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Old 05-01-2007, 11:39 PM   #1
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clutch engagement point vs clutch pedal play?

After driving a friend's RX-8 (with 35K miles), I noticed that my clutch engagement point is noticeably higher. I also noticed that recently (with wear on my clutch?) the friction "area" itself is taking longer to become full engaged (from the point that the clutch is starting to engage to full engagement).

I dug up the service manual stuff related to clutch pedal adjustment and it specifies the following specs:

clutch pedal stroke: 5.12"
clutch disengagement pedal stroke: 4.402" from the top (.718" from the floor)
clutch free play: .20"-.59" ("until clutch resistance is felt")

I measured my pedal tonight and my measurements are:

clutch pedal stroke: 5.31" (0.19" over spec)
clutch disengagement pedal stroke: 3.875" from the top (0.53" under the spec) (1.4375" from the floor, 0.72" over the spec )
clutch free play: ~1" (about .4" over the spec)

So.. it seems like I'm in a no-win situation here: if I adjust the rod (10mm bolt) to extend towards the clutch pedal (away from the firewall), I will lower the disengagement point, but then I will also increase clutch free play (which is already too much). If I adjust the piston rod the other way (towards the firewall), to reduce the clutch play, I will end up with an even higher engagement point.

That is, if I adjust the piston rod such that the clutch engages .72" from the floor, the I will have increased my free play to 1.72"! That's, like, a lot of free play.

Now, if I adjust the pedal stroke to lower the pedal by .19", then I will reduce my free play by .19". But what will this do to the clutch engagement point? It seems that it would shorten the clutch disengagement "stroke" from the top and keep the stroke from the floor the same. If I then adjust the piston rod to be closer to increase clutch free play back to 1", then I will gain a .19" lower engagement point, just a minor difference.

So am I SOL here or am I confusing something?
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Old 05-02-2007, 02:34 AM   #2
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There is a funny thing about hydraulic clutches (brakes too). The freeplay is never at the slave end of the system. The slave cylinder only retracts as far as the clutch diaphragm pushes it.

The master cylinder end is where the freeplay is, and its really not freeplay at all. The master cylinder just has to retract far enough to uncover an equalization port that lets any extra fluid drain back into the reservoir. This allows the clutch to self-adjust. If you adjust out the freeplay too far, you cover up this port and the system acts funny (doesn't fully engage).

If your clutch suddenly stops disengaging all the way, it usually means that your friction disc has worn down enough that it is beyond the mechanical limits of self-adjustment.

Chances are your clutch is worn out or you have a leak somewhere.
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Old 05-02-2007, 08:14 AM   #3
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Quote:
Originally Posted by Charles R. Hill
Does the clutch fully disengage when the pedal is pushed to the floor? Is it fully engaged when the pedal is released?
Yes, it fully disengages at the floor, and it is fully engaged when it is released. I'm very sure about the first one because I can hear the gears whirring noise stop for about 1.4" of travel. I'm also pretty sure about the second one because there is no clutch slippage and if I rev too high and quickly release the clutch, it quickly clamps down on the RPMs. Is there a better way to check for full engagement?
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Old 05-02-2007, 08:20 AM   #4
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Quote:
Originally Posted by corners
There is a funny thing about hydraulic clutches (brakes too). The freeplay is never at the slave end of the system. The slave cylinder only retracts as far as the clutch diaphragm pushes it.

The master cylinder end is where the freeplay is, and its really not freeplay at all. The master cylinder just has to retract far enough to uncover an equalization port that lets any extra fluid drain back into the reservoir. This allows the clutch to self-adjust. If you adjust out the freeplay too far, you cover up this port and the system acts funny (doesn't fully engage).

If your clutch suddenly stops disengaging all the way, it usually means that your friction disc has worn down enough that it is beyond the mechanical limits of self-adjustment.

Chances are your clutch is worn out or you have a leak somewhere.
Now, in my case, the clutch does disengage all the way, and it seems to be doing it sooner than expected.

How can I check for leaks? The fluid level at the reservoir is about 3/4 way to the max point.

I probably should bleed the clutch, but if there was air in the lines, wouldn't that make it disengage later than usual? (i.e. more pedal effort to disengage)

It seems like I have enough free-play for the self-adjustment mechanism to kick in.

So if my clutch is worn beyond self-adjustment, does that explain a higher disengagement point? and it taking longer to fully engage?

Are there any other checks I can perform?
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Old 05-02-2007, 09:16 AM   #5
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Quote:
Originally Posted by Charles R. Hill
My initial thought is that if it operates properly in all other regards that the clutch is probably fine and the adjustment matter is simply preference. It may take a whole lot of effort to realize a small amount of unimportant difference. How many miles are on your car/clutch?
39K.

I am wondering whether I should try to adjust for a lower disengagement point (and thus more free-play), maybe that will feel OK.
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Old 06-27-2011, 08:38 PM   #6
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My clutch plate broke. I did exactly what syntheticdarkness DIY said to do I had it welded back on and the guy did a good job welding. For some reason when I put my clutch plate back on everything looks normal, but when you push the clutch it goes down about 4 inches and stops. You can easily push the clutch in all the way to the floor and the car will drive fine. But once its pushed down the 4 inches it stays there and doesnt come back up like it used to. The only thing I can think of is maybe the spring got lose somehow? What do you think? I would really appreciate your help with this one!
Also, I just found out that my car will barely go into gear when its not warmed up, but when I let it idle and heat up the gears go right in...HELP!!
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Old 11-18-2011, 10:55 AM   #7
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^ i had this issue on a previous Rx8 i owned and the internals of the transmission ended up fusing together that night. lol
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Old 11-18-2011, 10:55 AM
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