1979 Datsun 280ZX
5 Speed
Replaced slave cylinder Twice
Newer clutch master

Hey guys I have done quite a bit of reading and searching to try and find a problem similar to mine but I cannot quite nail it down, so please forgive the clutch post I know there are tons of them.

The Problem:
The clutch pedal is very soft and spongy, while driving and after shifting the clutch pedal will not return all the way up, (about two to three inches of play and its return is very slow) I have to use my foot to bring it back up all the way after shifting.

What I have tried:
At first while driving the clutch lost all pressure and the pedal went to the floor. The clutch could not be engaged.
The levels of fluid all checked out.
So I replaced the Clutch Operating Cylinder (The slave) - after bleeding it and verifying the lines were clean the clutch was operational again. Albeit with the spongy problem after shifting and engaging the clutch. This was remedied temporarily by simply bringing the pedal back up after shifting.
Then all pressure was lost and the same thing happened. Reluctantly I replaced the slave again.
The problem did not happen for a while but the sponginess is getting worse and worse.
Then all pressure was lost one day after driving. So what i did was press down on the lever on the Tranny that pushes on the slave plunger underneath the car. A few presses and we had pressure again. But Again the sponginess is getting progressively worse.

So my question is, what the hell is going on? I would really appreciate a 280zx god to come in and help me
Thanks in advance

 

try replacing the master they are cheap and that should fix it i did the same in my z31T and the new master killed my slave so maybe the same happened just reverse? all you can do is try.

 

Did you replace the rubber line to the slave? Did you flush ALL fluid when you replaced them?

I always keep the bleeder wide open, pump until a steady clean stream, then go to the "pump, open, hold, close" bleeding method.

 

Did you every actually adjust the push rod? You must have seen the threaded fitting on the end of the master cylinder when you installed it.

Do a proper bleed till theirs no bubbles coming out then stick your head up under the dash and adjust the rod out till theres 10mm of freeplay. Its a 12mm nut btw

Good luck!

Oh and if that doesn't work you might have the wrong TO bearing collar!

 

Hey,

I have a Z31 but similar problem.

I ALSO replaced the slave cyl AND Master Cyl...but still funky feeling clutch pedal and I have to use my toe to pull the pedal back up.

I have one other symptom that may or may not be related....
Clutch slip.

But...the clutch slip in my case could possibly be related to a leaking engine Rear Main seal of transmission seal leak.

Been trying to find a solution to this for a while.

Guess I'll try replacing the Master and Slave Cyls again and the Hose at the Slave (again).

I carefully bled it until there was absolutely no air in the cyls nor the lines.

Push rod Adjustment seems right on 10mm.