280zx clutch disengagement issues

[jon521]

Been awhile since I've posted! Recently I put a 280zx close ratio 5 speed in my 521 (L20b) with a brand new clutch, flywheel, TO bearing/collar, clutch fork, slave, and master cylinder. Ive had it in for about 2 months now and everything was fine. Within the past week I've noticed it was engaging/disengaging lower and lower. So the other day I tossed on anther slave I had, bled about 4-5 reservoirs worth of fluid threw, and it seemed to be better for about 30 mins of driving, but now it's progressively getting worse, now it's hard to put into first gear (sometimes won't) and shifts hard into 2nd. And randomly will work ok but still engages very low on the pedal throw. Fluid level is fine, fluid is clean.

 

I was told it could be an internal leak/bypass, but the master is maybe 3 months old and the slave I put on 2 days ago. I'm stumped, everything has been replaced so that means I either got shitty parts from car quest, or I did something wrong. Any ideas on what it might be?

 

Thanks,

Jon

[Dolomite]

I've had clutch masters go within months before. I have basically the same setup in my 510 and had issues getting it right. I had to mess with it constantly until I found the proper balance between rod adjustment at the master and slave cylinders. It's been best with 280zx master and slave, I don't know if they're any different or if I just got good ones finally. Good luck man, clutch problems are fucking irritating.

[mlw]

Did you get the right throwout bearing collar? - if its a 240mm clutch it needs the longer collar.

The "very low on the pedal" suggests to me its not a fluid issue, but a parts compatibility problem.

I am sure more experienced hands will jump in with more suggestions, but that's where I would look.

Michael

[petercscherer]

"got shitty parts from car quest"

 

I think this might be part of your problem. I recently installed a 1979 280ZX transmission in my 1972 240Z, I initially purchase my clutch slave and master cylinders from Advance Auto Parts, and there were several issues. One, the master cylinder arm wasn't long enough to reach my clutch pedal bracket, and second, the master cylinder was not bleeding out. After talking to the service technicians at ZCarSource and the The ZStore, they recommended that I never buy hydraulic parts from parts stores and instead purchase from reputable Datsun parts suppliers. I purchased new master and slaves cylinders from The ZDepot through eBay and they bolted in perfectly and were bled and ready to go in 5 minutes. I've now put 800 miles on the car since then and I've had no issues at all!

 

What may be your problem is that an air pocket was never fully bled. Another possibility is that either your master cylinder or slave cylinder is too porous and air is leaking into/out of the casting itself; this problem is common with poorly cast products, especially those manufactured in SouthEast Asia. 

 

~Peter

[jon521]

Awesome thanks guys. Currently I'm running 521 master, 620 slave. figured it didn't matter because it's all self-adjusting hydraulic but I definitely could be wrong. I'll look into seeing if I can fit a ZX master on, and getting a good quality ZX slave on there asap.

 

One thing that makes me think it is a hydraulic issue is because I will adjust the pedal so that it releases higher and it works for only for a short period of driving (maybe half a day to a days worth) before it's at the bottom again.

[jon521]

I also considered the wrong TO collar but it released about halfway but for about a month before I noticed it getting lower. Figured if it was mechanical, I would've had problems from the start

[datzenmike]

Lets do a thought experiment.

 

Lets say that the master and slave are working perfectly and pushes 100ml of fluid down the line to the slave. The slave takes this hydraulic fluid and has to push on the clutch arm and move it one inch. This perfectly works the pressure plate.

 

Now you notice lately that the clutch is not disengaging properly and the pedal is going lower and lower to the floor. If you assume that the master is working, then 100ml of fluid is going to the slave. So if it is not moving the full one inch where is the left over fluid going????? Well it can't be compressed and there's no waiting room on the slave where it can go an wait for the pedal to be released. If it isn't squirting out on the ground then you will have to accept that there wasn't 100ml ml fluid coming from the master. Likely fluid is pushing around and behind the seal instead of being pushed to the slave.