Datsun Roadster Forum-311s.org

Hi, this is my first post so please excuse me if I make any mistakes! My clutch pedal would intermittently drop to the floor, but with a few pumps it would build up pressure. Today, however, I heard/felt a "pop" (at the pedal) and then it dropped to the floor (never to come back). Is this the master cylinder or slave cylinder (or other)? Thanks!

Either or probably!
No, seriously, it is a very simple hydraulic system and it sounds like you have lost all fluid due to breakdown.
Have a good look for a fluid leak under the car, check the flexible hydraulic hose and check the state of the slave cylinder for obvious leaks.
My advice is to change BOTH the master and the slave for replacement units with a new hose.
Once one component goes the others may not handle the new pressure.

Sammy66 wrote: ↑Tue Nov 13, 2018 9:20 pm Hi, this is my first post so please excuse me if I make any mistakes! My clutch pedal would intermittently drop to the floor, but with a few pumps it would build up pressure. Today, however, I heard/felt a "pop" (at the pedal) and then it dropped to the floor (never to come back). Is this the master cylinder or slave cylinder (or other)? Thanks!

There is a spring under the dash which should return the clutch pedal back to its resting point. If you have to pump because the hydraulics are malfunctioning, and the spring broke, I could see the scenario you describe.

Master cly seal wrinkle ,fluid breaks down the rubber over time
When the wrinkle straightens out it holds the fluid when it dont look out , same on brakes cly
Its why a brake job on a 2.5 3 ton truck includes new master cly every time it needs pads

Thanks everyone for your great input!

Suggest you get stainless hose, and you might as well replace all the brake lines (3) as well.

Also check the archives about the clutch pedal pin and hole which can get enlarged and ovaled, affecting the clutch arm travel, thus affecting clutch performance. Might as well check all parts of the system, "while you are there".
Linda

spyder wrote: ↑Wed Nov 14, 2018 1:59 am

Sammy66 wrote: ↑Tue Nov 13, 2018 9:20 pm Hi, this is my first post so please excuse me if I make any mistakes! My clutch pedal would intermittently drop to the floor, but with a few pumps it would build up pressure. Today, however, I heard/felt a "pop" (at the pedal) and then it dropped to the floor (never to come back). Is this the master cylinder or slave cylinder (or other)? Thanks!

There is a spring under the dash which should return the clutch pedal back to its resting point. If you have to pump because the hydraulics are malfunctioning, and the spring broke, I could see the scenario you describe.

You were 100% correct, thanks so much for the input! Do you know where the clutch pedal return spring can be purchased? I do not see it on any of the datsun parts online stores?

You were 100% correct, thanks so much for the input! Do you know where the clutch pedal return spring can be purchased? I do not see it on any of the datsun parts online stores?

First,
You should not be able to "pump" a Clutch Master. I you can, you are likely to bend the clutch fork, pop the piston out of the slave cylinder or Both.

The brake master has a residual valve the allows you to pump the brakes, the clutch should not have this valve.

The clutch system is very simple.
Check the fluid in the master.
Check the spring under the dash and under the car.
Check for leaks under the dash at the firewall and under the car at the slave cylinder.