ZF6 Slave Cylinder Defect Issue FOUND!!!!

[-=Jeff=-]

I got this directly from Bill Boudreau (www.zfdoc.com). As most of you know I have been fighting Clutch Hydraulic Issues for the last month. I went through 5 Masters and 3 slave Cylinders, The Last set being the Aftermarket Cast Units. Now the findings posted regard to the DOM (Drawn Over Mandrel) Cylinders only, Neither Bill or I have disassembled a Cast Slave yet, so we are unsure if they are an issue at this point. If my Hydraulic don’t work for very long with my cast pieces I will take the cast one apart.

So here we go:
It appears that the Seal on the piston in the slave cylinder is installed backwards. One picture below shows the correct and incorrect direction for the Seal. The second picture is a cutaway of the Slave. Bill found this on 2 BRAND NEW Slaves (from GM I believe)

I disassembled 3 Slaves I have. One purchased from The Last Detail in September of 2004, it was in a GM box. One was from Corvette America Purchased in September of 2005. The last one was purchased in May of 2006 from CARQUEST. When I disassembled the Slaves I found ALL 3 to be wrong, the seal was backwards. The GM one I had (From Sept. 2004) also had an external leak which is why I initially changed it, but kept it around for the bleeder and push rod. I contacted Bill with my finding and he will contact a person with GM. So basically this problem goes back to at least September of 2004, maybe before then.

The pictures are from Bill B. I want to thank him for helping me and letting me know what he found. He and I agreed that with my specific problem and the Slave will act as if it was good but is the seal swells it could get stuck in the bore ½ way. I even saw this on the CARQUEST slave that I got. With the Seals corrected that seem to work much better, I know neither leak so I have 2 good parts as spares, assuming the Cast unit works fine.

 

[Mad-Mic]

Jeff glad you found your problem!

thats a bit disheartning that GM Quality for these parts are sub par

 

[-=Jeff=-]

Jeff glad you found your problem!

thats a bit disheartning that GM Quality for these parts are sub par

I own all GM cars, loyal to the GM brand, but I am not surprised by this at all

 

[BlackNBlue95]

Interesting... Good Find..

 

[Mad-Mic]

I own all GM cars, loyal to the GM brand, but I am not surprised by this at all

yeah me too. everything i drive is GM except the fiance's lexus

 

[Edmond]

Only brand loyalty I have is to Martin guitars. Other than that, I get what suits me best. But I do have an affinity towards German guns, I almost refuse to own anything else.

 

[sstearns2]

I have a new slave cylinder that came with my new to me corvette. The one in the car is leaking and I'd like to change it out. How hard is it to disassemble the slave cylinder and fix the seal? Any special tools or anything? Thanks for figuring this out for everyone!

Scott

 

[-=Jeff=-]

not too bad, I fixed the images in my first post so you can see how it is set up.. Hardest part is being sure the edge of the groove for the seal is free from burrs

 

[-=Jeff=-]

Also to add, rumor is the latest slaves have the seal fixed, I am in need of one also for my 90 Z, so I will check it when I get it too

 

[sstearns2]

I just disassembled the one I got with my car. The part was purchased a couple months ago and the seal was installed correctly according to the pictures on ZFdocs website. AC delco part.

A piece of 1 inch PVC pipe works great for reseating the rubber bellows.

Are the seals available anywhere? Is there a rebuilt kit for the slave or master cylinder? I asked the GM parts guy today and he could find anything. It would sure be nice to just be able replace the seal and at the same time know it's assembled correctly.

Scott

 

[-=Jeff=-]

Rebuild kit is avail for the master, not the slave ( at least PNs are shown for master)

 

[G Winter]

I purchased a Wagner slave at the local parts supply late last summer for $106 , works great.
Measure the bore with a calipers and take the seal to your parts supplier , they may have an assortment that you could match it .

Glenn

 

[sstearns2]

Hopefully the wagner is better. I just disassembled my AC delco slave cylinder for the second time to check for burs. The edge of the groove looked good, but then I used a long Qtip to clean out the bore and found three metal shavings down at the bottom of the bore. These would have destoryed the seal over time I'm sure.

I personally would not install a new slave cylinder without disassembling it first to check the seal and clean out the bore. I can do it in about 3 minutes now that I've done it twice. Harbor Freight has cheap clip ring pliars for about $6 right now. A little compressed air pops the piston right out. A piece of 1" PVC pops the rubber bellows into place. I also went in with a small screwdriver and made sure each of the little ears was seated. There's no way to tell if it was disassembled.

I'm getting a new master cylinder too. I'm planning on disassembling that too.

My local chevy dealer's website show a rebuild kit for the slave and master cylinder. I haven't talked to the parts guy to see if you can actually get them yet. The slave kit is only about $20, so it may just be the seal.

I'm starting to remember why my daily driver is a honda product.

Scott

 

[G Winter]

No problems with the Wagner. I did fill it and pump it to remove the fluid twice. Then I filled it and attached the new line before installing it. This made the bleed process a little easier.

Glenn