Flushing/Bleeding the Saab 9000 Braking System

Introduction

The Saab 9000 braking system, like most others, is a hydraulic system requiring bleeding after any part of the system has been dismantled and also flushing with new fluid at specified intervals (I do it when I buy a car and every two years thereafter). Most recently, I performed this procedure after replacing all the brake hoses on my '96 Aero with stainless steel braided hoses.

My main reference while writing this article was the Haynes 9000 workshop manual.

A note about brake fluid standards:
The recommended brake fluid for the Saab 9000 is DOT 4 (or compatible). When I replaced the brake hoses on my 9000 Aero, I flushed the system with DOT 5.1 brake fluid and received a number of comments from US 9000 owners expressing concern that this would be incompatible with the braking system (to be fair, I did describe the fluid as "DOT 5"). DOT 5 brake fluid is a silicone-based fluid and is not compatible with DOT 4. It is also less suitable than DOT 4 for ABS systems, because of its higher compressibility. I believe that the DOT 5 standard is not recognised in many European countries, hence the widespread use of the term "DOT 5" as shorthand to describe fluid that actually conforms to DOT 5.1.

DOT 5.1 brake fluid is a low-viscosity, high-temperature fluid compatible with DOT 4 and DOT 3. Its low viscosity makes it ideally suited for ABS systems, where it helps the system modulate the braking pressure more easily. Its higher wet and dry boiling points should make it more resistant to brake fade under heavy use. I have had no problems with the braking system since installing this fluid.

DOT 5 and DOT 5.1 are very different standards, confusingly named by the US Department Of Transport. Of the two, only DOT 5.1 is compatible with DOT 4. Do not use DOT 5 fluid unless you have a good reason and know how to purge the system of all DOT 4 fluid beforehand (this usually requires complete dismantling of the braking system and cleaning of the individual components with a suitable solvent). Mixing DOT 5 fluid with any traces of DOT 4 will form precipitants that will clog the braking system.

If in doubt, use DOT 4 brake fluid. It will be fine for the driving conditions encountered by most 9000s.

Time required

Unless you come across some seized bleed screws (I haven't yet on a 9000), the procedure should take around 10-15 minutes per caliper.

As usual, double this for the first caliper if you haven't done it before.

Tools required

I assume some basic tools, such as a jack, axle stands, socket set, etc. However I do not assume you will already have all the necessary metric socket and spanner sizes, especially if you are in the USA. Here is a list so you can make sure you have all the necessary sizes before you start.

• 2 litres (4 US pints) of DOT 4 or compatible brake fluid
• 9mm ring spanner or brake line spanner (open-ended will do if the bleed screws aren't too tight)
• Piece of plastic or rubber tubing to fit the bleed screws, at least 25mm long
• Glass jar

Procedure

Flushing the system is almost the same as bleeding all four calipers, except that you bleed off more fluid. On a car with manual transmission, DON'T press the clutch pedal while the fluid in the reservoir is low. The clutch shares the same reservoir and fluid and doing this may introduce air into the clutch. After flushing the braking system, the clutch should really be flushed as well to prevent contamination of the new brake fluid. I haven't done this without a pressure bleeder, so I won't describe it here.

The bleed screws are 9mm on my '96 (ABS with ATE calipers all round). I'm told the Girling front calipers (non-ABS and early ABS non-turbo) also have 9mm bleed screws.

FLUSHING THE BRAKING SYSTEM

1. To give yourself a head start, it might be quicker to draw off some of the fluid from the reservoir with a turkey baster.
   
   
2. Bleed one of the calipers until the reservoir is almost empty (see below). On ABS systems, this should be one of the front calipers.
   
   
3. Top up the reservoir to the MAX mark with new fluid.
   
   
4. Continue bleeding that caliper until new fluid appears, topping up the reservoir if it reaches the MIN mark. The new fluid will be considerably lighter in colour than the old fluid.
   
   
5. Top up the reservoir to the MAX level.
   
   
6. Repeat steps 4 and 5 for each of the other calipers. On ABS systems, be sure to bleed the front calipers first.
   
   
7. Test the brakes while stationary before driving the car.

BLEEDING THE FRONT BRAKES (AND REAR BRAKES ON NON-ABS SYSTEMS)

Note that on non-ABS systems, the calipers may be bled in any order. On ABS systems, the front brakes must be bled first. The manual procedure is described here, which requires an assistant. I use a pressure bleeder, which makes life a lot easier.

1. Jack up the car at the corner at which the caliper is to be bled and support it with an axle stand.
   
   
2. Remove the roadwheel.
   
   
3. Top up the brake fluid reservoir to the MAX mark.
   
   
4. Remove the dust cap from the bleed screw.
   
   
5. Put some new brake fluid in a clean glass jar.
   
   
6. Fit a ring spanner over the bleed screw, then fit one end a plastic or rubber tube onto the bleed screw and immerse the other end in the fluid in the jar.
   
   
7. Ask your assistant to press the brake pedal fully several times to pressurise the system, then to hold it down.
   
   
8. Open the bleed screw about 1 turn and allow fluid to flow into the jar, maintaining pressure on the pedal. Tell your assistant not to release it under any circumstances until you tell them to, even if the pedal hits the floor.
   
   
9. When fluid stops flowing, close the bleed screw and ask your assistant to release the pedal slowly.
   
   
10. Check the reservoir and top up if necessary.
    
    
11. Repeat steps 7-10 until no air bubbles appear in the fluid. If flushing the system, continue until new, clean fluid appears.
    
    
12. Remove the tube and spanner and refit the dust cap.
    
    
13. Refit the roadwheel.
    
    
14. Lower the car.
    
    
15. Top up the reservoir to MAX.
    
    
16. Repeat as necessary for the other calipers.
    
    
17. Test the brakes while stationary before driving the car.
    

BLEEDING THE REAR BRAKES ON ABS SYSTEMS

N.B. I found that my pressure bleeder (which is fed from a spare tyre and is rated to 20 PSI) could not bleed the rear brakes on my '96 ABS braking system. I'm told that more pressure would have done the trick. I simply followed the manual procedure below instead.

1. Jack up the car at the corner at which the caliper is to be bled and support it with an axle stand.
   
   
2. Remove the roadwheel.
   
   
3. Top up the brake fluid reservoir to MAX with new fluid (keep it above MIN throughout).
   
   
4. Remove the dust cap from the bleed screw.
   
   
5. Put some new brake fluid in a clean glass jar.
   
   
6. Fit a ring spanner over the bleed screw, then fit one end a plastic or rubber tube onto the bleed screw and immerse the other end in the fluid in the jar.
   
   
7. Have your assistant switch the ignition on (so the ignition, oil, etc. lights come on), but not actually start the engine, and to press on the brake pedal and keep it pressed.
   
   
8. Slacken the bleed screw by about one turn and allow brake fluid (and air) to flow into the jar. If it takes a while, close the screw again and check the level - top up if necessary.
   
   
9. When only fluid (no bubbles) is seen in the tube, close the bleed screw (remembering to stop and check the level periodically). If flushing the system, continue until new, clean fluid appears.
   
   
10. Refit the dust cap.
    
    
11. Refit the roadwheel.
    
    
12. Lower the car.
    
    
13. Top up the reservoir to MAX.
    
    
14. Repeat for the other rear wheel if necessary.
    
    
15. Test the brakes while stationary before driving the car.