The clutch slave cylinder is on the top, front of the transmission, visible from the front of the engine compartment, just to the left of and below the air filter housing as you're facing the engine. On my turbocharged car, it helped to remove some of the intake air hoses. That will be the easy part....


I've used the same Motive Products Power Bleeder on my car ('99 S70 T5M), with good results for the brakes. But I've had tremendous difficulty bleeding the clutch fluid. It seems that, on my car anyway, typical pressure or vacuum bleeding techniques, including the use of the Power Bleeder, or a Mity Vac hand-held vacuum bleeder, or the traditional two-man method, would introduce plenty of air into the clutch hydraulics, rendering the car undrivable. It was only by accident that I found the solution to this problem when I last bled the clutch fluid. The first time I tried clutch fluid bleeding on my S70, it took me EIGHT HOURS before I did SOMETHING that regained pedal pressure, and I wasn't able to identify the solution. This time, I figured it out.

Only by pumping up the pressure in the Power Bleeder to about 20psi, which is about double what Motive Products recommends, was I able to force fluid through the clutch hydraulics without pumping ONLY AIR into the system. Even so, there was still some air in the fluid, but this would self bleed after a few pumps of a partially firm clutch pedal.

At any pressure much less than about 20psi, it seems that a valve somewhere within the fluid reservoir/master cylinder assembly would allow ONLY air into the lines. I've been able to replicate the problem and the solution on my car several times now, so I'm confident that it's not just some one time fix. For what it's worth, I've flushed clutch and brake fluid on perhaps a dozen different models of cars, perhaps as many as fifty times in total, so it's not just a question of inexperience on my part. There's something odd about the design of the S70 clutch hydraulics. So I'll be curious to hear if anyone else has shared my experience with this system, and can replicate the problem and the fix.

BTW, if anyone is of the impression that it's not necessary to flush the clutch fluid, keep in mind that the moisture that most brake fluids absorb will promote corrosion within the master and slave cylinders. On the '99 and later 70-series models (and probably other 99-and-later Volvos, as well), the slave cylinder is an INTEGRATED MODULE with the clutch throwout (release) bearing. When it fails, it will require dropping the tranny to replace. That's big bucks for labor, as opposed to putting it off for a few years by properly replacing your clutch fluid at regular intervals.

Lastly, regarding Vladimir's question about Valvoline synthetic brake fluid, there are two schools of thought about this. On the one hand, synthetic fluid doesn't absorb moisture the way that regular brake fluid does, so it's less likely that high-humidity climates are going to take their toll on hydraulic systems. On the other hand, because synthetic fluid doesn't hold moisture in solution, any water that does get into the system will tend to pool at the lowest point in a hydraulic system -- typically the brake and clutch slave cylinders -- thus PROMOTING corrosion. The solution to that is regular bleeding of the system, although complete flushing might not be necessary as often. That's why synthetic brake fluids tend to be popular for race cars, which tend to get bled between races, but they're still not being used in most OEM applications.

Hope that helps.
--
Jim Rothe, '99 S70 T5M,
http://www.jimrothe.com/volvo/index.html