A healthy clutch is necessary for the operation of any manual transmission automobile. A soft or spongy clutch may make it difficult to change gears without causing damage. The most common cause of a soft clutch is air in the system, which can be removed by bleeding the system. In most systems, this can be done much in the same way as bleeding brakes; however this can damage the master cylinder of a Mazda Miata. Instead, using this gravity bleed system to bleed the clutch fluid will alleviate the problem without damaging your Miata.
Open your hood and locate the clutch slave cylinder. It is usually toward the front of the car, near the bumper.
Place a container underneath the slave cylinder.
Open the bleeder valve by unscrewing it slightly. The bleeder valve should be under the slave cylinder and distinguishable because of the rubber cap on its end. You will have to remove this cap when opening the valve.
Let the fluid drip out until it eventually pours out in a steady stream. Keep an eye on the clutch fluid level; do not let it dip below the minimum line. If it is gets low use new fluid to top it off.
Close the bleeder valve as soon as the fluid begins to pour out continuously and replace the rubber cap.
Slowly pump the clutch a few times. If after a few pumps the clutch feels normal, then you are finished. If the clutch still feels too soft, you will have to repeat the process.
Top off the clutch fluid in the reservoir.
Be patient, it may take a long time for the fluid to start dripping from the bleeder valve.
If the clutch fluid gets too low, it can seriously damage the master or slave cylinder; be sure to keep an eye on it.