Moss customer Gus Harris told us about his method for bleeding the hydraulic system for the clutch in a NA/NB Miata, and we thought he explained it so well, that we should share it with you. To thank him, we’ve sent Gus a Moss Gift Certificate. If you have a fun story or an educational how-to, please contact us by filling out the form here!
The Easy One Person Clutch Slave/Master Cylinder Bleeding Method
I recently purchased the second Miata (2000, my first a 1990) I’ve owned and it soon needed the dreaded clutch slave cylinder/master cylinder replaced. I wasn’t sure which was the problem so I just replaced both and I’d recommend that to anyone rather than replacing one and then having to go back and maybe replace the other later. My only reservation on doing this repair myself was the bleeding. But, after watching a youtube video I found a great and easy way to effectively bleed the system after installation of the slave cylinder, master cylinder or both. In fact, it was simple. So, here is my description of how to do this one person bleeding that is fast, simple and effective.
First, bench bleed whatever cylinders (slave and or master cylinder) you intend to install. There are a number of ways to do this and these methods can be found easily in an online search for how to do the bench bleeding for both the master and slave cylinders. So I won’t explain that part here. Main objective is to get some of the air out and some fluid in both parts prior to installation since it will make the final bleeding much easier.
The next part is the most effective way I’ve found to bleeding the system once the parts are installed. It only takes a few minutes and works like a charm. You will need the following…a small “oiler pump” like you can buy at most auto parts stores for oiling things. One with either a thumb pump trigger or a squeeze type trigger is fine. While they have fairly small reservoirs they will be sufficiently large enough to hold enough brake fluid to fill your system with fluid to spare. And you’ll need some clear tubing and of course a new bottle of brake fluid. (*Note: brake fluid is corrosive to paint. Keep water and rags nearby, water neutralizes brake fluid. -Moss)
Once the parts are bench bled and installed fill the pump oiler with new brake fluid. Attach a piece of the clear tubing to the oiler…long enough to go from the engine compartment down to the bleed screw on the slave cylinder (about two feet). Pump the oiler until the fluid is solid in the plastic tubing and coming out the other end. Then temporarily pinch off or plug the end to keep it full of fluid and without any air coming back into the tubing…or minimal air from coming back in. Then, fill the master cylinder reservoir about halfway to the full mark with new fluid and leave the top cap off. Now drop the tubing down through the engine bay so it is at the bleeder valve on the slave cylinder and prop the oiler can up somewhere in the engine compartment. Then get down where the slave cylinder is from the wheel well and unplug the end of the plastic tubing and get it on the bleeder valve securely. Make sure to loosen the bleeder valve enough so fluid can easily go through it. Now you are ready to start the bleeding process. Get up from the wheel well and lean into the engine compartment and take the oiler can that is now connected to the slave cylinder with the tubing.
You are now going to pump fluid down into the slave cylinder and up through the line into the master cylinder…with any air escaping up through the fluid in the master cylinder reservoir. This works easily because air wants to rise up from the system…not down as most people usually try to pump it. It’s just the reverse using this method and the air will come out far more easily. You just lean over the fender into the engine compartment and pump the oiler…watching the fluid as it goes down into the slave cylinder and also being able to look over at the master cylinder reservoir for air escaping as fluid and air bubbles come up into the reservoir.
While it may seem like the small oiler doesn’t pump a lot of fluid it will if you just keep pumping it. You will eventually begin to see air bubbles come up through the reservoir (make sure cap is off of reservoir) and escape the system. The level of fluid in the reservoir will begin to rise as you are pumping especially as air escapes the system. Once fluid rises above the full mark stop pumping and remove fluid from the master cylinder reservoir (suction or whatever method to get it out) but leave enough fluid in the reservoir (again about halfway to the full mark) to keep air from getting back in the system. Also make sure you still have plenty of fluid in the oiler can…or add some if it’s low. Continue the pumping procedure. You may need to do this about 2 or 3 times until you no longer see any air bubbles rise up through the fluid in the reservoir and only the level of fluid rising. On the final pumping go ahead and pump enough fluid up into the reservoir that it aligns with the max mark. Now, close off the bleed screw at the slave cylinder making sure it is tightened sufficiently. Get into the car and you should have a nice firm clutch pedal! It really does work like a charm. Remove the tubing from the bleeder valve, lift the oiler pump with the tubing from the engine bay without dripping fluid on fender or engine parts…and you’re done! This whole process should only take you about 30 minutes. It is the most effective bleeding procedure I’ve ever used and it only takes one person to do it…with no other assistance!
*Note: on 1990-2005 Miatas, consider upgrading to the Extended Length Braided Stainless Steel Clutch Line by Techna-Fit.