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Clutch Hydraulics repair - pedal to the floor - 2005 Enthusiast
Back on 23-Aug, I was on my drive home from work when, on shifting, the clutch pedal went all the way to the floor and stuck there. I was able to use rev-matching to shift the rest of the drive home. And then a wasp sting on 24-Aug landed me in ICU for 5 days (2.5 days on a ventilator), so I got a little a side tracked
I have searched the forums, and the preponderance of evidence leads me to think that it is most likely a failed clutch slave cylinder. The slave cylinder sits out in the elements, and my Z was driven year-round by the previous owner, so its failure makes the most sense. The date-code on the flex line to the slave cylinder shows that at least that line is original (07-2004). I did check that the clutch fork was not loose, so it is not a failed pivot ball. I do have that pivot on my list of upgrades to tackle whenever a repair arises where the transmission would have to be removed, though.
So, if I'm going to replace the clutch slave cylinder, then I figured I'll also replace the flex hose connecting to it, and the lower hard line from the junction in the wheel well to the flex line. I'm also ordering a new bango bolt, gaskets, and the clip for the joint between the hard line and flex line.
I'll update with the post-repair/post-bleed results.
I had an E21 BMW 320i years ago, and the clutch slave cylinder would fail on that every couple of years. It was almost like clockwork, as it would fail with the first real cold morning of the year, and as I pushed in the clutch pedal to start the car.
The Z has 127k miles on it now and will remain as my Summer driving car.
Back on 23-Aug, I was on my drive home from work when, on shifting, the clutch pedal went all the way to the floor and stuck there. I was able to use rev-matching to shift the rest of the drive home. And then a wasp sting on 24-Aug landed me in ICU for 5 days (2.5 days on a ventilator), so I got a little a side tracked
I have searched the forums, and the preponderance of evidence leads me to think that it is most likely a failed clutch slave cylinder. The slave cylinder sits out in the elements, and my Z was driven year-round by the previous owner, so its failure makes the most sense. The date-code on the flex line to the slave cylinder shows that at least that line is original (07-2004). I did check that the clutch fork was not loose, so it is not a failed pivot ball. I do have that pivot on my list of upgrades to tackle whenever a repair arises where the transmission would have to be removed, though.
So, if I'm going to replace the clutch slave cylinder, then I figured I'll also replace the flex hose connecting to it, and the lower hard line from the junction in the wheel well to the flex line. I'm also ordering a new bango bolt, gaskets, and the clip for the joint between the hard line and flex line.
I'll update with the post-repair/post-bleed results.
I had an E21 BMW 320i years ago, and the clutch slave cylinder would fail on that every couple of years. It was almost like clockwork, as it would fail with the first real cold morning of the year, and as I pushed in the clutch pedal to start the car.
The Z has 127k miles on it now and will remain as my Summer driving car.
Good troubleshoot and while you're at it, may want to check the master cylinder (and change as needed) as well. Not that expensive and since the system is going to be open, do it all at one time. Tip: Use a power bleeder, e.g., Motive.
Good troubleshoot and while you're at it, may want to check the master cylinder (and change as needed) as well. Not that expensive and since the system is going to be open, do it all at one time. Tip: Use a power bleeder, e.g., Motive.
I really did think about just doing the whole system now. But, the ease of accessibility to the Master Cylinder and that upper hardline (actually, the whole of the system from the pedal to the clutch fork is pretty accessible) let me decide to just replace the slave cylinder and the related lines/joints that were the most corroded, for now.
As for the bleeding, I intend to visit a junkyard (well, I won't...at least not until the first good frost around here) and source a spare clutch reservoir cap, and then convert it to my Bleeder Buddy-style application. I sold a CNC-milled version of the ubiquitous ATE/Teves brake fluid reservoir cap with a 1/4 NPT air fitting on it for some years in VW, BMW, Mercedes, Porsche, etc. forums. I created it so that my wife wouldn't have to come out to the garage to help me bleed the brakes. Wow, I searched back...the first of these I put together before 2002.
I really did think about just doing the whole system now. But, the ease of accessibility to the Master Cylinder and that upper hardline (actually, the whole of the system from the pedal to the clutch fork is pretty accessible) let me decide to just replace the slave cylinder and the related lines/joints that were the most corroded, for now.
As for the bleeding, I intend to visit a junkyard (well, I won't...at least not until the first good frost around here) and source a spare clutch reservoir cap, and then convert it to my Bleeder Buddy-style application. I sold a CNC-milled version of the ubiquitous ATE/Teves brake fluid reservoir cap with a 1/4 NPT air fitting on it for some years in VW, BMW, Mercedes, Porsche, etc. forums. I created it so that my wife wouldn't have to come out to the garage to help me bleed the brakes. Wow, I serarched back...the first of these I put together before 2002.
Very cool. Apparently I'm preaching to the choir. Laff....
If you're going to replace any of the clutch lines, you can replace both the hardline from the CMC and the insulated line under the car with a single long SS line. I know ISR makes one for the DE (but not the HR).
I'm doing an entire clutch system refresh on my HR, OEM CSC, Zspeed heavyduty CSC, Luk clutch/flywheel, and Zspeed's SS lines to replace the hardline and the insulated rubber line under the car.
If you're going to replace any of the clutch lines, you can replace both the hardline from the CMC and the insulated line under the car with a single long SS line. I know ISR makes one for the DE (but not the HR).
I considered going that route (replacement SS line), but for now I'm just going to replace the failed slave cylinder, and then I figured I'd also replace the items that are badly corroded that could present a problem during removal/installation. The lines/components from behind the inner fender liner in the wheel wheel up through the master cylinder are still relatively clean/un-scathed.
Also, the OEM flex line to the slave cylinder on my Enthusiast did not have a thermal wrap.
I considered going that route 9replacement SS line), but for now I'm just going to replace the failed slave cylinder, and then I figured I'd also replace the items that are badly corroded that could present a problem during removal/installation. The lines/components from behind the inner fender liner in the wheel wheel up through the master cylinder are still relatively clean/un-scathed.
Also, the OEM flex line to the slave cylinder on my Enthusiast did not have a thermal wrap.
Fair enough.
I've just read/been told by several people that bleeding the clutch system is more difficult than it should be due to the loop that the hardline has behind the fenderliner, so I wanted to remove that annoyance.
I know my 08 has an insulated stubby line under the car, and I can't remember if my 04 did or not. I did have a non-insulated SS line to go in my 04, though.
Most of the time this is actually a failed MASTER. Sediment from the line builds up in the master and causes the piston to stick. Simple thing to do, replace or rebuild both when you do it.
Most of the time this is actually a failed MASTER. Sediment from the line builds up in the master and causes the piston to stick. Simple thing to do, replace or rebuild both when you do it.
Fair enough. While I'm waiting for the parts to come in, I can have a look at the Master cylinder, too - access is easy enough in the vehicle. And, it would explain why I haven't lost anymore fluid since topping off the reservoir (if the master cylinder piston is stuck in the engaged position), despite having cycled the clutch pedal.
So, there is not physical connection between the clutch pedal and the master cylinder piston? It is just a rod that presses on the piston, and then returns with pressure from a return spring? Is there a cutaway view somewhere?
So all the parts came in (it took a lot longer than I thought - almost 3 weeks) and I finally got around to replacing everything this weekend. I installed the Clutch Master Cylinder rebuild kit, the new Clutch Slave Cylinder, new Flex Line (the new one was insulated...maybe my original one was, too, and the insulation degraded off over the years?), and new Lower Clutch Line (from behind the fender liner to the Flex Line). This was also done with a new Banjo Bolt and gaskets, and a new clip to secure the end of the Flex Line.
Long story short, after a couple attempts at pressure bleeding, I still do not have resistence when I press the Clutch Pedal. It goes down to the floor, and I have to pull it back up. Cycling the pedal a few times does not build up pressure, either. There is no sign of fluid leaving the system anywhere, either (the fluid level does not drop). I should add that using my pressure bleeding setup, I did have fluid flowing at the bleeder valve on the CSC. I never really saw a bunch of air bubbles leave through there, though.
I did bench bleed the Clutch Master Cylinder before installing it - it pushed out fluid without trouble. The bore of the CMC was clean and free of scratches or grooves, too. I also wedged a prybar onto the Clutch Fork and got the expected resistance from trying to disengage the Clutch.
After the power bleeding attempt, I went back and re-read the threads I could find on bleeding the clutch, read the procedure in the FSM, and then tried again. Mostly, I followed the instructions from this post: https://my350z.com/forum/maintenance...ml#post9842525
I'm still not sure it's doing what it needs to - I'll add more pictures and detail in the next post.
I'm open to ideas for what else to try...
The new piston assembly is on the left...the spring was an 1/8" or so longer than the old one. The old one likely compressed a little over the 125k miles that were on it.
I'm not sure if the Clutch Master Cylinder failed (it was dirty in there), or if there was a pinhole or weak point at the joint between the old lower hard line and the flex line. The old flex line broke off pretty easy.
I used one of the old plastic versions of my BLeeder Buddy, and notched it to allow for it to fit over the Clutch Fluid Reservoir.
Here is how the modified Bleeder Buddy sits on the Clutch Fluid Reservoir. I dialed in a little pressure and just held it down in place to push the fluid through.
With myself under the car and the bleed screw and my daughter doing the clutch pedal pushing/release duty, we did get a little better reaction from the pedal, but it still doesn't seem right for a few reasons: 1) even after the additional bleeding, the pedal travels all the way to the floor, 2) the pedal does not return to the same height as the brake pedal when released (it sits a couple inches lower, and it is beneath the "hitch" in the travel path where the clutch pedal return spring would bring it all the way back to the top of its possible travel), and 3) when under the car, with the pedal depressed the clutch fork only seems to be moving about 1/2inch.
The pedal is no longer sitting all the way on the floor when released, so I think that is a change from before I made the repairs. But it just doesn't seem like the pedal is coming up far enough. And then, I don't know that the clutch fork is moving far enough from the pressure of the CMC and CSC.
I haven't tried the Z out on the road, yet, as I want to be sure everything is working as it should and not inadvertently cause wear or damage to the clutch or driveline.
Also, I did double-check the position of the clevis pin from the CMC rod fork to the pedal. This was to makes sure, per the FSM, that the pin fit loosely in the pedal, and was not being pulled or pushed against it. The clevis pin has freeplay when the clutch pedal is at the top of its possible travel.
Some more pictures, then: Clutch pedal at the top of its travel, pulled all the way up past the "hitch" in its travel where the return spring activates and pushes the pedal all the way up.
This is the resting position of the clutch pedal after the bleeding. It seems low (a couple inches below the brake pedal height) - this seems wrong. This is how the return spring looks with the clutch pedal all the way up. This is how the return spring looks with the clutch pedal in post-bleed resting position - the pedal seems low.
I did take the Z out for a short drive up and down the street. With the pedal resting that low, the clutch pedal travel seems extremely short. But functionally, when I press in the clutch pedal (clutch dis-engaged), there is no grabbing or creep - so the clutch seems to be fully dis-engaged when the clutch pedal is fully pressed. I'm still not comfortable risking stop and go traffic to work, yet, until I get some feedback on whether this is normal.
My frame of reference for this car is pretty limited, as I first started driving it this Summer and have only put about 2500 miles on it before the clutch line went out.
Most of the time this is actually a failed MASTER. Sediment from the line builds up in the master and causes the piston to stick. Simple thing to do, replace or rebuild both when you do it.
I did clean the CMC and install the rebuild kit with the new piston and seals.
As for the Tilton or Wilwood CMC upgrade, that is likely something I will do in the future. I also had a look at the RJM Rev.4 adjustable clutch pedal assembly, and I like the looks of that for a future upgrade, too. I saw that both of these paths were recommended as good upgrades in the other threads on clutch hydraulics and bleeding I researched.
For now, I'm trying to understand if the way my pedal is sitting in its resting position is normal behavior for the OEM setup? Or, is it a sign that the clutch friction surface is getting low (and the pedal is resting lower as a result)? Or something else? I don't have enough seat time in the Z to make that judgement. Now, if it was a VW, I'd have plenty of experience to draw from there
So this afternoon I went and looked at a work colleague's 2003 250Z that has a stock clutch setup (he also has a nicely-done supercharger kit installed with a conservative tune). Based on that comparison, my clutch pedal's resting position is not correct.
Another data point, while lying under the Z and bleeding the clutch at the slave cylinder, I was able to move the clutch fork back another inch or so (towards the front of the car) from the resting position, further compressing the clutch slave cylinder piston. I'm not sure if that is normal or not, and I didn't get chance (and his car doesn't have the clearance, as it is lowered) to check on my colleague's Z.
And tonight's update...I put the Z up on ramps and had another look underneath. When the pedal was in the new (low) resting position, there was no freeplay on the clutch fork. I raised the clutch pedal all the way up, and there was room to move the clutch fork again. Pressing and releasing the clutch resulted in the same behavior since the repair and bleed - the pedal sits low to the floor and there is very little travel.
I pulled the pedal all the way up and went and ran some errands in town for a couple of hours. When I came home again, I tried the clutch again, and this time the pedal would return all the way to the top of its travel. The "hitch" in the travel from the return/assist spring is noticeable at the top of the pedal travel, but it at least is coming up all the way on its own.
Earlier in the day, I was worried that perhaps the clutch pivot bolt had broken, but that does not seem to be the case. The clutch fork does not wiggle in or out or up or down, just back and forth along the travel path. So, I'm wondering if I still have an incomplete bleed somehow. I'll leave it sit overnight like this and see how things feel in the morning again.
09-04-2019, 04:56 AM
Clutch Hydraulics repair - pedal to the floor - 2005 Enthusiast
