Clutch Failure

[Caslin]

72 240Z all original. clutch pedal failed (pushes down easily) does not allow shifting in gears. Transmission will engage in all gears when car is off and no clutching. Is this likely a cable loose? If so, can a novice mechanic repair it?

Thanks

[Zed Head]

Search "slave cylinder".

It is a relatively easy fix. Most people recommend doing the master cylinder at the same time, since it could be either, and the master usually goes soon after. They tend to fail from corrosion, from moisture intrusion, causing debris and a rough surface, which wears out the rubber seals.

[Bruce Palmer]

I'd guess hydraulics. Master Cylinder or slave cylinder have lost seal and cannot keep pressure. This is not a cable actuated system. If the master cylinder reservoir is empty of fluid you're done.

Look at the slave cylinder under the car and see if it is wet with brake fkuid. If no, check inside of the cabin and see if the firewall is wet with brake fluid.

Thus endeth again why replacing all things rubber AND HYDRAULIC when you come into posession of an old car is a good thing.

[Carl Beck]

Does "all original" also mean it has been sitting for years or several months between being driven?

If so - the clutch discs can freeze/rust themselves to the flywheel. The resulting symptoms can be the same as a hydraulic failure. In this case, you will have fluid in the Master and when someone pushes on the clutch pedal - you can see the push rod on the Slave Cylinder move outward about 3/4".

As mentioned - first check the fluid level in the Clutch Master Cylinder - if it very low to dry - first try filling it with fluid, then "bleed" the hydraulic system. You bleed the system by having someone sit in the car, pump the clutch pedal slowly and easily two or three times, then hold the clutch pedal to the floor. While they hold the clutch pedal to the floor, you crack open, then close the little "bleeder valve" on the slave cylinder. {takes a 10mm box end wrench}. The first few times you should get nothing but air out of the bleeder valve. After a few times you should finally get nothing but fluid out.

At that point the clutch should work - as mentioned check for leaks. If the clutch isn't working, have someone sit in the car and slowly push the clutch pedal down - as you watch to see if the push rod on the slave cylinder is moving out - it should move out about 3/4". If it isn't moving, your slave might be gummed up/corroded. If you do replace the Master and Slave cylinders - replace the rubber hose between the body and the slave as well.

FWIW,

Carl B.

[esmit208]

72 240Z all original. clutch pedal failed (pushes down easily) does not allow shifting in gears. Transmission will engage in all gears when car is off and no clutching. Is this likely a cable loose? If so, can a novice mechanic repair it?

Thanks

If you have a Haynes Manual and a few sockets between 12MM and 13MM maybe a 14MM even a novice mechanic can do it. But judging from the terms you used (clutch cable) you could use a hand from someone knowledgeable. The slave and master cylinders are not difficult to replace but they must be bled atfterwards to ensure all air has been evacuated. Get some help and a good manual for starters and pay close attention to this forum. It will help a lot.

[Caslin]

Thanks to everyone for their help. The master cylinder is empty so tomorrow I'll be looking at the operating cylinder (slave cylinder). The master cylinder was replaced t some point (previous owner left all the replaced parts with car).

Thanks again.