blew out two clutch slave cylinders in one week

[dazednconfuzd619]

I just bought a nice 1980 datsun 720 4x4 with a stick shift. Great little truck and everything seems to run good except my clutch slave cylinder. When i bought it the guy said it needed a new slave cylinder so i bought one and replaced it. It worked great for about three days the it just gave out all the sudden. I bought another one for a little more cash hoping the first replacement was just a cheap one. Same problem with the second one. Blew out in about three days. It seems like it is just blowing out the rod and little (cant think of what to call it) cylinder or pushing it all the way out. After searching the forums here i read a little about how the master and slave need to be matched but it was a different topic so it didnt really help. I need to figure this out cause i dont want to give this truck up over something so stupid. So if any of you have any suggestions or ideas on how to check things out i would be greatly appreciated. By the way both were brand new parts. First was from Auto parts plus for 13.00 second from napa at 22.00.

[Telkwa]

My guess is there's nothing wrong with the slave cylinder. Something's wrong with the lever it pushes against. Maybe the lever's bent, or the pivot that provides the fulcrum is worn down, or maybe the clutch is completely shot and the lever's traveling further than it should. If the lever's traveling too far, the parts inside the slave cylinder will push right out the end of the cylinder.

I had a similar problem with a brake slave cylinder on an old International dump truck that a guy loaned me. He'd let the brake shoes wear down to almost nothing. A slave cylinder disassembled itself in our front yard. After figuring out how to get the dump truck drum off (hint: car-sized tools will only get you so far) I showed him the parts. He made a new pushrod coming out of the slave cylinder that was longer than the original. The parts stayed inside, I got my job done, and the dump truck was promptly returned before anything else broke.

You could try the same thing for now - cheating with a longer rod - but I would think that you'll want to find out why the lever's traveling so far.

[dazednconfuzd619]

Thanks for the reply. I was really hoping it wasnt anything serious that would cost too much money and time to fix but after finally getting a day off work i had some time to look into it. My first mistake was assuming that because the original slave cylinder was bad when i got the truck and the other two had gone bad that this problem reached back to the first one. Second mistake was expecting the worst and forgetting about the simple stuff. When looking at the transmission and clutch parts i couldnt see anything bent or broken and i started to get frustrated cause i had just bought this truck and didnt want to throw a bunch of money at this truck to figure this out. Then i decided to look at the old slave to see why it had failed. It had just blown a seal not the whole cylinder and i could tell it was probably the original or at least had many of years on it. Then i looked at the rods and noticed that the original was over a half inch longer. I hope i can just use the old rod with a new slave and it will fix it. I am hoping this will fix the problem cause other than this the truck is in good shape and runs great. We will see when i can get to town and get a new slave. Anyways third mistake was trusting a parts store. They never get things right. The best idea is to make sure to bring in the old part to compare to the new one so there is no confusion and they cant try to screw you over on a return. So i will post as soon as i know if it is fixed or not

[Telkwa]

Yeah, it's funny how with the computers and all, they'll still sell you the wrong part as often as not. I'm glad to hear you're making progress. I'm also glad to hear that it probably is not a bent lever or paper-thin clutch.

I've made a few horrific mistakes assuming that the problem was expensive & complicated when it was simple & cheap.

Are you sure the two aftermarket cylinders are not repairable? Oh, wait, maybe they blew open while you were out on the road and the parts scattered? I was thinking that you had everything in your hands but maybe not.

By now the plumbing might have flushed itself out. But you're under the truck anyway so it'd be good to get fresh hyd fluid pumped all the way thru, from master cylinder to the slave. Speaking of which, if you're going to round up the right wrench, a piece of tubing with an appropriate waste fluid jar, and a helper to push on the pedal, maybe you should do the brakes too. I'll bet they'd appreciate new fluid. I don't remember if both systems take the same stuff?