Technical Article - Bleeding the Clutch the Other Way

Workshop techniques require special equipment; handymen use funnels and tubes. My techniques simply call for an indifference to barked knuckles and contortions.

Method 1: "The Contortionist" - for 404s

Open the bonnet, remove the round plastic clip-on top of the clutch-fluid reservoir. You should be faced with a small cup shaped cast iron reservoir integral with the master cylinder. Check the fluid level is between 1/3 and 2/3 full. Ensure you have two clean fingers, one to scratch your nose the other to poke the small spring valve sitting up in the middle of the reservoir under the fluid. Now open the driver's door, stand inside it with your right foot on the ground as near to the hinge as possible. Place your left foot gently on the clutch.

Reach around under the bonnet and push down the valve in the reservoir. Dibble with your left foot on the clutch. If you cop a jet of fluid in the eye you were pushing not dibbling and don't say I didn't warn you! When dibbling stops producing bubbles and gives a smooth ripple on the surface of the fluid allow the valve to seat and give some full clutch strokes, push-hold-release-pause. Open the valve again and go back to dibbling, repeat the whole sequence until you get no more bubbles.

Method 2: "The Rough Nut" - For 504s and Later

Open the bonnet, take the top off the combined brake/clutch reservoir and check that it is near the full mark. It might help to have an assistant keep an eye on this reservoir. Now take a big screwdriver or lever and climb under the passenger's footwell. Find a way to jamb your lever in the bell-housing to operate the clutch-yoke directly.

If you have a spring-loaded type slave (most are) then the piston should follow the actuating rod out as you move it. Pause and release. It would be encouraging if the observer called "I can see bubbles!" at this point. It doesn't take many cycles to do the job.  Note that 504 clutches bleed themselves in normal use. A soft clutch means that you ran out of fluid (leaking brakes?), or you have clutch problems and need to fix the hydraulics anyway.  If you are re-assembling then just before you slip the slave back into its collar and secure it with the big circlip: hold the inlet hose up and give it three or four pumps using a rod. That's all it takes and the system is bled.

Theory

All of the cylinders, master or slave should be oriented so the inlet is near the top. They are big enough for air and fluid to sort themselves out: so that whatever came in, any air present will be the first thing out on the return stroke. The volume of the tube is small by comparison as long as the system is not to pressurised! On 504s we help this natural purging by compressing the diaphragm spring manually so the slave can move at low pressure. On 404s we help by releasing the non-return valve that prevents air returning to the reservoir.

Happy Pugging,

Michael James