Clutch Master Cylinder Repair and Bleeding

by Lowell Felix Tortona

I thought I have all the necessary tools on hand when I started the process. But I guess, I wasn't that prepared as I thought I was. This forced me to go back and forth to a nearby hardware shop in my vicinity to buy such tools. To help the DIY guys out there who are planning to repair their clutch master cylinder and bleed their clutch, here are the tools you must have.

1. Master Cylinder Repair Kit
   Fujiura Ltd. (FIC) [Made in Japan] or any 323/MX-5 compatible repair kit.
   Serial Number: FR-3106 (for 323/MX-5)
2. Rachet
3. Socket/Rachet extension
   
4. 12 mm. hexagon socket with at least 1 inch of depth
   
5. 10 mm. open wrench
   
6. 8 mm. close wrench
   
7. Circlip plier
   
8. About 500ml of DOT3/DOT4 brake fluid
   
9. Jack
   
10. Screwdriver
    
11. Wheel wrench
    
12. WD-40
    
13. A partner for bleeding the system
    
14. Absorbent rags
    
15. Clean newspaper/paper towels (to be used on the rebuild process of master cylinder)
    
16. Cotton buds.
    
17. Bottle/ Plastic container to dispose brake fluids
    
18. Syringe (not necessary)
    
19. 4-in by 4-in Glad-o-wrap plastic seal (you can get it in your kitchen)
    
20. Water
    
21. Uninterrupted time
    
22. Snacks (yum... yum...)

Let me first describe the location of both the master and slave cylinder. For the master cylinder, it is located inside your engine hood. Remember the two cylindrical reservoir connected on the car's firewall in front of the steering column? Well, the master cylinder unit is the one with the smaller cylindrical reservoir. For the slave cylinder, it is located under the front-passenger part of our miata. It can be clearly seen after the right-front wheel is removed. It is like a door actuator thingy with rubber boot cover (similar to the shock absorber rubber boot cover) on it.

Now let me explain how to proceed with the process.

A. Removing the Master Cylinder

1. Remove the reservoir cap of the fluid container on the master cylinder.
   
2. Using the syringe, remove some brake fluid from the container until it reached the minimum level. Dispose the fluid in a bottle/plastic container.
   
3. Put the 4-in by 4-in Glad-o-wrap plastic seal on top of the master cylinder fluid container. Seal tightly. (This prevent spilling of fluids when the clutch pipe line is removed from the master cylinder.
   
4. Put the reservoir cap and close tight on the master cylinder fluid container.
   
5. Put an absorbent rag under the master cylinder body.
   
6. Locate the clutch pipe line that is connected on the master cylinder body. (long pipe with about 1 mm of diameter)
   
7. Using a 10 mm open wrench, loosen the screw connection (by unscrewing it counter-clockwise).
   
8. After the screw is completely removed, pull the clutch pipe lining out of the master cylinder.
   
9. Locate the 2 screws connecting the master cylinder onto the car's firewall.
   
10. Spray some WD-40 on them to ease up the removal of the nut. (Believe me... I really had a hard time removing those things.)
    
11. Using a 12 mm. hexagon socket connected to a socket extension and a rachet, remove the nuts (by unscrewing it counter-clockwise).
    
12. After removing the 2 nuts, you can now remove whole clutch master cylinder. (Be careful of fluid spillage....)

B. Rebuilding/Repairing the Master Cylinder

1. Remove the thin woven lining that is lying in between the master cylinder and the car's firewall. (To prevent from fluid spillage later on our rebuild process.)
   
2. Work on a clean paper or paper towel.
   
3. Look at the end of the master cylinder (the one that is connected to the engine firewall) and locate the circular clip that integrates the whole master cylinder. (a horseshoe like circular object with two holes on its end)
   
4. Press the piston using a screwdriver and remove the circular clip with the use of the circlip plier.
   
5. After removing the circular clip, the piston inside the master cylinder will eventually be removed. (You can then notice that only a cheap plastic were used as a component.)
   
6. Shake the master cylinder until the remaining 3 components (spring, cap, circular plastic lining) are out.
   
7. Make sure that the repair kit contains the the following components (piston, spring, cap).
   
8. Clean the whole internal master cylinder body using fresh brake fluid and wiping it with cotton bud. (Do not use water or other solvents in cleaning this one.)
   
9. After cleaning it, pour on some fresh brake fluid in it.
   
10. Soak the new spring, cap, circular plastic lining, piston with fresh fluids.
    
11. Put the cap on solid (flat) end of the spring and re-insert it into the master cylinder body.
    
12. Next, attach the circular plastic lining and afterwards set the piston into the master cylinder. Remember that the flat side will be used to contact with the circular plastic lining and the side for the push rod should be exposed.
    
13. Reinsert the circular clip by pushing the piston with a screwdriver and clipping the circular clip (like putting the clip on a Koni shock absorber in a reverse manner).
    
14. Now, you have rebuilt your clutch master cylinder.

C. Re-installalation of the Master Cylinder

1. Put back the thin woven lining that was removed in B-1.
   
2. Set the master cylinder back onto the engine firewall.
   
3. Using the 12 mm socket, socket extension and rachet, screw back and tighten the two nuts that secure the master cylinder onto the car's firewall.
   
4. Reconnect the clutch pipe lining.
   
5. Using the 10 mm open wrench, screw and tighten the connector screw between the master cylinder and the clutch pipe lining.
   
6. Pour in fresh brake fluid into the reservoir.
   
7. Now, the master cylinder have been successfully re-installed.

D. Bleeding of Clutch

1. Jack-up the right front side of the car.
   
2. Remove the wheel.
   
3. Sit down beside the right front side wheel-well of the car (face towards where the shock absorber is located)
   
4. Locate the slave cylinder (You can then see it on the left side part of shock absorber... which is directly connected to the clutch body.)
   
5. An air bleed valve can be seen connected to the slave cylinder. Put the 8 mm close wrench on it and make sure that the air bleed valve is tightly closed. (Screw clockwise.)
   
6. Put some rags near the trajectory path of the air bleed valve.
   
7. Ask a friend to sit on the driver's seat.
   
8. Make sure that the clutch fluid reservoir is full. Fill if necessary.
   
9. Let him slowly push (by counting 3-5 seconds) the clutch pedal until it bottoms out.
   
10. Let him maintain the clutch pedal on the floor until you give a signal to release it slowly.
    
11. Now slowly loosen (screw counter-clockwise) the air bleed valve until a squirt of bubbly fluid emerge.
    
12. Re-tighten the air bleed valve.
    
13. Give a signal to your friend to release the clutch pedal slowly.
    
14. Repeat process D-8 to D-13 (around 5 to 7 times) until you notice that the squirt that is coming from the air bleed valve is clear brake fluid and the clutch pedal feels tight.
    
15. Make sure to tighten the air bleed valve.
    
16. Fill the clutch fluid reservoir to the maximum level.
    
17. Close the cap of the clutch fluid reservoir.
    
18. Clean with water all the parts where the brake fluid spilled onto.
    
19. Using the wheel wrench, re-install the wheel and tighten the nuts in an X pattern.
    
20. Jack-down the right front side of the car.
    
21. Completely tighten the wheels.
    
22. Afterwhich, you can test drive and see if everything is OK.

Finally, you can now clean-up, eat your snacks with your friend and enjoy the rest of the day top-down driving your Miata.

I hope this would serve as a reference for you guys out there who plans to fix your cars in case such problem occurs.

Frank Reedy comments:

I recently replaced the clutch on our 1990 Miata.It has 146,000+ miles on it and decided to do the hydraulics also. I had done brakes before on many cars so this was not new to me. I noticed the article on rebuilding the clutch master cylinder and noticed there was no mention of honing the bore of the unit. This should be done because the walls do rust. An easy fix is use at least 400 3M wet sandpaper rolled around a round file. Use a little fluid and it will clean the bore to a new shine which will let the plunger do a better job. I clean the cylinder with aerosol brake cleaner that evaporates quickly. Apply dot 3 fluid to all surfaces, reassemble and your clutch will feel like new.