Clutch Problems

[240zGraham73]

Hey everyone, I'm driving my 73 240z and while shifting into fourth gear the clutch suddenly stops working and I am unable to get it into any gear. After getting it home and upon further inspection it appeared that the master cyclinder for the clutch has failed, at least that's the best guess and just want to make sure before we order a new one.

So when I press on the clutch it is completely limp and we bleed the master cylinder and it was really dirty, it was a greenish brown color. When the clutch pedal is pressed on you can still see the operating cylinder pushing the push rod, but the pedal still as no pressure. Just to make sure this year doesn't come with a dampner or a slave cylinder, right?

Any ideas were to get a new master cylinder would be great too, local auto parts store said they could get one to me for about 60 to 70 bucks. Thanks a lot for reading and any suggestions. Just want to get her back on the road soon, miss driving it:cry:

[justaZcarguy]

Hey Graham,

There is a slave cylinder on the bottom of the transmission, near the front, I want to say the passenger side.

You will see it attached to the tranny with 2 bolts (10mm bolts I believe), it pushes the clutch fork to pivot it and push on the pressure plate.

I would check that first as it is usually the culprit. You will see little or no movement pushing the fork if this is the problem.

The good news is, they are somewhat easy to replace and not that expensive.

Let us know...

~Brian

[240zGraham73]

I'll have to go check it out tommorrow. I could be confused on what is what but one of the cylinders is getting 2 inches of movement (guess) pretty sure its the master, but not positive. I think I will just buy the slave and the master cylinder that way I dont have one break as soon as the other one is fixed:) thanks for the help, I'm new to the z cars, always loved'em though. Think JCWhintney would have these?

[justaZcarguy]

The Master is up on the firewall and and the slave is on the bellhousing, replacing both is good insurance!

I am not sure that I would use JC Whitney personally, I think that I would hit up NAPA if you could...

Once you pay the shipping and such it is going to be close. Plus, NAPA is always good about exchanging the parts quickly in the event that you get the wrong part.

You may hit up CarFiche.com and download a 280Z manual and check out the clutch section, even tho these manuals are 280Z oriented the clutch and other sections are applicable.

Here is the link http://www.carfiche.com

In the event that you need help, please let me know.

~Brian

[Bonzi Lon]

I would suggest getting a new clutch hose also. This rubber hose fits the slave cylinder to the hard line. They tend to crack and weather rather quick in my opinion. Check your brake lines at the wheels because they are of the same material and subject to the same environment. Braided stainless steel lines all around would solve that problem and look nice at the same time.

Bonzi Lon

[Carl Beck]

Ok -

New Clutch Master

New Slave Cylinder

New Rubber Line between the body and the Slave

Fill with DOT 5 Silicone Brake Fluid. The Silicone will not absorb moisture out of the air like DOT 3/4 Brake Fluid, and it will help preserve all the rubber seals in the Hydraulic Clutch System. My original clutch master and slave lasted 30 years this way. (bought my 72 240-Z new and still have it).

If you replace all three parts at one time - and use a little Silicone to flush out the hard lines from the Master to the Slave, before hooking up the Slave - you can switch to Silicone. DOT 3/4 are not compatible with DOT 5. Also make sure you buy pure silicone DOT 5. (not just something compatible with it).

Do it right once.... Also agree - either use NISSAN OEM parts or NAPA's best... you have to tell the NAPA Parts Countermen that you want their best replacement parts - not the cheapest they handle...

FWIW,

Carl

[Carl Beck]

Oh.. btw .. I hope you are correct about it being the clutch master/slave.... but you should be looking at the slave - while someone else pushed the clutch - to see if the slave is able to move the clutch fork or not. If it is moving the clutch fork about an inch and half - then it's not the clutch hydraulics that are the problem.

Did you notice if the Clutch Master was very low on fluid or not, when you first looked at it? Does the fluid leak out quickly if you refill the master ?

FWIW,

Carl B.

[240zGraham73]

Hey Carl

It looks like the clutch fork is moving, so any ideas what else it may be?

[240zGraham73]

The Clutch Master is full and is holding but when the clutch went it was getting pretty low.

[GreenZZZ]

Fill with DOT 5 Silicone Brake Fluid. The Silicone will not absorb moisture out of the air like DOT 3/4 Brake Fluid, and it will help preserve all the rubber seals in the Hydraulic Clutch System. My original clutch master and slave lasted 30 years this way. (bought my 72 240-Z new and still have it).

Doing some googling about DOT5. You think this conversion process is overkill?

http://www.type2.com/library/brakes/dot5.htm

[Carl Beck]

If the clutch master is holding the clutch fluid - and the push rod at slave is in fact moving the clutch fork rearward about an inch and half..... all that is working at this point.

If the clutch master was getting low - due to a very small, slow leak somewhere, when you were driving the car - then when you pushed on the clutch pedal to shift gears - the clutch itself may not have been fully disengaging at that point.... and you could have damaged either the clutch itself or the transmission.

Since you said that the clutch pedal offers no resistance (even after bleeding it, even with all fluid levels full)..... I'd have to guess that the clutch disc or the pressure plate itself failed.

With a good transmission - it is possible to start a 240-Z in first gear - and let it roll forward, then to build the RPM's up to around 2800... and shift it from 1st to 2nd with no clutch... This however is something that takes some practice, to get the right feel for the needed RPM's etc. .... Not something that is easy to explain, nor walk you though with words here... If you can start it in gear, and shift from 1st to 2nd without the clutch - then you know the tranny is OK, and it's the clutch itself that when out...

But like I said - it is not something you want to try to learn with the car in its current condition...

It won't hurt anything to go ahead and change the clutch master and slave out at this point - but if that doesn't do it - you'll more than likely have to pull the tranny and inspect the clutch assembly.

FWIW,

Carl

[Carl Beck]

Doing some googling about DOT5. You think this conversion process is overkill?

http://www.type2.com/library/brakes/dot5.htm

It might not be overkill , IF you were converting to DOT 5, while retaining all the original parts. Frankly I wouldn't bother at that point. I'd just flush the brake system with clean DOT 3/4.

I do convert the brake systems on my cars, the first time I do a complete rebuild of the brake system, and I only flush out the hard lines with DOT 5... I've never bothered to clean them out with alcohol and blow them out with air... I've always felt that the pressure exerted by the brake master/and your foot on the pedal - forced the DOT 5 though the hard lines with enough pressure to clear out all the old DOT 3/4...... I could be wrong, but in 35 years I've never had any problems result from that process.

Most of my 240-Z's sit a lot, it is very humid here in Florida all the time.. and if I don't convert to DOT 5 - I have to replace or rebuild the rear wheel cylinders every couple years (they are getting very expensive!!). Being aluminum, the rear wheel cylinders are only repairable (rebuild-able), IF you catch them before the corrosion has pitted the cylinder walls... which usually is not the case. Also the front calipers do tend to hang up and drag when left sitting with DOT 3/4 type fluids. That too has been eliminated by the use of the DOT 5.

DOT 5 is NOT recommended for competition use - where you are going to heat the front brakes up to the point that it melts the bearing grease etc... Besides, you change the brake fluid after each track event anyway..

FWIW,

Carl B.