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Clutch engagement problem


gtom

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Hello 240z community,

So I'm thinking that I need to replace my clutch on my approx. 90K mile, '73 S30 Z with stock 4-speed transmission, but I would like to inquire about the problem on the forum first.

The problem with the clutch is that:

1. With clutch pedal fully depressed, there is a bit of a problem engaging gears, especially 1st gear at rest.

2. Releasing the clutch pedal, clutch engages early in low pedal position, then as power is applied, clutch begins to slip.

3. Releasing clutch pedal further as it moves to a higher position, clutch re-engages fully.

Question:

Do I need a new clutch kit installed to remedy this problem or is it simply a matter of adjustment? If it is adjustment, where should I start?

Thanks much in advance,

gtom

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It sounds like you have a problem with hydraulics. Check the fluid level in the clutch master. If it is low you have leak so look for signs of fluid leaking at the slave cylinder and at the master (look in the cabin under the dash forward and above the pedals). The most likely problem is a worn out master cylinder. Replacing the master and slave as a set is common practice but not essential.

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1. With clutch pedal fully depressed, there is a bit of a problem engaging gears, especially 1st gear at rest. What about reverse? It should be the worst if the clutch is not dis-engaging completely.

2. Releasing the clutch pedal, clutch engages early in low pedal position, then as power is applied, clutch begins to slip. This part doesn't really make sense. It grabs, then slips? Maybe the slave or master cylinder piston is sticking so the fork travel isn't following pedal travel.

3. Releasing clutch pedal further as it moves to a higher position, clutch re-engages fully. Does it slip under hard acceleration?

Some questions above for clarity and possibilities. beerman is right. If the clutch doesn't slip when it's not supposed to then the problem probably lies in the hydraulics.

Edit, after Zkars's post - I've seen it mentioned that bleeding the clutch hydraulics often fixes clutch problems. Might be the quickest, easiest thing to do.

Edited by Zed Head
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If you cannot get the clutch to slip with the clutch fully out (foot off) under any driving condition, then your clutch friction surfaces are not the problem.

Checking fluid levels and for leaks is definitely step one.

I would begin by lengthing the clevis rod under the dash a couple of turns to raise the friction point and see if clutch-applied shifting goes with grinding and friction point become better (higher).

If this works for short while then gets worse, time for a new master.

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Ok, I did my inspections and found:

1. Clutch fluid reservoir is low.

2. Evidence of fluid leakage at master cylinder in cabin. (see photo)

3. Evidence of fluid leakage at slave cylinder when rubber boot was pulled back. (see photo)

4. Rubber sleeve at flexible line at slave cylinder decayed/broken. (see photo)

Question:

Given that I have not bled the system (I recently purchased the car), do the findings above require that the clutch master and slave cylinder be replaced along with the flexible line at the slave?

Thanks again in advance.

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If the master is leaking, it should be swapped. I tend to follow the line of reason that you may as well do both at the same time and avoid having an issue pop up later. The line will obviously need to be replaced, as well.

These parts are fairly cheap, may as well take care of all of it at once.

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If you've got evidence of leakage, I'd replace 'em! You sound on the right track with both cylinders and the flex line. That flex line looks pretty end of lifespan to me.

All those parts are available pretty inexpensively at RockAuto.

As far as clutch friction parts, it's not surprisingly at all if it slips with the pedal partially depressed, clutches are designed to slip when you put the pedal down, what you would need to worry about is if it slips under load when you're not touching the clutch, which you shouldn't be touching the clutch unless you're changing gears (I don't wanna accuse anybody of anything, but just make sure we're at square one in case we need to be! Riding the clutch has worn out many a clutch unnecessarily.)

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OK, sounds good. I'll go ahead and order the parts and replace and hopefully that will solve the problem. I think I'm now on the right track though since my clutch pedal isn't all that firm and the clutch doesn't slip under load. We shall see...

Thanks again for the help!

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Bench bleed the new master, install new slave, hook up the line and you should be able to gravity bleed the slave.

While replacing the interior pin on master rod, look for rounding out of the hole in the pedal where the clevis pin goes thru. Can add some slop when you need to adjust. Might have to add a bushing to tighten it up.

Pretty straight-forward install, couple of fun hours and you'll be well rewarded.

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  • 2 weeks later...

Replaced the clutch master and slave with SACHS replacement parts. The old flexible line was in bad shape. Engagement feels much better, but now I can detect clutch slippage. Oh well, I think its time to replace the clutch. Quick question, will the new master and slave cylinders work with the '81-3 280ZX 5-speed?

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Replaced the clutch master and slave with SACHS replacement parts. The old flexible line was in bad shape. Engagement feels much better, but now I can detect clutch slippage. Oh well, I think its time to replace the clutch. Quick question, will the new master and slave cylinders work with the '81-3 280ZX 5-speed?

All of the NISSAN transmissions use the same hydraulics. Not sure about the BW T-5 in the Turbos.

Make sure the slave cylinder is returning all the way. If the fluid can't flow back freely it will cause that clutch slippage... Is there supposed to be a return spring on the 73' cars?

Charles

The 73 does not have a return spring. The clutch pedal adjustment needs to be correct to ensure proper clutch operation. No free-play between the pedal and master could hold the clutch a bit and cause slipping.

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Make sure the slave cylinder is returning all the way. If the fluid can't flow back freely it will cause that clutch slippage... Is there supposed to be a return spring on the 73' cars?

Charles

Yes, the rod on the master is fully extended on the return position with the clutch pedal at the highest possible point. My '73 does have a return spring on the clutch pedal.

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All of the NISSAN transmissions use the same hydraulics. Not sure about the BW T-5 in the Turbos.

The 73 does not have a return spring. The clutch pedal adjustment needs to be correct to ensure proper clutch operation. No free-play between the pedal and master could hold the clutch a bit and cause slipping.

My '73 does have a return spring and I've adjusted so that the master cylinder rod is fully extended in the pedal return position. There is a bit of free play caused by the wear of the clevis at the clevis pin connection.

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My '73 does have a return spring and I've adjusted so that the master cylinder rod is fully extended in the pedal return position. There is a bit of free play caused by the wear of the clevis at the clevis pin connection.

There should be about 1" of free play at the pedal. See the factory service manual, clutch section, page 6.

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My '73 does have a return spring and I've adjusted so that the master cylinder rod is fully extended in the pedal return position. There is a bit of free play caused by the wear of the clevis at the clevis pin connection.

I think you are talking about the spring on the clutch pedal. The slave cylinders on the Series I 240Z had a spring on the slave cylinder. They also had a special clutch fork with an extra tab to anchor the spring.

You have a 1973 240Z. That is series IV.

Chas

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