clutch hydraulics
#1
clutch hydraulics
I pieced my car together and for the life of me can't solve my clutch problems. I replaced everything on the clutch (disc, throw out bearing needle bearing, the bearings in the fork, and resurfaced the flywheel). I bled the clutch 3 different ways, pressure bled, used a 200ml mightyvac to force fluid from the bottom, and the method from another member to push the fork in and then pump the fluid.
The problem i experience is that the clutch pedal sticks to the floor. The best results come from pushing the fork in reverse and pumping the pedal, but as soon as i engage a gear and push too deeply on the clutch pedal it doesn't come back unless i coax it back. If i drive for 30 minutes or so, it's weird it's like resistance builds in the pedal, and there are times when it works great, then randomly sinks again.
I have a new master cylinder, new soft/hard line, new slave cylinder and i pressurized via the brake reservoir up to 20psi and no leaks. Anybody have any ideas? I think the slave might have failed internally though it was new (FTE unit). When i press the clutch, i can hear a squeeking noise as the clutch is pressed off the flywheel.
The problem i experience is that the clutch pedal sticks to the floor. The best results come from pushing the fork in reverse and pumping the pedal, but as soon as i engage a gear and push too deeply on the clutch pedal it doesn't come back unless i coax it back. If i drive for 30 minutes or so, it's weird it's like resistance builds in the pedal, and there are times when it works great, then randomly sinks again.
I have a new master cylinder, new soft/hard line, new slave cylinder and i pressurized via the brake reservoir up to 20psi and no leaks. Anybody have any ideas? I think the slave might have failed internally though it was new (FTE unit). When i press the clutch, i can hear a squeeking noise as the clutch is pressed off the flywheel.
#2
Drifting
Did you somehow remove the spring on the pedal? What happens at the inspection window in the bellhousing? Are you certain of the slave rod adjustment?
#3
Nordschleife Master
Clutch pedal to the floor means you still have air in the system. It’s good practice to replace all four components when you open up the system, master, slave, pipe between master & slave and the blue pipe at reservoir.
#4
I did all 4. The problem isn't so much that the pedal sinks, it's that it's not returning of it's own force.
#5
Is it possible it's the bearings that hold the fork and that those don't easily move? The clutch when depressed moves the rod in the slave, but the pedal doesn't readily pop back. I can drive the car if i press the clutch and keep my foot on it and gently the pedal will come back, but not quickly. Something is definitely stuck in the system, just can't figure out what. I don't think it's air per se, unless it's sucking in air somewhere on the return stroke (master/slave cylinders).
Could the seal be blown on one of the cylinders on a new unit?
#6
Race Car
The spring on the pedal (the big blue one) is still there and acts as the cantilever. If i look at the bell housing when i press the pedal, it moves the rod on the slave cylinder. The rod is adjusted to the same length as removal.
Is it possible it's the bearings that hold the fork and that those don't easily move? The clutch when depressed moves the rod in the slave, but the pedal doesn't readily pop back. I can drive the car if i press the clutch and keep my foot on it and gently the pedal will come back, but not quickly. Something is definitely stuck in the system, just can't figure out what. I don't think it's air per se, unless it's sucking in air somewhere on the return stroke (master/slave cylinders).
Could the seal be blown on one of the cylinders on a new unit?
Is it possible it's the bearings that hold the fork and that those don't easily move? The clutch when depressed moves the rod in the slave, but the pedal doesn't readily pop back. I can drive the car if i press the clutch and keep my foot on it and gently the pedal will come back, but not quickly. Something is definitely stuck in the system, just can't figure out what. I don't think it's air per se, unless it's sucking in air somewhere on the return stroke (master/slave cylinders).
Could the seal be blown on one of the cylinders on a new unit?
lay under car with a large flat screwdriver with your body positioned where you are looking at the inspection hole/lever/slave pin.
Place the blade between the fork and the casting and pry the fork opposite it's direction that normally releases the clutch.
Release pressure and allow fork to return slowly.
Repeat several times.
Report back,
T
#7
With Fluid in brake reservoir well past the minimum level that will cover the feed hose to the clutch master, raise pedal by hand to normal height,
lay under car with a large flat screwdriver with your body positioned where you are looking at the inspection hole/lever/slave pin.
Place the blade between the fork and the casting and pry the fork opposite it's direction that normally releases the clutch.
Release pressure and allow fork to return slowly.
Repeat several times.
Report back,
T
lay under car with a large flat screwdriver with your body positioned where you are looking at the inspection hole/lever/slave pin.
Place the blade between the fork and the casting and pry the fork opposite it's direction that normally releases the clutch.
Release pressure and allow fork to return slowly.
Repeat several times.
Report back,
T
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#8
Nordschleife Master
#9
Rod
I have one quick question. Does the piston lay flush with the position of the fork? When I removed the old slave it wasn’t centered, the pushing piston tip was slanted sideways. Did they make clutch forks of different lengths.
#10
Race Car
I have seen one instance where a racer so frustrated with trying to bleed pedal to not load up and go home from a long road trip (Sebring) that he asked me to try the method I described.
It worked for a lap or two but the throw out bearing lock ring was broken on the pressure plate, the resulting vibration would just re-aerate the fluid within 5 minutes.
You have to perform the procedure I described until you don't have any more "swooshing" sound of bubbles/air.
Is your metal tube/rubber hose new....?
I have seen the interior wall of the rubber section peel away internally which caused a one way check valve in the line.
Good luck.
T
#11
Instructor
I had trouble getting mine bled properly when pressurizing the reservoir at 20psi, the tank dipped below the top (blue? can't remember) tube too quickly. Had much better luck with my Motive set at 10psi or so.
#12
No, should line up.
I have seen one instance where a racer so frustrated with trying to bleed pedal to not load up and go home from a long road trip (Sebring) that he asked me to try the method I described.
It worked for a lap or two but the throw out bearing lock ring was broken on the pressure plate, the resulting vibration would just re-aerate the fluid within 5 minutes.
You have to perform the procedure I described until you don't have any more "swooshing" sound of bubbles/air.
Is your metal tube/rubber hose new....?
I have seen the interior wall of the rubber section peel away internally which caused a one way check valve in the line.
Good luck.
T
I have seen one instance where a racer so frustrated with trying to bleed pedal to not load up and go home from a long road trip (Sebring) that he asked me to try the method I described.
It worked for a lap or two but the throw out bearing lock ring was broken on the pressure plate, the resulting vibration would just re-aerate the fluid within 5 minutes.
You have to perform the procedure I described until you don't have any more "swooshing" sound of bubbles/air.
Is your metal tube/rubber hose new....?
I have seen the interior wall of the rubber section peel away internally which caused a one way check valve in the line.
Good luck.
T
That's what originally led me to do the work (soft line), the original was bulged out and i couldn't shift. I think it may be the fork. I pressed in the slave piston a few times, and the swoosh i was referring to was liquid. If i press it back fast and hard with a small prybar, you can only hear liquid. I think the problem is the fork, it's not exactly center on the entire travel path, and as a result it pulls the piston slightly and creates resistance on the way back? I know it sounds like a tinfoil hat idea. The lock ring on the throw out bearing is new, and i don't feel any vibration except when i engage the clutch (the clutch is spring type so there is some vibration in the pedal when i press it in to engage).
The only tell tale sign is a squeaking. After i lift the car, press the piston in like T suggested, there is squeaking, can't figure out if it's the slave, or something else.
I'll bleed again just in case.
#13
Drifting
I didn't get a proper bleed until I used my Motive (at the recommended 15psi) and had my son press the pedal while the system was pressurized and I was cracking the bleed bolt. Only when I did it this way did the pedal fully return.
That fork action does sound funny though. I can't see why a fork wouldn't travel straight? It would have to be loose on its bearings or the pin loose in the bore; either way, you'd have a loose fork, no?
That fork action does sound funny though. I can't see why a fork wouldn't travel straight? It would have to be loose on its bearings or the pin loose in the bore; either way, you'd have a loose fork, no?
#14
Race Car
yes the soft line is new as well. The only thing i didn't change on the entire system is the hard line that goes to the slave (which should be ok since it's metal anyway?)
That's what originally led me to do the work (soft line), the original was bulged out and i couldn't shift. I think it may be the fork. I pressed in the slave piston a few times, and the swoosh i was referring to was liquid. If i press it back fast and hard with a small prybar, you can only hear liquid. I think the problem is the fork, it's not exactly center on the entire travel path, and as a result it pulls the piston slightly and creates resistance on the way back? I know it sounds like a tinfoil hat idea. The lock ring on the throw out bearing is new, and i don't feel any vibration except when i engage the clutch (the clutch is spring type so there is some vibration in the pedal when i press it in to engage).
The only tell tale sign is a squeaking. After i lift the car, press the piston in like T suggested, there is squeaking, can't figure out if it's the slave, or something else.
I'll bleed again just in case.
That's what originally led me to do the work (soft line), the original was bulged out and i couldn't shift. I think it may be the fork. I pressed in the slave piston a few times, and the swoosh i was referring to was liquid. If i press it back fast and hard with a small prybar, you can only hear liquid. I think the problem is the fork, it's not exactly center on the entire travel path, and as a result it pulls the piston slightly and creates resistance on the way back? I know it sounds like a tinfoil hat idea. The lock ring on the throw out bearing is new, and i don't feel any vibration except when i engage the clutch (the clutch is spring type so there is some vibration in the pedal when i press it in to engage).
The only tell tale sign is a squeaking. After i lift the car, press the piston in like T suggested, there is squeaking, can't figure out if it's the slave, or something else.
I'll bleed again just in case.
About every 4-5 times, take the pedal to the top one pump and go back to pumping the 1 inch stroke.
Do that a few times after the stroking of the fork like you already did.
As long as fluid is above the blue feed hose, I can't see you having air in the system.
I have never bled a clutch on a system similar to 944 in the conventional way described here in 25 years.
I have flushed by opening the bleeder, but never touched a bleeder for air in system.
T
#15
I didn't get a proper bleed until I used my Motive (at the recommended 15psi) and had my son press the pedal while the system was pressurized and I was cracking the bleed bolt. Only when I did it this way did the pedal fully return.
That fork action does sound funny though. I can't see why a fork wouldn't travel straight? It would have to be loose on its bearings or the pin loose in the bore; either way, you'd have a loose fork, no?
That fork action does sound funny though. I can't see why a fork wouldn't travel straight? It would have to be loose on its bearings or the pin loose in the bore; either way, you'd have a loose fork, no?