UK Car Repair: 1979 midget, hydraulic clutch, moss motors

Question
Greetings,  In reference to the hydraulic clutch of my 1979 midget. After a long layup I put my midget back on the road. As expected, I had some seal problems including the clutch cylinders leaking. I rebuilt master and slave with moss motors seals. I refilled system with dot3 and all appeared fine for period of time. Now, when the car is cold, the clutch catches about 2 inches of the floor, and as it heats up the pedal gets spongy and gets closer to the floor.  It eventually gets to the point where I can`t get it into 1st with out shutting the car off and restarting, and then it creeps. I have bled this a number of times, and am getting no air out of the system.  When the car cools of, I am back to the 2 inches. I have heard that special fluids are to be used. Can you help me.  Thank you, and have a great day!   Ken

Answer
I only use dot 4 fluid which was what was called for, as far as I know only US cars used dot 3. It can be hard to bleed out the slave cylinder, is the bleed nipple on top?  Have a friend hold the operating rod with a large lever to prevent it pushing in as you bleed it.