882993md Posted April 12, 2016 Share Posted April 12, 2016 (edited) Hi everyone: I've replaced the bad clutch slave,master cylinder, and a new rubber hose. I used my Motive pressure bleeder to pump 10psi to make sure it will hold and have no leaks before I filled the system to bleed. I came back fifteen minutes later and I see the Motive dropped by about 2 psi. I checked all connections and even used soapy water to detect leaks and found none. I looked at the slave cylinder and noticed that the lever to the pressure plate is all the way to the left and I can't get it to move. Would I need more pressure than my hand can exert to move the pressure plate, or do I have issues with my clutch installation? I can squeeze the fork lever. What is the home position of the fork lever/slave cylinder push rod? Howard 1974 260z Edited April 12, 2016 by 882993md Quote Link to comment Share on other sites More sharing options...
luseboy Posted April 13, 2016 Share Posted April 13, 2016 Did your clutch work before you changed the hydraulic components? Did you keep the master cylinder push rod from your old master? The new masters often come with pushrods that are too short. There are a couple of topics addressing similar poblems that are active currently, and I too am dealing with it (though I believe my problem is the pressure plate/throwout collar combo I'm using). Start by making sure the pedal is adjusted properly(according to the fsm) and go from there. Quote Link to comment Share on other sites More sharing options...
NewZed Posted April 13, 2016 Share Posted April 13, 2016 Here's a picture I took of a working clutch, at rest. On your leak-down problem - there are two seals in the MC; one to build pressure and one to keep fluid in the reservoir (check a later FSM, like 1978, to see a better diagram). I don't think that the MC is meant to hold pressure like a brake MC. It's meant for short time frames. Could be though that you have a leaky one. Quality is poor these days. Did you disassemble and clean it before installing? Did you check the slave dust boot for fluid? Leaks will be contained in the boot. Quote Link to comment Share on other sites More sharing options...
882993md Posted April 13, 2016 Author Share Posted April 13, 2016 (edited) Did your clutch work before you changed the hydraulic components? Did you keep the master cylinder push rod from your old master? The new masters often come with pushrods that are too short. There are a couple of topics addressing similar poblems that are active currently, and I too am dealing with it (though I believe my problem is the pressure plate/throwout collar combo I'm using). Start by making sure the pedal is adjusted properly(according to the fsm) and go from there. My car sat for quite some time before I bought it. The clutch didn't work and I attempted to bleed it. The brake fliud come out looking terrible. I opened the slave cylinder and that's what I saw inside. I ordered a new slave cylinder and figured I might as well swap out the maser cylinder too (the master cylinder actually looked in good shape). I still have the previous master cylinder and I will open up both the old and new and compare the push rod sizes. Howard 1974 260z Edited April 13, 2016 by 882993md Quote Link to comment Share on other sites More sharing options...
882993md Posted April 13, 2016 Author Share Posted April 13, 2016 (edited) Here's a picture I took of a working clutch, at rest. On your leak-down problem - there are two seals in the MC; one to build pressure and one to keep fluid in the reservoir (check a later FSM, like 1978, to see a better diagram). I don't think that the MC is meant to hold pressure like a brake MC. It's meant for short time frames. Could be though that you have a leaky one. Quality is poor these days. Did you disassemble and clean it before installing? Did you check the slave dust boot for fluid? Leaks will be contained in the boot. When I purchased the slave cylinder I took apart and cleaned and rinsed with fresh brake fluid. For the master cylinder I didn't take it apart. I only rinsed it with new fluid. I think I will reinstall the old mc and see if it holds pressure as the rubber seal looks in excellent shape. I will clean it thoroughly. At least I can determine if the new maser is bad. As far as the slave dust boot no dripping fluid inside just slightly wet but that maybe left over from when I cleaned it. I measured just like in your picture and it's about 55 mm from fork arm to the edge of the bolt. but that is with no fuild in the system yet and I still have to adjust the clutch pedal per the FSM. Howard 1974 260z Edited April 13, 2016 by 882993md Quote Link to comment Share on other sites More sharing options...
luseboy Posted April 13, 2016 Share Posted April 13, 2016 When I purchased the slave cylinder I took apart and cleaned and rinsed with fresh brake fluid. For the master cylinder I didn't take it apart. I only rinsed it with new fluid. I think I will reinstall the old mc and see if it holds pressure as the rubber seal looks in excellent shape. I will clean it thoroughly. At least I can determine if the new maser is bad. As far as the slave dust boot no dripping fluid inside just slightly wet but that maybe left over from when I cleaned it. I measured just like in your picture and it's about 55 mm from fork arm to the edge of the bolt. but that is with no fuild in the system yet and I still have to adjust the clutch pedal per the FSM. Howard 1974 260z Do you know the history of the clutch/throwout collar? It's possible that you have the wrong combination, there are two different pressure plates and two different throwout collars, the wrong combination can cause the clutch to not work properly (as it seems to be in my case). Obviously it's much easier to start by addressing the hydraulic components and their adjustments (well, really just the brake pedal adjustment). If the car was sitting for a loong time it's possible that the hard line for the clutch is either clogged or has a hole in it, but you'd probably see brake fluid leaking if it had a hole and you wouldn't get any fluid at the slave if it was clogged. You say there's no brake fluid in there yet? Why not try bleeding it out? This will tell you a lot more. Also, did you install the copper (or brass, not sure) washer that goes between the soft line and the slave? I failed to do this and had a nice puddle of DOT on my garage floor the day after I bled it. Quote Link to comment Share on other sites More sharing options...
NewZed Posted April 13, 2016 Share Posted April 13, 2016 I've replaced the bad clutch slave,master cylinder, and a new rubber hose. I used my Motive pressure bleeder to pump 10psi to make sure it will hold and have no leaks before I filled the system to bleed. I came back fifteen minutes later and I see the Motive dropped by about 2 psi. Seems like you're about to spend a lot of time on a specification that you made up yourself. Quote Link to comment Share on other sites More sharing options...
NewZed Posted April 13, 2016 Share Posted April 13, 2016 Don't forget to consider material relaxation and temperature changes as you try to solve this "problem". You might extend your experiment time out beyond 15 minutes also. See if it levels out or goes to zero. Seriously, it's a good observation, but might not actually be a problem. Quote Link to comment Share on other sites More sharing options...
882993md Posted April 13, 2016 Author Share Posted April 13, 2016 (edited) Don't forget to consider material relaxation and temperature changes as you try to solve this "problem". You might extend your experiment time out beyond 15 minutes also. See if it levels out or goes to zero. Seriously, it's a good observation, but might not actually be a problem. This is my first time dealing with a seperate brake and clutch master cylinder. On combined systems I usually pressure check when lines or components are installed. I'll bleed it after work and hopefully I can move on to other issues like the exhaust. Howard 1974 260z Edited April 13, 2016 by 882993md Quote Link to comment Share on other sites More sharing options...
882993md Posted April 13, 2016 Author Share Posted April 13, 2016 (edited) Do you know the history of the clutch/throwout collar? It's possible that you have the wrong combination, there are two different pressure plates and two different throwout collars, the wrong combination can cause the clutch to not work properly (as it seems to be in my case). Obviously it's much easier to start by addressing the hydraulic components and their adjustments (well, really just the brake pedal adjustment). If the car was sitting for a loong time it's possible that the hard line for the clutch is either clogged or has a hole in it, but you'd probably see brake fluid leaking if it had a hole and you wouldn't get any fluid at the slave if it was clogged. You say there's no brake fluid in there yet? Why not try bleeding it out? This will tell you a lot more. Also, did you install the copper (or brass, not sure) washer that goes between the soft line and the slave? I failed to do this and had a nice puddle of DOT on my garage floor the day after I bled it. When I took a picture of the cruddy old slave cylinder I noticed the copper washer on the old part. I'll need to install it and bleed. Hopefully I won't need to go inside the housing for t.o. bearing or pp issues. The previous owner kept a detailed notebook so I am currently reviewing that for clutch history. Howard 1974 260 Edited April 13, 2016 by 882993md Quote Link to comment Share on other sites More sharing options...
luseboy Posted April 13, 2016 Share Posted April 13, 2016 (edited) When I took a picture of the cruddy old slave cylinder I noticed the copper washer on the old part. I'll need to install it and bleed. Hopefully I won't need to go inside the housing for t.o. bearing or pp issues. The previous owner kept a detailed notebook so I am currently reviewing that for clutch history. Howard 1974 260 No copper washer on the slave is probably why you're losing pressure. I got my clutch to bleed without one but like I said the next morning I had a nice puddle of DOT and no fluid in the resevoir. It's the sealing surface or gasket of the slave cylinder. I also made the mistake of putting pipe thread compound on those threads, which exasperated the problem. You can probably find a new copper washer at a parts store, I know these are also used with brake line banjo fittings which is what I got mine from. Start with the hydraulics, in your original post it wasn't that clear what the problem really was, I didn't realize that you hadn't bled yet. Make sure you bench bleed the master first. I also like to bench bleed the slave, I just clamp it so the pushrod won't fly out and put some fluid through it. Be careful not to squeeze the pushrod while doing this, DOT in the eyes is not fun (ask me how I know). Seriously save yourself the blind walk to the sink and 15 minutes of thorough rinsing and wear safety goggles. Edited April 13, 2016 by luseboy Quote Link to comment Share on other sites More sharing options...
NewZed Posted April 13, 2016 Share Posted April 13, 2016 but that is with no fuild in the system yet and I still have to adjust the clutch pedal per the FSM. I completely overlooked the fact that you pressurized with air. You're just off on a trail of odd actions. Making life complex. Really not much to discuss. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.