clutch pedal sinks

Sherg86
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clutch pedal sinks

Postby Sherg86 » Tue Apr 07, 2015 6:13 am

Hello,

I'm having an issue in my 87 GTS. It just started happening yesterday. The clutch used to catch all the way at the top, and now it's literally at the bottom, when I lift my foot about an inch or so from the floor, it begins to catch. I checked the fluid level in the reservoir and it's still at the same point, MAX. I looked to see if I can see a leak anywhere, and there's nothing around the reservoir. This leads me to believe that there's potentially air in the line, which would end up needing to be bled. The clutch is fairly new, as is the flywheel, idk if that would have any impact on the situation I have. Similarly, I was sliding around this past weekend and when I finished, there was a whirring noise coming from the rear, still is. I'm lead to believe this is a diff bearing? I don't know, also, would that have any impact on my clutch situation? For the record, I will be upgrading my diff in about a week and while I'm there, I'll change out the diff bearings.

If you guys have any advice or tips, please share! I greatly appreciate it, thank you in advance.

tchybrid
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Re: clutch pedal sinks

Postby tchybrid » Tue Apr 07, 2015 9:35 am

i would definately try bleeding the clutch lines first, possibly air in system. if there is no air, check the travel of the clutch slave cylinder, you may have a faulty clutch slave or even master slave. these parts eventually go out, especially for being 30+ years. I've replaced my fair share of clutch slave cylinders. rear diff noise won't have anything to do with your clutch, just sounds like your r&p may have started to wear out, or the backlash between the gears is starting to increase in spacing.

Sherg86
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Re: clutch pedal sinks

Postby Sherg86 » Tue Apr 07, 2015 10:30 am

Very well, I'll definitely bleed the clutch out immediately. As far as the diff goes, I was gonna upgrade it to the Tomei Trax 2 way anyway so I figure I may as well get that taken care of.

allencr
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Re: clutch pedal sinks

Postby allencr » Tue Apr 07, 2015 9:42 pm

What does 'sinks' mean?
What does the pedal feel like, bit of easy, one finger for the first 1-2cm, then rapid increasing resistance, about 8-10kg, down to the floor? Air is air, squishy, little to no effort to push down on & rapid pumping compresses it and will change the pedal's feel completely.

Cracked/broken clutch fork.
Thanks Morgan!

Sherg86
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Re: clutch pedal sinks

Postby Sherg86 » Wed Apr 08, 2015 4:53 am

I looked at the slave cylinder while i had someone depress the clutch pedal, it moves a good amount, seemingly the proper distance. What i mean by sinks is, there is little pressure in the pedal, and i can effortlessly depress the pedal when driving. It used to catch all teh way at the top, now it's towards the bottom. When i was driving, it would all of a sudden be unable to downshift. If i came to a complete stop, pumped the brake and the clutch a couple times, it would get a little pressure built up, and i'd be able to get moving. Hope that helps, thanks. I'm lead to believe it's the slave cylinder though, no?

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jondee86
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Re: clutch pedal sinks

Postby jondee86 » Wed Apr 08, 2015 4:56 pm

Clutch slave is just a simple piston arrangement with a single seal.
If the seal is leaking fluid will build-up inside the rubber dust cover
until it pops the cover off or leaks out around the edges.

The clutch master is a bit more complicated. First thing to check
would be the pedal height and freeplay adjustment. The pedal top
surface should be approximately 6-3/4" from the metal floor towards
which the pedal travels. Allowing for carpet, say around 6-1/2".

The pedal needs to have between 1/2" to 1" of free play before
resistance from the clutch can be felt. This equates to between
1/16" and 3/16" movement at the actual clutch pushrod. Too much
or too little freeplay will cause clutch engagement problems. So
use the adjustment clevis attached to the clutch master pushrod
to make sure the freeplay is correct.

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.

Sherg86
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Re: clutch pedal sinks

Postby Sherg86 » Thu Apr 09, 2015 4:21 pm

ordered a clutch master and slave cylinder; she'll be up and running tomorrow. 2 way LSD, next week. :)

Sherg86
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Re: clutch pedal sinks

Postby Sherg86 » Fri Apr 10, 2015 2:14 pm

UPDATE***
I bled the clutch and she grabbed perfectly, but shortly after, she started getting air in the system again. I couldn't find any leaks; but i did notice this. The clutch master cylinder cap was slightly moist after i drove her around, so, i was thinking, is it possible that air is seeping into the system there? possibly isn't sealing all the way? I don't know, it's the only logical solution i can think of. Because, correct me if i'm wrong, if there was a bad clutch line, upon depressing the pedal, wouldn't there be a leak somewhere in there? Obviously showing fluid loss? But, the fluid level in the master cylinder remains the same.

Please chime in!!!!

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jondee86
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Re: clutch pedal sinks

Postby jondee86 » Sat Apr 11, 2015 2:14 am

Here is a cutaway drawing of a clutch master cylinder. It is not a very good
drawing, and it is not a Toyota clutch, and it does not show the fluid passageways
to the reservoir. But it does show you more or less what you can expect to find
inside the master cylinder.

Image

When you press the pedal down, the piston moves and the cup washer (seal)
on the piston forces fluid out the end and down to operate the slave cylinder.
If the cup washer is worn or damaged, fluid leaks around the seal and into the
cavity around the piston. The shape of the seal means that it acts as a kind
of one-way valve, so that the fluid behind the piston can easily pass back to
the high pressure side when the clutch pedal is released.

If you get some pedal back by "pumping" the pedal, this is a sure sign that
the seal is leaking. Note that no fluid actually leaks out of the master
cylinder... the leakage is entirely internal.

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.

Sherg86
Club4AG Enthusiast
Posts: 132
Joined: Thu Jan 22, 2015 8:17 pm
Location: Chicago Il

Re: clutch pedal sinks

Postby Sherg86 » Sat Apr 11, 2015 8:56 am

thank you much sir! i greatly appreciate your help

Sherg86
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Posts: 132
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Re: clutch pedal sinks

Postby Sherg86 » Mon Apr 13, 2015 7:04 am

Are there any write ups with pictures on changing the clutch master cylinder? I've tried searching around, and came up with a couple inconclusive ones. I'm gonna tackle this issue around 5:10 PM CST, when I get outta work. If anybody can provide me with a link by then, i'd greatly appreciate it. Cheers.


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