85 Nissan 720 4x4 Clutch slave cylinder

[Thomas Perkins]

HI ya'll.I just changed my motor oil a few days ago and noticed that my clutch slave cylinder had some fluid coming out of the rubber boot.I wiped it up and I just went under to see what's happening.Sure enough it is leaking.But I guess it just started cause the reservoir is not low.I changed it back in 2017.I have a warranty,plus I have a new hose that I will put on there.The black outer part is coming apart next to the cylinder.It's been like that for awhile.I just never replaced it.I called the auto part store and they ordered me one.I will take it off after work and take it up there so I can get the new one for free.I have a one man bleeder kit.Also have plenty of brake fluid.Last time it went bad at work.What  I did was,added brake fluid and bled it and got home.It is good to get under your truck often and see what is going on.That is how I found out my rear end oil seal was leaking.

Edited August 3, 2023 by Thomas Perkins

[datzenmike]

Good to get under there. I didn't, but it was winter, and in the spring the differential was totally dry from a leaking seal. Yes the poor differential was baked.

[Thomas Perkins]

I got happy for a second.Got under my truck,no fluid at the clutch cylinder.Then  I pushed the boot in and fluid started waving at me.My part came in and now it's time to get busy.

[Thomas Perkins]

Got her done.Now I am going to put a new fuel filter in.I do it often so I won't get stranded,I do keep a extra in my truck.I also keep a extra fuel pump in there, too,I will also put the little filter in the fuel pump.That brake fluid sure does a number on the clutch master cylinder rubber seal.It cause the brake fluid to turn black.The inside of the clutch master cylinder had black rubber soot in it.When I bled it.I made sure the fluid coming out was yellow when I got finished.Here is the clips I use to crimp the hose coming out of the gas tank.I bought at Walmart in the fishing section.Good for other things.

Edited August 6, 2023 by Thomas Perkins

[datzenmike]

Brake fluid shouldn't hurt rubber,* but being on an engine oil sure will and so will gas and grease. Any hydrocarbon will do this to real rubber. 

 

* I don't think there's much rubber on vehicles today. It's a generic term for synthetic 'rubber' needed for grease seals an such. That should be resistant.

[Thomas Perkins]

The brake master  cylinder new fluid is yellow and in time it also gets dark, does the same thing.It starts out yellow and leaves a black soot in the reservoir when you empty it.You have to bleed it with extra fluid to get all the dark fluid out of it.You need to keep bleeding even after getting all the air bubbles out to have clean yellow fluid in it.I bled it till no air came out.Drove it up the road.Let it cool down.Then Bleed it again.A little air came out and got all the dark fluid out till it came out yellow.The one man bleeder kit is a must have.Set the container higher than the slave cylinder.Air can't go back in.I had it for years.It takes a 5/16 box end wrench for the bleeder valve.My clutch master cylinder was bought when I put the last slave cylinder on in 2017.It also has a lifetime warranty,but it is good.

[Thomas Perkins]

So Clutch slave cylinders go bad cause of the containments in the dark fluid..Causes the seals to leak. Some sites say about brake fluid turning black. Moisture contamination and high temperature.It is good to change the fluid 2 years or when fluid gets dark.I will make a note to change in 2 years.Some sites say it will degrade the rubber seals.So I will be changing my fluid more often.Will make the slave cylinder and master cylinder last longer.But they are free to me,just not the brake fluid.

Edited August 6, 2023 by Thomas Perkins

[datzenmike]

Well seals won't last forever, they wear like everything else. The black is just worn off 'rubber'. If you have a 'rebuilt' or replacement master or slave from China, who knows what they use for the seals. I recently had to replace my slave, didn't have time to look through my parts for one. Naturally I took it apart to make sure there were no machine 'chips' left overs inside and to wet the seal lips so it didn't start dry. The seal was like nothing I had ever seen. This looks like it has cast out of RTV. Very soft like Gummy Bear.

[720_Jeff]

I've noticed, in so many products, 'rubber' like materials, tend to degrade over time.  Newer items, degrade much more quickly than anything I recall from long ago in the past.

Too many products, put this nice comfortable coating on, like gardening tools, plastic, etc.  That stuff turns into a gummy/gooey mess and can be difficult to clean or remove, or at least is in California due to Air Quality board regulations on solvents.

 

I wouldn't be surprised, the seals and other items are formulated differently in modern times and probably degrade much quicker than they did in the past.

[datzenmike]

My ball joint 'rubbers' are soft and like tar.