For about a year before I started my project on my car, my clutch pedal had been sticking - in other words, it wouldn't fully return to the released position. I had to pull it back the last inch or so with the top of my foot. I wasn't too worried about it, though, because since I was about to replace every component of the clutch assembly, sure whatever was causing the problem (binding pressure plate spring perhaps?) would go away.
No such luck. After re-installing the slave cylinder (which was replaced a few years ago, along with the master, and the high pressure line), it's doing exactly the same thing as before. So, I did what anybody would do when confronted with a problem with clutch or brakes - I bled the system. Not a single air bubble to be seen, and no affect on the problem, either. The engagement is very smooth, and everything feels fine otherwise, the pedal just doesn't go all the way back to the top.
So, I crawled underneath the drivers side to get a look at the pedal assembly, and watched the action of the assembly as I depressed and released the clutch by hand. Something definitely doesn't look right. The shaft the goes that into the master cylinder through the firewall goes into a pivot bracket (no idea what it's actually called - it looks a little like the turnbuckles used to tension the AC and power steering belts). This is attached to another rod that has a blue coil spring (the boost spring) going around it, and this rod goes through a hole in a metal bracket. Here's a picture of that part of the assembly from the bottom:
[
attachment=10110]
You can see the end of the rod, which has a hole in it which looks like it should have some sort of a pin going through it. It seems that this rod should be secured to the bracket in some fashion, because it's just flopping in the breeze right now, and you can see it move, and then bind up about an inch from the top of the pedal travel, as the clutch pedal is released. Anybody have an recent experience with this part of their pedal assembly? Neither the manual nor the PET show a picture of how this rod is supposed to be attached to the metal bracket. Thanks.
Is there an adjustment procedure for the helper spring that could have something to do with it?
There is an adjustment procedure the sets the length of the rod that is surrounded by the boost spring, and I'll definitely go through the adjustment procedure when I fix the sticking problem, but I think the problem I'm having is because I'm missing some sort of hold-down bolt or pin, because of the way the whole assembly is shuffling around as I release the clutch. It's hard to describe, but the manual has a fairly good diagram of the assembly. If it would help, I could take a picture of the diagram, and include descriptions of what I see moving around when I depress and release the clutch.
Usually if the clutch pedal will not return to the full up position you have air in the system. Did you use a brake bleeder to bleed the system? Have someone work the pedal while you work the bleed screw. Sometimes it can take awhile but it will get there.
Went out and looked at mine. It looks the same as your picture, no pin in that hole, and I don't see it needs one to function. I didn't look close enough, but the pin hole may be needed for adjustment of the spring to hold the rod from turning.
The spring function seems to be to allow the lever mechanism of the clutch pedal to cam over center. So once the pedal is off the floor almost all the way up, the spring will take the mechanism all the rest of the way home after it has cammed over center. I'd definitely adjust this. It will likely fix the issue.
If not, I'd look to worn bushings (item #25 of the parts manual) for the rod (item #4) that the clutch pedal pivots on. Enough sloppiness in this area would allow the toggle feature of the pedal mechanism to not work properly. Sorry, wish I could explain it in better terms.
Okay, gave this some thought. I'd look at mine but I don't think I can get under there without pulling the seat. I think what you are looking for is called the "knife edge bearing." I believe it is a plastic piece of some sort that keeps the rod in line when the spring operates. It looks like you may have one but perhaps it is damaged? I don't think there is anything that goes on the end of the rod when it is through the plate. Perhaps the hole is for a pin to hold it together if you disconnect it from the clutch pedal?
Since you've bled the system I would go with needing adjustment. My clutch pedal was out of adjustment for a while after replacing the master\slave and while I didn't need to actually pull up on the pedal to get it to fully return, it was definitely very dead near full return. It's a pain to get under the dash without taking the seat out, but once I did and finally adjusted it all was back to normal.
I forget exactly what it all looks like under there, but the end from the master that attaches to the pedal is threaded and you can adjust that 1/2 a turn at a time to get the right length. IIRC there's a measurement outlined in the shop manual but I ended up just getting it with trial and error. So lots of disconnecting the pedal and putting it back together :|
Great inputs. I think you're right about the adjustment - there is a procedure described in the manual, and I'll go ahead and check mine, adjust if needed, and see if that fixes the problem. I don't think there's any air in the system. I used the motive bleeder, and there was no air whatsoever in the fluid that it pushed out of the bleed screw. If the adjustment doesn't take care of the problem, I'll take a picture of the picture in the manual, and try to better describe what I'm seeing. In a nutshell, there's a "hitch" in the motion of the pedal assembly - everything moves smoothly, then the whole thing just sort of binds up about an inch from the top of the pedal movement. If I pull on the pedal to unbind it, the whole assembly "hitches" a bit.
I did replace the master and slave cylinder a few years ago, but never checked the pedal adjustment. Hopefully that's all there is to do.
I still vote for air in the system, ha. When I bled my sons 944 I wasn't getting air at the bled screw. I think it migrates up to the master cylinder. Either way, a pain. Let us know!
So, do you feel the binding both on the way up, and the way down after being all the way up? If so, sounds to me like the spring it too tight and goes to shut height (compresses as far as it can, coil on coil) an inch from the top. When you force it past that point, it will free up. The way the mechanism works, move either direction from this point and there is greater distance between the mounting of the spring and the other end that is connected to the clutch pedal.
My clutch pedal will occaisionally do something similar. Every now and then, when I let the clutch out from a stop, it comes most of the way out, then sort of catches and releases the last little bit after my foot is off. I wouldn't know it didn't complete the trip with my foot, except I can hear it kick out the last bit. Doesn't happen on other upshifts (unless I just can't hear it over the engine, etc.).
On my <acronym title='pre purchase inspection'>PPI</acronym> at a local Porsche dealer, the service manager told me my clutch was "loose" and I needed a hydraulic pedal. I didn't understand what he was telling me, as he wasn't talking about the master or slave cylinder or any springs. I had other things that needed fixed sooner, and he didn't think it was urgent, so I didn't worry about it. It doesn't seem to be getting any worse and I haven't investigated any further.
I took a photo of the clutch pedal mechanism in my car (which gave me a chance to fix my squeeky brake pedal...was the brake light switch plunger). My clutch mechanism looks the same, with a hole in the rod. Since you have bled the system, I'd also vote for adjustment of the helper spring which can be seen in the attached photo. I noticed that I get about an inch of movement in the pedal before I feel the hydraulics work, and that helper spring takes care of returning the pedal that extra inch or so. If the spring compression was adjusted too loosely, I imagine the clutch pedal would tend to stop short of a full return as you described.
Well, that was (relatively) easy. I got under there and tried to measure the distance between the firewall and the center of the adjusting rod, as described in the manual. Surely they jest - there's way too much stuff in the way to get a ruler or tape measure between the prescribed measurement points. So I randomly turned the adjusting screw 10 eighth-turns in one direction to see if it made difference. Bingo! The problem is gone - the pedal now return smartly and smoothly to its top position. Unfortunately, I can't say for certain whether I shortened or lengthened the shaft, as I was lying on my back at an inclined angle. I believe I shortened it, but that's just a guess. In any event, it was the "right" direction for my car.
As far as the length of the boost spring (dimension "B" in the diagram in the manual), I can measure it, and it's longer than spec'd - I measure 68.25 mm (2-11/16" on my tape measure), vs. the spec'd 65 mm. Unfortunately, shortening the spring is a pita, as it's difficult to get a wrench on the adjusting screw and move it in the shortening direction due to the stuff in the way. Maybe I'll work with it a little more, or maybe I'll leave it alone, because who knows where I have dimension "A" set to now, and the pedal seems to be working fine now. At least I've identified the knob that controls the pedal-return problem so I know what to tweak if it needs further adjustment.
Thanks for all the great inputs from everybody.
I used a piece of coat hanger wire and marked the distance described in the manual with a piece of tape. You can then place the wire up there and see how close you are to the proper measurement.
Great, glad you solved it! <img src="/forum/images/smilies/968/clap.gif" class="smilie" alt="" /> I learned something new...and also discovered that I am still flexible enough to contort myself into a pretzel under the dash...easy to slip in, trickier to get out!
Eric-
Good idea! I'll give it a try. Only one problem - I used one of our last remaining wire coat hangers to fabricate a hook to fish a section of vacuum hose that I had routed incorrectly through the gaps in the intake manifold...
I went ahead and set the length of the booster spring to 65 mm, as I figured out how to make room to more easily access its tightening nut with a wrench - remove the connectors for the cruise control switch, and press down slightly on the clutch pedal while turning the wrench.
Ha! Mine is suffering ocasionally from the same thing. It just started a couple weeks ago. Thanks for the thread and the advice. I love this forum! <img src="/forum/images/smilies/968/clap.gif" class="smilie" alt="" />
Glad it worked. Figured that had to be the problem. Now I know if I ever have the problem what to do.
And Eric, thanks for the good tip. It's kind of hard to come by wire hangers any more, but some of us old guys have a lot of inventory to work from.
Or a thin wooden dowel should work as well. Great tip either way.
I'm glad the adjusting was the trick you needed. I wish I had Eric's trick of using a coat hanger to do the measurement since I also don't see how you could ever get a ruler or tape measure up there.