Hi. Have a 64 3.4 MOD with clutch problems. Coming home the clutch pedal bottomed and clutch did not release. Got under the car and slave cylinder was leaking heavy. No leaks elsewere. Bought a new aftermarket slave cylinder which I fitted. Bled the clutch, but not able to get it work properly. Have to pump the clutch twice before it operates. Then if using the clutch again within a few seconds its ok. Waiting more than 4-5 seconds have to pump pedal twice. Have a feeling air is trapped somewere or something wrong with clutch master cylinder which I have not touched yet. ( sticking valve? ) Think it unlikely that master and slave should fail at same time.
First time I bled the system I was using very light vacum on the bleeder screw as I was alone. Could this have caused harm to master cylinder?
Later also tried to bleed it «normal» way with a helper operating clutch pedal, apparently succesful as after a short while no air bubbles. And I’m familiar with bleeding procedure. Have bled numerous brakes and clutches with no problem.
Also tried another old slavecylinder which worked when I took it out from an E type then overhauled. They are identical - long type.
Should my car have the short type? Does it matter? 64 with Moss box.
Certainly have to take master cylinder out, but does anyone have any idea?
Rgds Harald
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Last edited by Norton on Thu Jul 14, 2022 4:29 pm, edited 1 time in total.
After I replaced the clutch hose on my S, the clutch felt spongy. It worked, but didn't engage constistently on the same spot. I bled the system a couple of time with an assistant, but couldn't get all the air out. Then I got myself a one man type vacuum bleeder and that did the job. My clutch has been great since.
Thanks, maybe I shold have kept on bleeding the system. But today I took out the master cylinder and dismatled it. Found no obvious fault, had not been leaking to the outside and rubber seals looked ok. But quite a lot of dirt in there. So if nothing else, it now have a good clean out. Will be putting in new seals etc before assembly. Maybe dirt caused valve not to seat prperly, or air in system. Hopefully it will be working when back in place.
Harald
Due to modern not quite to spec rubbers. Make sure that the master cylinder is not just pushing fluid back into the reservoir.
Due to slight angle I found it was easier to bleed with the nipple at the top. Drillings in my slave cylinder were identical. That got the last bit of air out.
Slave Cylinder2 mine.jpg (2.26 MiB) Viewed 834 times
Thanks.
Master cylinder now rebuild with new rubbers and seals, and fitted. Bled system with vacum. Still same problem, clutch spongy on first push ok on second push. After a few seconds have to push pedal twice again to release the clutch.
Bleeder screw was at bottom and feed line at top. I have switched them around, bleeder now at top.
Maybe as Glyn sugests, master cylinder are pushing fluid back into reservoir. Then the valve inside is not function properly. Have to investigate further with some extra help. Will also bleed it again with a «clutch» operator. Maybe with vacum at same time..?
Try the good old standard bleeding method without vacuum. e.g. Some brakes don't like being pressure bled like Dual booster Lockheed Bonaldi brakes on an Alfa. You will never get a decent pedal pressure bleeding ~ you have to bleed conventionally ~ The joys of classic cars.
Have someone observing signs of fluid being pushed back into the reservoir. I had to shave my brake piston marginally to operate with modern rubbers. Whole story in my thread. One minute I had brakes ~ next minute the pedal went to the floor. I measured a mountain of rubbers. They were all the same.
Finally solved clutch problem on the -64 "S" type. We like to blame Previous Mechanics, here I have to admit Present Mechanic also was a little out. When I dismantled the slave cylinder I noticed the return spring was missing and ordered that together with a new slave. Putting all back together I adjusted pushrod to same lenght as the one I removed. Also readjusted pushrod BEFORE fitting return spring. It is there to ensure the thrust bearing is not riding on pressure plate. The thing is the piston in slave cylinder was starting to operate the clutch from about midposition. And with no return spring, clutch springs returned piston to that position. With return spring now added that one continued to push piston into cylinder, but at a SLOW rate. Next time piston had to travel a longer distance to release clutch - push twice. ( first push spongy, as it did no real work ). This dawned on me standing under the car while an assistent operated clutcpedal at my command. And thinking throug what I had done and more specific, what I had done differently. ( Return spring ). Pushrod have to be adjusted while piston is at bottom of cylinder with spring off!
I could and can observe that a small amount of fluid is pushed back into reservoir at initial travel of clutch pedal. But I think this is normal. It will happen until the valve ( 42 & 41 on parts list ) closes. Think it need to be open to allow fluid into operating cylinder to keep it topped up.
A lot of unnecesarry work, maybe. But now the whole system is overhauled, cleaned and flushed. Was a lot of dirt in there, and I have a totally overhauled clutch hydraulic!
Two different slave cylinders were fitted to the S Type. Short approx 80mm ~ Long approx 95mm (so called hydrostatic cylinder). Long cylinder does not require external return spring & is for diaphragm clutch although they changed the cylinder first ~ They did not coincide. I have a diaphragm clutch but have also kept the external spring to increase thrust bearing life.
Glyn, That is exactly what my shop did when I upgraded from a spring type clutch to a diaphragm type. My November 1964 production car had a flywheel drilled for both types.
My flywheel is also drilled for both spring & diaphragm pressure plates.
