All Things Fiero > Expert Tech Advice

Building the Ultimate Clutch Slave

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TopNotch:
This write-up will tell you how to build a clutch slave cylinder that will last a long long time, and will be easy as pie to bleed. The first part of this procedure is for a 4-speed or Isuzu 5-speed clutch slave. The Getrag slave uses a different size piston, (but I've heard that the Isuzu and/or 4-speed slave can be used with a Getrag). And even if you have a Getrag and don't plan to change your slave, read the part about building a speed bleeder. It makes bleeding your clutch system so much easier. (Many thanks to some people on Pennock's forum who gave me these ideas.)

The below picture shows, on the right, the piston out of a Fiero clutch slave cylinder (4-speed or Isuzu). The piston on the left is for a 1985 Toyota MR2.

Notice that they are exactly the same diameter. The spring shaft on the Fiero piston is longer, but that doesn't really matter. The big difference: Notice that the Toyota piston has two seals. It can replace the Fiero piston perfectly. The piston is held in by a snap ring. Just remove it with snap ring pliers, remove the Fiero piston, and put in the Toyota piston. Then replace the snap ring.

Now for the bleeding part. The bleed screw in the slave is an odd size, and no one makes a speed bleed version of it. But you can make your own. To do this, remove the bleed screw, cut off the nipple with a cutoff wheel, and drill out the center hole with a 17/64" drill bit. Drill down until the bottom of the drill bit is about to the bottom of the threads on the screw. You can use a 1/4" drill bit if you wobble the bit a bit to enlarge the hole slightly. Then tap the hole with a M8x1.25 metric tap. The result should look like this:

Get a Speed Bleeder no. SB8125 or SB8125L bleed screw, and cut off the bottom part of it, about where the side hole is. Then screw it into the tapped slave bleed screw. The result should look like this:

Put some pipe thread compound or Teflon tape on the threads of the new home-made bleed screw, and replace it in the slave. When you bleed, loosen the original screw, not the smaller one screwed into it. That one should stay tight.
After installing the slave cylinder back in the car, do the initial bleeding this way: Push the piston rod in as far as you can, and prop it with a small piece of wood or something between it and the fork lever so that the piston stays compressed. Open the bleed valve about 1/2 to 1 turn. Fill the clutch master cylinder reservoir nearly to the top and pump the clutch smoothly about 3 or 4 times. Refill the reservoir and repeat until you have pumped about 3 or 4 reservoirs full of brake fluid through the system. (The Speed Bleeder will allow fluid to go out, but no air to come in to the system.) Tighten the bleed screw, remove the piece of wood compressing the piston, and seat the rod in the fork lever. Check the reservoir fluid level and put the cap on. Now try your clutch out. It should work perfectly, assuming the master and lines are all good.

TopNotch:
Since doing this, I've learned that you can send any non-standard bleeder screw to the folks at Speed Bleeder, and they will convert it to a speed bleeder, for $7.00. I emailed them for further details, and am awaiting a reply.
Edit: Confirmed. All you have to send them is your old bleeder and $7.00.

TopNotch:
Update: Now you can get a speed bleeder kit that will screw right into the slave. Just order part no. SB-BMW-S from here.

Fierofool:
If you find that the bore on your old slave is pitted and unuseable so that you can't use the Toyota piston, you can replace the slave with a slave cylinder from a 1990 full size Blazer.  It's almost identical to the Fiero part.   Not sure if this part number is GM or not, but it might work as a reference.  Part # SC103483.  This of course is for replacing the Isuzu and Getrag slave.  This slave will probably be in stock, and is much cheaper than the Fiero slave.  Save and reuse your old Fiero push rod. 

Fierofool:
I and some others have had difficulty finding the 85/86 MR2 slave piston rebuild kit.  Advance shows they carry it but no one has ever found it.  If you want the genuine article from Toyota or need a cross reference number, the Toyota number is part # 04313-12030.  It's about twice the cost of auto parts stores listing.  Toyota sells it for around $18 and you can probably get it in hand on your first visit. 

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