Hi, replaced my clutch master cylinder and am trying to power bleed the clutch system as per the manual. But wasn't sure the most effective way, i mean should I pressurize the whole reservoir, or just the line coming off the reservoir to the clutch master cylinder. Any one tackle this one lately?
Yes, pressurize the reservoir. It is fairly simple to make your own pressurization system. (Spare reservoir cap with a pressure fitting placed in the center and some regulated compressed air) Use about 15 psi to pressurize the system and you should have no problems. It is a tight squeeze to reach the bleed valve on the clutch m.c., but I found it easiest to reach from underneath the car.
i've been struggling with bleeing the clutch for over one year (the air bubbles always seem to come back), and even tried using a motive power bleeder to no avail. i've finally figured out how to do it easily.
the following is from another forum;
How to bleed the hydraulic circuit for your clutch --
This weekend I changed the brake fluid on my 86 5000S. It was, I think, a bit
of unbridled enthusiasm with the right front brake that led to drawing the
reservoir down below the hose level for the clutch circuit.
You know you are in trouble when the clutch pedal lays forlornly on the
firewall Anyway, both Bentley and the impotent Haynes state that the
clutch circuit cannot be bled by ordinary means, and I can tell you from
personal experience that they are right. A vacuum pump applied to the bleed
screw (a mighty-vac) also does not do the trick, presumably because too much
air leaks in between the slave cylinder and the bleed screw threads. Both
books recommend pressure bleeding, but a mechanic told me a much better way.
You can bleed the **** thing in less than 5 minutes, and all you need are the
wrench, about a meter of hose, and a jar!
Fit the hose over the bleed screw (it must be snug) and run it into the jar.
Place the jar on the cowl (on top of the huge "Audi" logo). It must be higher
than the reservoir. Pour a little fluid into the jar and make sure there is
plenty in the reservoir. Crack open the bleed screw, and slowly (with your
hand), pump the clutch pedal through its full range of motion. You are done
when the hose is full of fluid and no more bubbles come out. Close the bleed
screw, test the pedal, and clean up. It worked like a champ for me.
WHY THE @#*! ISN"T THIS SIMPLE TECHNIQUE IN THE BOOK?
1. instead of using a jar, i simply re-routed the hose back into the hydraulic fluid reservoir so that it completed a full circle.
2. when hand-pumping the clutch pedal, you can feel if you're pumping hydraulic fluid as there is some resistance. if you feel no resistance, you're pumping air. if you're pumping air, you'll have to slow down your pumping and make sure there's enough brake fluid in the reservoir so it's not allowing air to enter back into the system.