Bleeding the clutch

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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.

What I use to bleed the clutch:

	I found a cap that wasn't a perfect fit for my master cylinder, but that I could get to seal. I don't remember where the cap came from. The best bet would be to buy a stock cap for the master cylinder (Saab PN 89 66 152), or get one from a junk yard.
	Once you have a cap that can be made to seal, you can buy a tire valve stem at an auto parts store and drill a hole in the cap to accept the valve stem (I believe it takes a 1/2" hole). Install the valve stem in the cap by pulling it through from the bottom side until it snaps into place.
	Get a manual foot-operated tire pump with a built-in pressure gauge. You might be able to use a low-volume electric pump, but I worry about over-pressurizing the system. Thirty to 40 psi works fine. You can put a foot-operated pump on top of the fender/battery and pump it by hand (put a piece of plywood or something on top of the battery to keep from shorting out the battery cables/posts).
	Fill the fluid reservoir to the top with fresh DOT4 brake fluid. Do not use fluid that has been open for more than a few hours, and throw any unused fluid away afterward - opened fluid will absorb moisture, even if it's tightly capped. Moisture will corrode the hydraulic cylinder walls and ruin a hydraulic system.
	Put a piece of clear plastic tubing onto the slave cylinder bleed nipple (remove the plastic cap on the top of the trans to get to the bleed nipple). Home Depot has clear plastic tubing that works well.

Install the cap on the master cylinder - tighten with Vice Grips if necessary, to get a good seal, but grasp the reservoir to avoid overstressing it.
Now you can attach the tire pump, pump up a few pounds of pressure (20 to 40 psi) and then loosen the slave cylinder bleed nipple . You should see fluid and air bubbles come out through the plastic tubing.
Tighten/close the bleed valve.
Remove the cap from the reservoir and refill it to the brim with fresh fluid. Reinstall the cap tightly.
Push the clutch pedal down by hand until you meet some slight resistance (or to the bottom of its travel if no resistance). Pull it back up to the top of its stroke. Repeat until the resistance point doesn't occur higher on the stroke - 4 or 5 strokes minimum

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.

There are several alternative methods of applying pressure or suction to the system:

An ideal one is to rig a larger container with a pressure line input fitting in its cap, and a fluid out line that goes through the cap, and to the bottom of the container. Again, you will need a modified reservoir cap with a fluid input line fitting. Now you can fill the big container with lots of fluid, attach the lid, attach the pump to the pressure fitting, and a plastic hose from the container's fluid-out fitting to the reservoir cap's fluid-in line. Now you can pressurize the container, open the bleed valve and pump a steady stream of fluid from the container into the reservoir and through the system. With such a system, you don't have to worry about topping up the reservoir. Systems are available commercially to do just this, but they probably will cost close to $100, and the cap may not fit your reservoir.

Another idea that's known to work (THANKS to Peter Charak):

Get a bicycle or motorcycle inner tube (the very skinny ones typically used for 10-speed bikes are a bit too small).

Cut it about a foot from the valve.

Now you have a section on one side of the valve about a foot long and a section on the other side of the valve that's five or six feet long. Tie a knot in the end of the one-foot section.

Unscrew and lift out the reservoir cap/warning switch assembly, and set it aside.

Carefully stretch the end of the long section of inner tube over the mouth of the reservoir. Slide a suitable clamp over the inner tube and tighten it to clamp the tube onto the reservoir.

The tube's valve stem can now hang over the fender about mid-wheel height, and can now have a bicycle pump or other source of air pressure attached to it.

A clear plastic line from the bleed nipple may be led up and snagged in the coil of one of the hood pop-up springs and then down into a container to catch the expelled fluid.

Now you can pump pressure into the inner tube, crack the bleed valve and bleed fluid out of the system.

The one thing I don't like about this system is that it's a bit cumbersome to remove and reattach the bicycle tube each time to refill the reservoir.

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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