6 Steps to Bleed Clutch Fluid on a Mazda MX-5 using a Gunson Eezibleed Kit

Why the pedal goes soft on an NB and NC MX-5

Air enters the clutch circuit two ways on the Mazda MX-5: through a slave cylinder that has weeped past its seal, or during a fluid change where the reservoir ran dry. On the NB (1998 to 2005) the slave is external, bolted to the bellhousing with a bleed nipple you can reach from above. On the NC (2005 to 2015) the slave is concentric, wrapped around the input shaft inside the bellhousing, so the only access is the bleed screw on the line union near the gearbox. Both share a master cylinder mounted on the pedal box, fed from the same reservoir as the brakes on some model years, from a dedicated small reservoir on others. Check which you have before touching anything, because drawing the brake reservoir below the clutch feed port pulls air into two systems at once. A pedal that sinks to the floor and returns slowly, or one that engages only in the last 20mm of travel, is the classic air signature. The Gunson Eezibleed kit, part number 77008, addresses this by holding the reservoir under constant pressure while you crack the nipple, so fluid moves one direction only and no air gets sucked back on the return stroke.

Setting the kit pressure from the spare tyre

The Eezibleed draws its working pressure from an inflated tyre, and the single most common mistake is over-pressurising. Deflate the spare, or a road wheel, down to 15 psi before connecting. The kit will happily transmit 30 psi if the tyre holds that, and 30 psi against a plastic MX-5 reservoir cap risks a split or a blown seal that sprays DOT 4 across the engine bay. DOT 4 strips paint in minutes, so 20 psi is the ceiling and 15 psi is comfortable. The kit ships with several reservoir caps; the MX-5 clutch reservoir on most NB and NC cars takes the smallest of these, and you thread it on in place of the original cap after topping the fluid to the MAX line. Fill the Eezibleed bottle about one third with fresh DOT 4, connect the clear pressure hose to the cap, then the air line to the tyre valve. Fluid in the bottle feeds the reservoir automatically as the circuit empties, which is the whole point: the reservoir cannot run dry while pressure holds, and that is what lets one person work the bleed nipple alone. Watch the bottle level through its transparent wall and refill before it drops below the pickup tube.

The actual bleed sequence

With the tyre connected and 15 psi showing on the reservoir cap, walk to the slave nipple. On the NB, fit an 8mm or 10mm ring spanner over the nipple first, then push a length of 5mm clear silicone tube over it running down into a catch jar with 20mm of old fluid already in the bottom, so the tube tip stays submerged. Crack the nipple a quarter turn. Fluid runs on its own under the Eezibleed pressure, carrying bubbles you can watch travel up the clear tube. Hold it open until the stream runs continuous with no bubbles for a good 10 seconds, usually 30 to 50ml through the tube, then close the nipple before releasing anything. On the NC concentric slave the process is identical but the union bleed screw sits lower and blind, so a mirror or a phone camera helps confirm the tube is seated. Do not pump the clutch pedal during the bleed with the Eezibleed connected; the constant pressure does the work and pumping only churns the master cylinder. Once closed, disconnect the air line from the tyre first, let the reservoir depressurise fully, then remove the cap. Refit the original cap and wipe every surface the fluid touched with water, not brake cleaner, since water dilutes DOT 4 harmlessly and solvent can smear it further.

One thing that ruins the job

Never let the Eezibleed bottle empty while the nipple is open. The instant it sucks air, you pump that air straight into the line and start over. Keep the bottle above one third at all times.

Confirming the pedal and checking for reintroduced air

Start the engine, hold the brake, and press the clutch fully several times. A correctly bled MX-5 clutch bites in the middle third of pedal travel and returns crisply with no dead spot near the floor. If the first 30mm feels hollow and firms up only halfway down, a small pocket of air remains, most often trapped at the highest point of the line where it loops over the gearbox on the NC. Repeat the bleed with the front of the car raised 100mm on ramps so that high point sits closer to level, which lets the trapped bubble migrate toward the nipple. Some NC owners find the concentric slave stubborn because its internal geometry holds a bubble the Eezibleed pressure alone will not shift; in that case a single gentle pedal press with a helper cracking the nipple, done once after the pressure bleed, usually clears the last of it. Measure the pedal free play at the top of travel too. Excessive slack there points to a master cylinder pushrod adjustment or a failing master seal, not air, and no amount of bleeding fixes a mechanical fault masquerading as a hydraulic one. Fluid coming out dark brown or with grit suggests the slave seal is degrading and the fluid change is buying time, not a permanent fix.

Fluid choice and change interval

The Mazda service schedule specifies DOT 3 or DOT 4 for both brake and clutch circuits, and the two share chemistry, so a bottle bought for a brake pad and fluid service does both jobs. DOT 4 has a dry boiling point around 230C against roughly 205C for DOT 3, which matters more for hard-driven brakes than for the clutch, but there is no reason to run the cheaper spec when they cost within a euro or two of each other. Glycol-based DOT 4 absorbs moisture from the air, and a circuit that has sat three years can hold enough water to drop the boiling point by 40 to 50C, which is why the interval is time-based, not mileage-based. A 500ml bottle of Bosch or Comma DOT 4 covers a clutch bleed with plenty spare for a subsequent brake job, and once opened the bottle should be resealed hard and used within a few months before it draws moisture itself. Do not mix DOT 5 silicone fluid into a glycol system; it does not blend, it separates, and the resulting slug of incompatible fluid can lock a slave piston. The MX-5 clutch takes so little fluid that buying a fresh sealed bottle for each service is trivial insurance against contaminated old stock.

The open question most owners never resolve is whether a pedal that goes soft again within months is air the bleed never fully cleared, or a slave seal that is passing fluid internally and will need replacing regardless of how carefully the Eezibleed is worked.