When the Clutch Goes Squishy

MMMM... Clutch juice!

MMMM… Clutch juice!

So, there I was. Minding my own business. I was at the store to pick up the proverbial bacon and milk. The weather was nice, so I brought Sharka. I hit the start button, put the clutch in, and start to back out. And BAM!!!

I stalled.

I looked around, totally at a loss. I put the clutch in again, to take it out of gear before trying to start the engine, and I notice that there’s very little pressure. The pedal goes to the floor very easily. So I pumped it in hopes that maybe it wasn’t catastrophic clutch line failure like last time. And yay, clutch pressure! So I babied the car on the short trip home. I used the clutch very little, mostly shifting without it. I got home, dumped the groceries, and went right back out in Bucky to grab some clutch parts from the nearby NAPA.

Clutch Master Cylinder Swap

Remove everything around the clutch master.

Remove everything around the clutch master.

First item of business is getting enough room to work. Most Miatas won’t have much problem. A few might have to remove some intake components from around the clutch master. Sharka has the Link ECU sensor pack and the cruise control brain surrounding the MC.

Suck out the fluid.

Suck out the fluid.

Step 2: Suck out the fluid. There’s not much in there, but it will all come out when you remove the hard line attached to the front of the master cylinder. Suck it out with something. I have a small ear syringe (pictured above) that I’ve used for years to drain brake and clutch reservoirs. It lives with my bleeder bottle when not in use.

Step 3: Remove that single hard line at the front of the MC. You need a 10mm flare wrench to do this. You might want to have a plastic baggy nearby to put the end of the hard line into. Also, plenty of paper towels below to help protect your paint.

Remove the master cylinder.

Remove the master cylinder.

Step 4: Remove the MC. It’s held in by only two nuts. Get a 12mm socket and go crazy.

One shiny, new clutch master cylinder.

One shiny, new clutch master cylinder.

Bench bleed the MC.

Bench bleed the MC.

Step 5: Bench bleed the master cylinder. Sorry to not have a photo of me actually doing this. It requires two hands and that left me with none to hold the camera (yeah, my tripod was away on an adventure). The way you do this is very simple.

0: Find a nice big bucket for the fluid to spray and drip into. Also eye protection. Do not skip step zero.
1: Fill reservoir with fluid.
2: Remove cap on the outlet.
3: Using a small rod (a 3/8″ ratchet extension of 6-12″ works great), push the piston into the master cylinder. That will force air out. When the piston comes back, it will draw fluid in. Do this until fluid starts to squirt from the outlet.
4: Replace cap on the outlet. Wipe the MC body dry. Walk back to your car and install it while not dripping any brake fluid on your bodywork.

The goal of bench bleeding is just to get everything wet. You want to get fluid to go through everything. This makes it easier to get bubbles out when bleeding the clutch for real.

Reinstall the master cylinder.

Reinstall the master cylinder.

Step 6: Install your new clutch master cylinder. The easy way to do this is to get both of the nuts threaded onto the shafts sticking out of the firewall. Do not tighten them. Then, with a floppy MC, install the clutch hard line. If you get the clutch master torqued down on the firewall and then try to install the hard line, it will be very hard to get the threads to start correctly. But with some play in the MC, there’s no problem.

Step 7: Wipe everything down with clean, dry paper towels. Make sure no brake fluid is anywhere. It’s not horrible stuff. The world won’t end if you get a drop on your paint and wipe it up right away. But you do NOT want to accidentally leave any on your paint overnight or longer. It is worth the effort and time to make sure no stray brake fluid drops got on your paint.

Step 8: If you don’t need to swap out your slave cylinder, you can move onto bleeding the clutch. Yay!

Clutch Slave Cylinder Swap

Remove clutch fluid

Remove clutch fluid

Step 1: Remove clutch fluid. Why am I including this again? Because in 13 years, I’ve changed Miata clutch slave cylinders a half dozen times. I’ve replaced a master exactly once. You just got done looking at the pix of that one clutch MC job. They just don’t go bad that often.

A fine new clutch slave, ready to get to work.

A fine new clutch slave, ready to get to work.

When you buy a clutch slave, you sometimes get them in pieces like this. And sometimes you’re lucky enough to find a rebuild kit instead of a whole replacement kit. A rebuild kit will come with everything except the big metal body.

If you live in a fairly rust-free environment, always try to get a rebuild kit. If you live in the rustbelt, you’re better off with a replacement kit. The reason is, the clutch slave body will rust internally. It’s hard to scrub off the rust and maintain roundness inside the cylinder. Chances of it leaking again are pretty high. But if your old cylinder has no rust, you can just clean things up and throw new parts at it for about 20% the price of a whole new slave cylinder.

Bench bleed the slave cyl.

Bench bleed the slave cyl.

Step 2: Bench bleed your new slave cylinder. While you don’t really have to do this, it’s very easy. And it makes the bleeding process much quicker once you have everything bolted together again. That, to me, is worth it.

There is nothing to this. It’s more gravity bleeding than bench bleeding. You just pour fluid in the top of the cylinder bore and then let it drip out the two holes in the other end. Pop off the cap (if your kit included one) and let fluid flow out the inlet hole. Then, once you’re happy, plug that hole up and unscrew the bleeder valve to let some fluid drip out of it. Then tighten it up and pour the excess fluid out of the cylinder. SIMPLE!

Just like above, the goal of bench bleeding is just to get everything wet. This makes it much easier to get bubbles out when bleeding for real. Which you’ll be doing very soon.

Removing the old and busted.

Removing the old and busted.

Step 3: Remove the old clutch slave. This is more difficult than the master cylinder, but not much. There are two bolts holding the slave to the side of the engine. There’s one hard line (most Miatas have a curly-q line that’s also attached to the engine) that will require a flare nut wrench. The stock line is 10mm. Sharka has the 949Racing stainless braided clutch line that eliminates the curly-q. This one takes an 11mm wrench.

Do yourself a favor and remove or at least loosen the hard line before you completely remove the slave cyl from the engine. You can see in the photo that I still have one bolt holding the thing on. I was about to remove it and then remembered to do the hydraulic line while still having something to hold things in place at the last minute.

The one on the top is 18 years old.

The one on the top is 18 years old.

Near as I can tell, these are Sharka’s original slave and master cylinders. The car was built in late 94. That puts them at just over 18 years of service. That’s pretty incredible in my humble opinion. I did 5 slave cylinders on Sharka-the-97 in 8 years. That is not so incredible. Or maybe it’s incredible for different reasons.

Step 4: Reinstall the slave cylinder. There’s really nothing to it. If you laid out your parts and tools, you didn’t even have to get up out of the wheel well to get the new slave cyl from being bled earlier.

Bleeding the Clutch

My high dollar brake and clutch bleeder.

My high dollar brake and clutch bleeder.

Yes, really. What, did you expect something awesome? A crazy power bleeder system? Some kind of funky gravity bleed method? Those so-very-breakable Speedbleeder screws? Nope. I use THIS. It used to be a Diet Coke bottle. It’s been in my garage for about 15 years.

The only special component is the hose. You need one sized to fit over your bleeder screws. It also helps for said hose to be transparent so you can see bubbles coming out of the bleeder. That’s it. The rest of the parts can be found around your house. A bleeder bottle like this is well worth the 5 minutes it takes to make.

The tip of the syringe fits in the gap between the bottle and the hanger when not in use. And when not in use the whole thing just hangs from a shelf in the garage. I leave a little fluid in the bottom of the bottle.

Bleeding rig ready to go.

Bleeding rig ready to go.

Open the valve, have your assistant press the clutch pedal. Then close the valve while their foot is down. Then let them lift. Then repeat. Keep in mind that the fluid reservoir is pretty small. It will need to be filled after a 8-10 presses.

Oops! Almost forgot to mention my assistant!

My assistant.

My assistant.

Just over a year old and already getting filthy in the garage with dad. She’s such an angel.

I hope this helps someone out! And if these NAPA parts last even half as long as the originals, I’ll be a happy guy.

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  • Chris B says:

    Did the clutch slave on my brother’s car and boy was it messy. I wish I had this write up when I did it. Still not as bad as when my clutch master, slave and CAS all went bad within a day of each other. That was an interesting week.

    • revlimiter says:

      HA! Yeah, I’ve had brake fluid spray out while I was bleeding the clutch before. I *thought* I had that bleeder screw tightened. Since then I’ve always worn glasses.

      One time, I was installing a supercharger on Sharka. Took a test drive and came back and the water pump decided at that moment to go away. Leaking everywhere. Fortunately, I had all the stuff to fix it in the garage at the time.

      Gotta love cars.

  • spindiscs says:

    Eight clutch slaves gone!
    Seems a bit excessive. What are you using for fluid – diet coke?

  • GT-Alex says:

    When my slave began to die, I started feeling the symptoms 70km away from home.
    50km from home, I failed getting a gear in until complete stop. I manage to get back on the road.
    30km from home, the resistance of the pedal has dropped severely. I try to avoid using the clutch at maximum, staying in 4th, reving to the right rpm to change gears if needed.
    300 meters from home. Last roundabout. There’s a car engaged, I have to stop. I stall. The pedal doesn’t have any effect anymore. I managed to start the car again with 1st gear on and drive it in my garage.

    Now, I know that when it breaks, you can do about 60km before you don’t have anymore clutch fluid. And as it takes only 3 screws to change that thing, I might keep a spare slave with me for road trips 🙂

  • meGrimlock says:

    hey, I have a 2003 2.0L protégé which shares the reservoir for both the brakes and the clutch. is it necessary to bleed the brakes after a clutch slave/master/line install? also since it shares the same reservoir, how does one bench bleed the clutch master cylinder? do I need to remove the brake master cylinder just to bleed them both or can I bleed once it is attached to the firewall? thanks.

  • Mike says:

    Just used this how to yesterday, I have a tip that makes it way easier for reinstalling the master cylinder to the hardline.

    Instead of loosely putting it on the two bolts before connecting the hard line, pop the hard line out of the little plastic clip. Then screw the hardline on with the master in your hand. Then put the Master onto the two bolts and screw it down. This lets you adjust the angle really easily and get it threaded on in seconds, before I did this I was trying to thread it on for 10 minutes since my line was at a very large angle. I ended up losing all the brake fluid from the reservoir. =(

    Thanks for the write up.

  • Tim says:

    Thanks for this…. it really helped me out!

  • Brian says:

    My slave has been slowly leaking for a couple years, but I just kept adding brake fluid and I was good to go…until yesterday when no amount of fluid made my clutch work. Fortunately I made it home, trolled the internet, and purchased a slave cylinder at my local parts store. The hardest part about replacing the slave was reconnecting the hydraulic line to the new slave. The slave is kind of hard to reach, it’s a one handed job all the way. Anyway after spending a half hour trying to hook the hydraulic line while the slave was tightly bolted, then loosely bolted, I finally removed both bolts again, crawled under the car so I could hold the slave with one hand and thread with the other and in about ten seconds it was connected. My car runs like a dream now! Thank you everyone for your posts.

  • […] Re: 1997 M – Warbird Edition 05-23-14, Mileage- 97,780: Warbird is flying once again now that I changed out the clutch master cylinder, slave cylinder and went ahead replaced the "curly" rigid line from the slave to the rigid line on the fire wall which also includes a small rubber line and of course new fluid in the form of Motul RBF600 brake fluid that I had left over from my brake job on my NB. The job is easy enough but the biggest pain is that stupid "curly" line which I couldn't get a good angle to disconnect the rigid line from the slave to the rubber line, so I finally just bent the line straight to get it out. In all it probably took 2.5 hours(I never rush when I'm working on my car) from the time I got the tools out to the time everything was picked up and packed up in the trunk, thanks to my cousin for the assistance with bleeding the line and letting my use your place to do the work! Stock, more than likely factory master cylinder with very dark fluid which from what I read means it was probably the seals on the slave but then again if it was the original fluid… :bang: Removed air box intake tube and alarm horn to get to the master cylinder. How black do you like your "coffee"? hno: One 10mm nut for the rigid line and two 12mm nuts later the clutch master cylinder is off. OEM unit vs Exedy clutch master cylinder from Treasure Coast Miata Wasn't sure how important that paper gasket was but the new unit didn't come with one and I managed to get the gasket off the OEM unit so I re-used. Stock OEM slave master cylinder just taking up space and not doing it's job:realmad: Remove 10mm nut on the rigid line, one 10mm for the bracket holding the line and two 12mm bolts holding the slave cylinder and its off! Stock OEM unit vs Exedy slave cylinder w/ ss braided clutch line from Treasure Coast Miata After probably 30 minutes of hassling with the rigid to rubber clutch line above the transmission… I just bent the curly line straight to remove since I'm replacing the curly and short rubber line with a ss braided clutch line from Treasure Coast Miata. Stock OEM "curly" line and rubber line vs ss braided clutch line from Treasure Coast Miata Why the made the stock one so long is beyond me… New Exedy slave cylinder installed New ss braided clutch line installed… …but apparently not tightened as I find out once we are trying to bleed and it "seems" there is fluid coming from above the slave cylinder.:bang: After a few minutes of pumping bleeding the clutch pedal felt better than ever and transmission "seemed" to shift easier. Thanks to Adam aka Revlimiter for another well done step by step how to! https://revlimiter.net/blog/2013/01/m…ter-slave-cyl/ […]

  • roy hernandez says:

    Thanks your a life saver. I got my self into doing a bleed job and didnt kno where to start. I had bean putting off until i could find some direction and know how and thats exactly what i found here thanks agin. Roy H san.anton tx

  • Patrick says:

    Thanks for the writeup! Which ones from NAPA did you get? The NAPA branded ones or the Ultra-8 ones? There seem to be a big difference in prices for these parts and I’m wondering if spending more is “worth it”. Thanks!

  • Transporte de carga says:


  • Anthony D. says:

    Your experience is really helping others. Thanks for sharing such effective type of experience.

  • Mark C says:

    Brilliant !! Thanks

  • Lucas says:

    Doing it right now. Write up is a huge help

  • Sang says:

    Hey revlimiter, is it necessary to jack the right front of the car up for this maintenance?

    • revlimiter says:

      It’s pretty hard to get to the clutch slave unless you have the right front off. If you have a lift, you could do it that way, but… yeah. You have to somehow get to the stuff behind the right front tire to swap the slave cyl.

  • H B says:

    Thanks for the write up. I had a unnamed parts house tell me my car did not have a slave. I even showed them a picture of the part on the car. He told me it did not come with my Miata. That it was a add on. I went some where else an it took them the next day to get the part in. Get right up. Had my 16 year old daughter read it to.

  • Richard J says:

    Thanks very much for this. oddly enough I also needed to change the master having first changed the slave cylinder. I did notice the fluid was darker than normal in the reservoir – maybe this indicated the master seal had gone?

    In terms of access, I was able to bleed the system without removing the wheel, though would suggest to change the slave cylinder the wheel needs to come off (and I suspect also to loosen a sticky bleed nipple)

  • Andrew M says:

    hey revlimiter, first off, thanks for the write up as it is very informative, second, i have a quick question.

    Background: i just had my clutch slave cylinder replaced yesterday which solved my low catching clutch pedal and slow release of pressure or so i thought. driving around later last night, i had the same type of thing happen with the pedal. i presume it is the master cylinder now.

    Question: if i pull the line off of my old MC and put it in a little bag with fluid, can i just put new fluid in the NEW MC reservoir and press the piston til fluid comes out the line hole and not have to actually bleed at the slave?

    • revlimiter says:

      Sorry, but I have the news you didn’t want to hear. You always have to bleed the slave. It’s not possible to quickly rig something up and beat the air from getting in the line. Air will get in while you’re unscrewing the line from the MC and again when you’re reinstalling it.

      Fortunately, it’s super easy to bleed the clutch. All of 2 minutes.

  • Skip says:

    This was very helpful in preparing to replace the master cylinder on my ’95 M-Edition today. Thanks for taking the time to document and post the directions and photos! One note about setting out tools: the bleeder valve is 8 mm, at least on my car. My clutch is back to working just fine. Thanks, again!

  • Jonathan says:

    I changed all that, but stilll when i put it on reverse and try to let go of the clutch with out pressing the gas itll go, but once i press the clutch completly and press the brake it shuts down, any suggestions??.

  • Justin says:

    Thanks for providing this reference material. Helped replace both on my new to me 2000 Miata. Best wishes!

  • […] a bottle of brake fluid for the clutch. Even though I have the service manual, I elected to follow Revlimiter's awesome write up here. That is the inside of the clutch master reservoir, after I drained and removed it. What you […]

  • Samuel says:

    So the things listed in the pics is all u need correct?

  • Jane Beatty says:

    my clutch went to floor and i just refilled it . will replace line as im sure its a leaky hose or something like that.

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