[R-P]

I drive an auto. That should inspire confidence...

But I've been battling a problem with a Hyundai clutch. It is a fairly simple system: it is a pull type clutch, so there is a part that pulls really hard against the springs of the pressure plate. Once you apply enough pressure (actually pulling force), the clutch is disengaged (or engaged? semantics) so the turning flywheel is no longer in contact with the gearbox.

These springs from the pressure plate cause the pedal to return to the upright position via the hydraulic pressure. Unless I open the bleedingscrew on the secondary cylinder, then the pedal stays down.

So if the Volvo system is similar to this, I would check 3 parts:

First the fluid level: the Hyundai has a combined brake and clutch brake-fluid container. The inlet of the clutch is much higher up (so the clutch stops working long before the brake does when you start loosing fluid). But what we found is that it starts sucking in air when the fluid level is 1cm ABOVE the inlet. I would have to cut it open to figure out why, but I think it has to do with the maze-like structure inside the container (to prevent slushing around???).

Second is the bleeder screw. Is it tightened correctly? Or any leaks (fluid) anywhere in the system?

Third is the main cylinder: Once we had it out and free of fluid, I could feel it putting pressure on the output, not on the fluid input. This was when I pushed IN the cylinder. When I pulled it out, it would suck in air through the inlet. There is a valve in the inlet that closes when the cylinder builds up pressure and opens (to let in fresh fluid) when it releases pressure. Keeping both inlet and outlet sealed off with your fingers, you can check if that valve works correctly. It could still leak a little, but I think you would likely notice a big leak.

Hope this helps. I'm a noob in clutches, but I hope my new found understanding, however little, may be of use to you.