84 720 pickup clutch fluid system repair issues

[84seven20]

Hey y'all,

 

I'm having some trouble repairing my clutch fluid system on a 84 720 pickup that I picked up as a project. My repair started with a soft clutch pedal, it wasn't engaging the clutch mechanism correctly and I could not shift gears with the engine running. I bled the clutch system to no avail, then replaced the master and slave cylinder and things worked! I was able to shift into gears and drive around the block a few times, even down to the tire shop to get a valve stem replaced.

 

Well, it sat for about a month and upon trying to start and drive it again I couldn't put the truck into gear with the engine running. I found a small clutch fluid leak where the soft clutch hose meets the slave cylinder next to the transfer case. After tightening that down and bleeding the clutch fluid system again, I still couldn't get the truck to shift into gear with the engine running. 

 

I ordered a new clutch hose and plan on replacing that. Can anyone recommend anything else to try? 

 

Thanks for the help!

[]2eDeYe]

It's likely the hose is bad and will solve your issue. 

 

It's is usually a good idea to replace the hose along with the master and slave on an older vehicle. All the rubber components are old and a new component in a pressure system will easily blow out the old rubber. 

Inspect the hard lines for rust, cracks and leaks as they may also need to be replaced. 

[datzenmike]

Did you keep the original master and slave? The problem may just be the hose. These are probably original Nisan parts and better quality that the new Chinese made crap.

[84seven20]

Thanks for the advice y'all! I did keep the old master and slave and the old slave is busted for sure. I will replace the hose and give y'all an update, thanks for the advice!

[captain720]

54 minutes ago, 84seven20 said:

Thanks for the advice y'all! I did keep the old master and slave and the old slave is busted for sure. I will replace the hose and give y'all an update, thanks for the advice!

Busted as in it split in half or the seals need redone cause you can often do seals yourself and keep a higher quality Nissan part.

[datzenmike]

Ten years ago I did just that $12 CDN replaced the seal, spring, nipple and rubber cap, dust seal. Everything but the casting, push rod and piston.

[bottomwatcher]

My repair using the seal kit never seemed to last very long. The slave cylinder is exposed to the elements a lot more than the master. They are considered wear parts like clutches and brakes and recommended a full change our when doing the clutch. Just source Japanese when you can. Auto Zone parts are only good in a pinch.

[Ciciro]

I have this same truck and I've always fought with the clutch.

 

What I did to end the issues

 

#1 Replaced every clutch part with Exedy parts. There a Japanese Company that makes the best clutch parts In my opinion. The stuff from the store was always cheap in a bad way. Ironically Exedy parts ended up costing less.

 

#2 cleaned out the clutch dampener with only a rag and dipped the parts in clutch fluid before I re-assembly and bleed that part last.

 

#3 used a high quality clutch fluid

 

#4 made sure to have 1 inch free play in the clutch petal

 

I don't know if it was one of these things or all of them but I finally won the war.

[datzenmike]

Nissan original parts would also have solved the problems. Poor quality after market shit is from China.

 

You can also throw the clutch damper away and join the lines together.

 

One inch play is 8 times too much. You might even be not disengaging properly and wearing out your synchro rings. 1/8" is lots.

[84seven20]

Hey Y'all, 

 

Here's an update. I just replaced my soft line and bled the system again but the clutch still won't disengage so that I can shift into gear with the engine running. (I took a break from the clutch problem and changed my transmission, transfer case, and rear diff fluid.) I took a closer look at the hard line and couldn't find any holes or leaks and double checked the clutch pedal play which is about 1/8 inch. 

 

It's strange because the clutch pedal doesn't feel soft and when I'm bleeding the slave cylinder I can see it move a good amount. The aftermarket slave cylinder (power torque) I got from O' Reilys has started squeaking for some reason so I'm thinking maybe it is that? I also haven't taken apart or rebuilt the clutch damper yet; I've heard you can delete that but it seems like you would have to bend the hard lines towards each other and I'm worried about damaging them. Also, when I've been bleeding the system I start with the damper and then bleed the slave.

 

I took a look at the old master and slave that I replaced, the slave's dust seal is torn and the piston wont move if I push on it. When I replaced the slave cylinder originally I knew it was broken because the pushrod wasn't moving at all.

 

I'll take a look at Exedy parts and try to find some nissan OEM parts too. 

 

Thanks for the help everyone, I'm looking forward to figuring this out!

 

 

[84seven20]

Turns out Exedy isn't making the replacement slave cylinder that I need anymore 😕

[datzenmike]

Slave push rod should move 1.18" (give or take a few mm) See if your getting at least an inch.

 

 

I take it this has never ran properly? If so it may have been put together incorrectly. All master, slaves and clutch arms are pretty much the same but pressure plates come in all kinds of different heights. To compensate, the collar that holds the release bearing comes in different lengths. Someone may have put a shorter one in and this is why the clutch does not disconnect. 

[84seven20]

2 minutes ago, datzenmike said:

Slave push rod should move 1.18" (give or take a few mm) See if your getting at least an inch.

 

 

I take it this has never ran properly? If so it may have been put together incorrectly. All master, slaves and clutch arms are pretty much the same but pressure plates come in all kinds of different heights. To compensate, the collar that holds the release bearing comes in different lengths. Someone may have put a shorter one in and this is why the clutch does not disconnect. 

 

I will measure the slave push rod movement!

 

Prior History: I got this truck for $300 a few months back with a seized engine from sitting for about 5 years. I unseized the engine, cleaned the carb, and got the engine running but couldn't get it into gear. I replaced the clutch slave cylinder and master cylinders due to a soft clutch pedal and was able to drive it maybe 3 times without any evidence of the mechanical clutch components being bad. 

 

So yes, it has never really ran properly while I have owned the truck, but it has ran and the clutch has worked correctly (if just for a short bit) while I've owned it!

 

I am wondering if the problem is a bad clutch damper. When I bleed the damper the fluid comes out nice and clean but when I bleed the slave the fluid is noticeably dirty. Do you think that could be causing the problem?

[datzenmike]

Ah yes the damper. Correct bleed first then the slave. Pump clutch 3-4 times and hold, open bleeder to let out fluid and or bubbles, close bleeder, let clutch up slowly. Repeat till no bubbles.

 

Try bleeding one more time then check the slave push rod for one inch or just over of movement. If everything checks out this would leave the pressure plate and /or clutch disc.

 

A damaged PP or disc rubbing the spinning flywheel will give the same symptoms. I've had one of the springs around the center of a clutch disc fall out and jam the pressure plate. Have seen the friction material de laminate and rub the PP or the flywheel. I stored an engine once and I guess it got wet. Disc rusted to the flywheel.

[84seven20]

19 minutes ago, datzenmike said:

Ah yes the damper. Correct bleed first then the slave. Pump clutch 3-4 times and hold, open bleeder to let out fluid and or bubbles, close bleeder, let clutch up slowly. Repeat till no bubbles.

 

Try bleeding one more time then check the slave push rod for one inch or just over of movement. If everything checks out this would leave the pressure plate and /or clutch disc.

 

A damaged PP or disc rubbing the spinning flywheel will give the same symptoms. I've had one of the springs around the center of a clutch disc fall out and jam the pressure plate. Have seen the friction material de laminate and rub the PP or the flywheel. I stored an engine once and I guess it got wet. Disc rusted to the flywheel.

 

For sure. I'm hoping it's not the PP or anything mechanical in the clutch but it's looking like this might be the case, especially considering how long it sat. My plan now is to take the damper out and clean that as thoroughly as I can to see if that's causing any issues. I have the coupler for the damper delete so I'm thinking about doing that as well, but I might wait to do that so I don't make troubleshooting any more complicated than it already is. I will bleed again and measure the slave pushrod movement, if that looks good but things still aren't working then I'll drop the transmission and dig into that. 

 

Thanks for all the help y'all, especially you datzenmike!

 

 

[84seven20]

Is there anything else you would recommend I replace if I'm going to drop the transmission anyway?

[datzenmike]

Yes the rear seal, the pilot bushing and of course the release bearing. The rear seal you can do in the truck but easier out. The other two are used and you don't know the mileage on them, may even be original. It would be prudent to replace these now rather than having to pull the transmission, again, in 6 months.

[84seven20]

Hey y’all, 

 

Spent some time working on things today. Took off and bypassed the clutch damper, cracked it open and it was full of black sludge. Bled again and checked for leaks but no luck, measured the slave push rod movement and it was only about 17mm at most... (just over a half inch), so this is nowhere near the 1.18” that I should be getting. I tried to move the clutch lever a bit further with the clutch pedal fully pressed down (and bled until no bubbles at all) but couldn’t get it out any further. I even tried a new slave cylinder but that one had a leak at the bleeder screw hole, what a waste.

 

Since I’ve bled and bled and bled and bled, quadruple checked for leaks, and bypassed the clutch damper, i’m thinking that the problem must be with the clutch disc or pressure plate. Planning on dropping the transmission soon to figure the damn thing out. Does anyone have any recommendations for me at this point? This damn thing is driving me crazy.

[datzenmike]

Make sure you have about 1/8" of clutch pedal play before the push rod begins moving. Use a flash light a look up under the dash.

 

Watch the rubber flex hose while depressing the clutch pedal. Is it swelling???

 

 

If something was jammed and only allowing 1/2" of slave travel the pedal would only travel 1/2 way and stop well above the floor. You haven't mentioned this so I would say not jammed.

 

 

[84seven20]

Hey y'all,

 

Taking another look at things today. I recorded some footage to help convey things a bit more clearly.

 

I inspected my clutch pedal play today and it seems like it might be more than 1/8". I have significantly more pedal play in the clutch pedal than in the brake pedal. Here's a video showing what this looks like: 

 

 

The weird part is that the metal bracket that screws onto the master cylinder pushrod is as far outwards as possible, so it doesn't seem like I can adjust it so that there is less play... The master cylinder that is on the truck is a replacement that I got at O'reilys, wondering if this is what is causing the problem. When I looked at them side by side before replacing it didn't seem like there was much of a difference but who knows. I'm thinking about putting the old master cylinder back on to test this theory (it doesn't seem like there is anything mechanically wrong with it).

 

I also took a video of the clutch slave cylinder movement and the soft rubber line that attaches to the slave cylinder. This is also an aftermarket slave cylinder that I got at O'reilys. The pushrod doesn't seem to be moving far enough and the soft rubber line is not swelling with the clutch pedal depressed:

 

 

Let me know what y'all think or if you'd like some more footage of anything. Thanks for the help!

 

[84seven20]

The clutch pedal does go all the way to the floor and the clutch fluid seems to move through the lines fine so I don't think anything is jammed. Here's some more footage of the clutch pedal movement (you can see the master cylinder arm moving): 

 

[datzenmike]

The master is crap.

[datzenmike]

Factory masters are about $78 so half that is mark up for the dealer. If you paid about $35-$40 then you have a comparable quality master. If you paid $9 you probably have a POS from China. I always take them apart and check for aluminum filings left in the bore and to wet with brake fluid so it doesn't tear up the rubber seal starting up dry.

[84seven20]

44 minutes ago, datzenmike said:

The master is crap.

 

Awesome. At least that's something I can easily replace! I paid $30 or so at O'Reilys for the one that isn't working.

 

I just tested the one that was on the truck originally and it wasn't working. I just took it apart and learned that the reason it wasn't working was because the piston inside the original clutch master cylinder was seized, just broke it free with a few good wacks.

 

I also took apart the aftermarket clutch master cylinder to compare the components. It seems to be comparable by visual inspection but there were definitely some aluminum filings left in the bore. I guess that must have been what was causing the problem. 

 

Do you think it's worth rebuilding the original or should I just buy a new one at this point? I found an OEM Nabco one on ebay for $70. 

 

[84seven20]

Just bought the OEM master and slave cylinders, done messin’ around w/ aftermarket crap. Fingers crossed!