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The clutch hydraulic system must be bled after any clutch repairs, or any time that the clutch hydraulic system has been disconnected at any point. The purpose is to flush all air out of the system and ensure that the clutch hydraulic system is completely filled with hydraulic fluid. Saab specifies DOT 4 fluid, so use only that - not DOT3, not DOT 5, although my understanding is that fluid that is labeled for BOTH DOT4 AND DOT5 is OK.
Overview: The system consists of a fluid reservoir (behind the battery), a line from there to the clutch master cylinder (above and behind the clutch pedal, inside the car), a line from the master cylinder to the slave cylinder (in the clutch/transmission area), and a bleed nipple (accessible from the top of the transmission). The object is to either pressurize the reservoir and then loosen (open) the bleed nipple, or to loosen the bleed nipple and then apply suction/vacuum to the bleed nipple - in either case, the object is to move fluid through the system and expel any air that has been introduced due to the system having been opened. Note that the fluid level in the reservoir must be kept high enough to avoid the intake of any air when the bleed operation is in progress. In general, the bleed nipple is loosened/opened only when pressure/suction is applied and the fluid level is high, and tightened/closed to allow adding new fluid.
I have found that there are three keys to bleeding the Saab clutch:
1) The clutch must be either pressure bled or vacuum bled; if you try to use the pump-hold-bleed method, the pedal will stay on the floor.
2) The reservoir must be filled to the brim and you must refill it to the brim after each bleed cycle.
3) If you hand-pump the pedal through its free travel after each bleed cycle, the bleed will be greatly expedited.
Expanding point 1: That's just the way it is. Saab clutches just aren't like your average car. You can foot-pump the clutch on most cars and the pedal will return on its own; on the Saab, if you push the un-bled pedal to the floor, it just stays there, and pressure never builds.
Expanding point 2: If you remove the feed line from the clutch master cylinder and allow the fluid to flow out of the reservoir, the flow will stop when the fluid level drops about 1/2" below the top of the reservoir (maybe an inch on earlier models). The clutch feed line tap-off point on the earlier cars (pre-93 or 94) is about half way up the reservoir, while the connection for the later models is at the bottom of the reservoir. That gives the impression that all or most of the fluid in the reservoir is available for the clutch, but it just isn't so! For the clutch feed line connection, there has to be some sort of internal stack or tube that comes up nearly to the top of the reservoir, because I'm telling you, once the fluid gets much below the top, it just won't flow. Is that important to know? You bet it is! If the fluid drops below that point while you're bleeding, you'll just pump fresh new air into the system! So it is absolutely imperative that you keep the reservoir full. I have found that if I try to bleed more than once without topping up on the later model system, I get below the fluid level and introduce massive quantities of air. In effect, you're just wasting your time and brake fluid if you don't refill after each bleed cycle.
Expanding point 3: This is a tip from Tom Townsend at Townsend Imports, and it works wonders. After you pressurize (or vacuum) the system and expel fluid and air, close the bleed valve. Now push the pedal down by hand until you encounter some resistance (close to the bottom of the stroke), then pull the pedal back up. Repeat, pushing down to resistance, then pulling back up. Magically, you should notice that the resistance occurs higher with each stroke. If bleeding only minor amounts of air out of the system, this one trick might finish the bleed after one cycle. If filling both the master and slave cylinders and all the lines, it might take two or three cycles to get noticeable results from this trick, but I am convinced that this is one of the secrets to successfully bleeding the Saab clutch.
Slave cylinder bleed nipple pictures.
Repeat steps 1 through 6 until the pedal feels normal and actuates the clutch. If you keep the reservoir properly full, this should only take a couple to a few cycles, depending on the amount of air in the system. When done, reinstall the plastic cover over the bleed nipple.
Commercial systems also exist that allow attachment of a vacuum pump to the bleed nipple to suck fluid through the system. I've never used one of these, but they are said to work quite well. The main consideration, again, is to make sure that the reservoir stays full enough to avoid the intake of air.
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