don’t know how things are now, but replacement DICs were hard to find and expensive a few months ago.

  14. hi there,

    will attempt this on the week end, my radiator blew for the 2nd time in 6 week this time the bottom tank of a new radiator, has to be the thermostat, do you agree??

    anyhow one more thing i have though to ad is 4 litre’s of petrol because if it blows again… well you get the picture.

    john brisbane australia

  15. Funny, but that is scary it keeps going out.
    The thermostat is a good start. You can test the old thermostat after you remove it by placing it in a cup of boiling water. If nothing happens, you’ve found your problem. If the thermostat opens while in the water, you might have to do some more searching for a cause.

    What year and engine is your 9-5?

  16. I have a 2002 95, V6. Can you tell me where to locate the thermostat? I can’t find it according to the directions provided here.

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