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Old 08-06-2013, 05:35 AM
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Hydraulic Clutch pros-come on in.....

Been driving the car with no issues for a couple of months, last night took it to cruise night. About 1/2 way to my destination, approx. 6 miles came to a stop light, when the light turned green, the clutch pedal stayed on the floor!
Had to pull it back up with my hand. Never had this issue before, everything is brand new-clutch, disc, pressure plate, hydraulic throw-out bearing etc.
Limped home, and checked fluid level in the clutch master cylinder and was fine. Crystal clear fluid also. Didnt see any leaks in the lines either.
Any ideas why all of a sudden this happened?
Only thing I've done from the first install was lengthened the push rod (into the master) in order to get the clutch pedal high enough to match the brake pedal. Could this "lengthening" of the push rod cause this? Maybe the "stroke" is too long?
The clutch actually works very well, but I only need to push the pedal down an inch or so. If I go to the floor with it, it sticks there. Nothing in the path of the push-rod linkage or the pedal arm.....
Signed:
Confused.....

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Old 08-06-2013, 05:41 AM
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Sounds to me like it's traveling past it's optimal stroke length. Maybe move the rod up further on the clutch pedal or put a stop on it so that you don't push it too far.
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Old 08-06-2013, 05:52 AM
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Quote:
Originally Posted by Greg T View Post
Sounds to me like it's traveling past it's optimal stroke length. Maybe move the rod up further on the clutch pedal or put a stop on it so that you don't push it too far.
Hi Greg....my thoughts are the same, but I would think it would have done it from the start? Been drving it with no issues for weeks....
Maybe I just have to have that pedal lower than the brake so the "stroke" isnt as long....
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Old 08-06-2013, 06:13 AM
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I just read an article that said if the slave cylinder(in my case the throw out bearing) can get hot from engine heat and cause the piston to heat up and expand which causes it to stick and thusly prevents the pedal from returning???
If this is the case, maybe a simple return spring somewhere on the pedal assembly could solve this issue???
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Old 08-06-2013, 06:47 AM
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Perhaps a heat shield to prevent that issue, instead of a spring trying to force it to work. As some point, if that keeps happening, you'll probably damage one of the seals in the unit. Its reasons like this I don't like HYD clutches for most applications, bt in a street rod like yours, there often isn't any alternative
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Old 08-06-2013, 07:19 AM
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Yes, I agreed about a heat shield, but not sure where this can be placed.....since T/O bearing is on tranny shaft.....
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Old 08-06-2013, 09:28 AM
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this is what I get for not having the proper level of high octane coffee. For some reason I thought just put a shield around the master. What brand of hyd clutch are you using?

I just had a race customer that bought a "Howe" kit I believe and it needed so much free travel it practically fell off the input bearing retainer (the cast iron flange that bolts on the front). He had to exchange his for a T5 style one from the same company, which has a much narrow body and doesn't hog as much room.

Post your installation procedure sequence, and how you adjusted it. Sometimes we over think it and and writing out the steps will shed some light on it.
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Old 08-06-2013, 09:37 AM
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LOL....that was back in March, and I cant remember what I had for dinner last night!
I will check my records when I get out of work. The clutch master is mounted under the floor with no heat source anywhere near it. Pretty sure its a RAM clutch it (plate & disc), with a RAM hydraulic throw-out bearing:
http://www.summitracing.com/parts/ram-78125
pretty much gets installed onto tranny shaft using shims, I used dial calipers to install at proper dimensions per instructions. Oh, BTW, I measured EIGHT times! LOL
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Old 08-06-2013, 10:13 AM
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What type of pressure plate is the clutch cover? A diaphragm type spring can go "over center", and the "fully down" pressure is actually a lot less than than the pressure when the clutch is engaged.
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Old 08-06-2013, 10:51 AM
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Not sure what your saying, but the pressure plate IS diaphram style....
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Old 08-06-2013, 02:00 PM
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If you press a diaphragm spring too far, it gets soft.

A normal spring, more travel, more load. Example, lets say you take a spring, compress it 1 inch, and it has 100 pounds of load, or push. 2 inches, 200 pounds, 3 inches, 300 pounds.

A diaphragm spring is not like that. If you had a diaphragm spring that had the same travel as the spring above, 1 inch may be 100 pounds, 2 inches may be 125 pounds, and 3 inches could be 50 pounds.

A diaphragm spring is used in clutches because properly set up, the pedal pressure is pretty light, with the clutch pedal on the floor, but as the pedal comes up, the clamping force on the clutch disk actually gets heavier, and ideally, the clamping pressure is at the highest when the clutch is fully engaged.

You say it worked OK before you lengthened the master cylinder push rod? With the push rod lengthened to raise the clutch pedal, you now make the slave cylinder move too far.
Did the master cylinder, and the slave cylinder come as a matched set? Possibly getting a smaller diameter master cylinder would help. Smaller diameter, less fluid movement, but also lighter pedal pressure.

Last edited by DanielC; 08-06-2013 at 02:05 PM.
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Old 08-06-2013, 02:59 PM
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Great Googly Moogly......that's way too much info for my feeble brain...LOL
What I did mean, I lengthened the shaft at installation, so it has always been that length, and for the first few weeks, worked perfectly fine. Only difference now is the hot weather, not sure if that matters.....
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Old 08-06-2013, 05:01 PM
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The problem is heat swelling the piston in the master as was mentioned. Mae a heat shield for it. You can also make an air duct and pipe in cooleer air around it. Use some kind of convoluted flex hose, similar to a heat riser tube on the older cars. Or dreate a deflector to bring it in.
Old Toyota land cruisers had a pancake flat type of fan that was hooked to atube that blew outside(not underhood) air on all the fuel injectors during some engine operation conditions and after each shut down to keep them alive as the heat was doing some bad things to the.
Its the same principle.
Heat kills. Keep it off your goods, they will live longer.
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Old 08-06-2013, 07:20 PM
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Quote:
Originally Posted by LATECH View Post
The problem is heat swelling the piston in the master as was mentioned. Mae a heat shield for it. You can also make an air duct and pipe in cooleer air around it. Use some kind of convoluted flex hose, similar to a heat riser tube on the older cars. Or dreate a deflector to bring it in.
Old Toyota land cruisers had a pancake flat type of fan that was hooked to atube that blew outside(not underhood) air on all the fuel injectors during some engine operation conditions and after each shut down to keep them alive as the heat was doing some bad things to the.
Its the same principle.
Heat kills. Keep it off your goods, they will live longer.
I don't think its heat at the master, there's nothing hot near it? Its located on the frame rail under the floor pan, with lots of fresh air hitting it? There is no exhaust under the car either......
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Old 08-06-2013, 07:51 PM
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Too much stroke

Adjust it back where the clutch pedal is lower. Done deal. One inch of travel to disengage the clutch is not the way its supposed to work. You're either jamming the hydraulics from too much stroke or over throwing the clutch release forks. Nolan
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