Reese04

If you thought you knew how to adjust your clutch, watch this short video from Flying Miata. Very good, very short, to the point.
If you have changed out any of the following, then an adjustment is needed. Pressure Plate, Clutch Disc, Master Cylinder, Slave Cylinder, adjusting rod on clutch pedal, adjusting rod on slave cylinder.

Reese04

I just went thru almost 4 days of troubleshooting my hydraulic clutch system. I ended up purchasing a new master cylinder and slave. But that didn't fix the problem. For some reason the master was building up so much pressure that it would blow the piston right out of the slave cylinder on the transmission. I ruined 2 slave cylinders thinking I had the problem fixed, but didn't. I tried adjusting the clutch rod that goes between the pedal and the master cylinder, and it would not take out the pressure. I kept reading about a bypass inside the master. Without going into allot of detail, there is a pressure release valve in the back of the piston, rear part of the piston slotted area. There is a pin that comes up from underneath the housing into the slotted area. When the clutch is at rest, the piston is shoved forward by a large spring in the back, or in the pressure chamber. When the piston is fully forward, the pin from underneath, is supposed to depress the pressure release valve. This allows pressure and fluid from the pressure chamber and from the line and slave cylinder to feed back into the reservoir on top of the master. It took me a long time to learn this. There were no drawings of the Clutch Master Cylinder that Martin sells in his kit, nor any explanations. I just had to tear apart my old master and study it, piece by piece. This was not happening on my master cylinder. You can actually see the pressure release valve and pin through a hole in the front of the bottom of the reservoir when the piston and clutch is a rest. Once you begin to depress the clutch the pressure release valve disappears from view. Seeing this is a great aid in adjusting the clutch rod connected to the pedal. In my case, my entire problem was caused from the clutch rod being too long. So even when the pedal and piston were at rest, the rod was pressing the piston keeping the pressure release valve from being depressed, thus creating more and more pressure with every depression of the clutch. I had to remove exactly 3/16" from the end of the clutch rod to make it work, fixing the problem. Who would have guessed? It has been the same rod installed ever since I built the car in 2004/05. I have always had adjustment problems, but not like they were when I bought a new master cylinder. I believe that some of the valves and seals were going bad in my old master. The clutch pressure would fade allot as the engine warmed up. I installed Dot 4 brake fluid that has a very high wet and dry boiling temp, thinking that would solve my problems. Wrong!!! I highly recommend using Dot 4. Even if water does get into it, it's boiling temp is still allot higher than Dot 3.

Here's another thing. The Master Clutch Cylinder in Martin's kit is actually a Master Brake Cylinder. I researched for days to finally find the right one. So if you are using kit that came with a Master Clutch Cylinder, it is PN: M96481 and is listed for a Datsun 521 Pickup Truck 1972. Everything about it is identical. Cost me about $31.00. Not bad. Make note of it in case yours goes bad. There are several moving parts, springs, seals, valves, and rings that can go bad inside it. I also found a rebuild kit on line for it for a whopping $9.