MG Car Repair: 67 sprite clutch bleeding, austin healey sprite, phillips screwdriver

Question
Hi Barrie
I have a 67 Austin Healey Sprite with a new master clutch slave and slave cylinder. We have tryed bleeding the clutch by gravity, pressure bleeding, back bleeding and vaccume, all with no result.The clutch line was previously replaced and routed up and around the top of the fire wall and we rerouted it to infront of the heater box thinking that this might help but still do not have any built up pressure in the pedal.Do you have any suggestions, guesses, or experiences?

Answer
Hi Konrad.  I think it was a mistake to re-route the pipe over the firewall.  There must be no loops where a large bubble of air can collect.  If possible the pipe should be a continuous rise from the slave cylinder to the master cylinder.  Sometimes there is a big upward loop as the line enters the master cylinder, and this can be reduced by careful bending of the pipe.

I often find that you can force the bubbles out of the line as follows:

1) Remove the filler cap from the master cylinder and make sure it is almost full.  Top it up if necessary.

2) Disconnect the slave cylinder from the engine, pull it off the operating rod and allow the cylinder to dangle vertically downwards.  This is difficult on an early Sprite with a solid line, easier on the later ones with a flexible hose.  

3) Holding the slave cylinder with one hand, use a large Phillips screwdriver and push it quickly upwards into the slave cylinder with the other hand, so that all the fluid is forced upwards into the clutch line.  Bubbles of air should now appear inside the master cylinder.  

4) Lower the screwdriver and allow the slave cylinder to refill itself.  

5) Repeat the operation until no more bubbles of air appear inside the slave cylinder.  You can usually hear them when you are pumping the screwdriver.

That usually solves the problem.