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Hydraulic clutch bleeding

Sketchysedan

New member
Joined
Feb 20, 2019
Just installed a spec stage 3 clutch in my 740 turbo. I?m using a new clutch, new clutch fork and new slave cylinder with a flat flywheel. When using the factory rod on the slave cylinder, after bleeding, the piston over extended and the seal blew out of the slave. I made a longer rod and bled the clutch again, and it seems to hold pressure. The only issue is that the clutch grabs all the way at the top of the pedal throw and slips in anything but first gear. The clutch feels firm and I am getting clean fluid and no air when I open the bleeder. What should I do next? There is not much tension on the clutch fork with no pressure on the pedal, I don?t understand why it is slipping.
 
New rod too long? Is there any free play or is the rod/arm tight in the slave cylinder?
 
You need to adjust the pivot point of your clutch fork. Is this with a stock M46 car? Could be that the stack height of the pressure plate fingers is lower than stock.

Yay 80/20 aftermarket parts!
 
no, it was a factory b230f/aw70 that now has an ft and m46. How do I adjust the pivot point of the clutch fork? I was having the same issue when I had the stock clutch installed, but assumed it was because the clutch fork I was using was cracked and worn on the pivot. I replaced the clutch fork and slave and same thing is happening. There is no play between the clutch fork and slave cylinder- I used a section of threaded rod and two jam nuts to make an adjustable rod. If I make it shorter, the piston pushes out of the slave. Any adjustment I make has no effect on clutch feel- there is always the same tension on the clutch fork, the only thing that changes is the ?neutral? position of the piston. This is why I am confused on how to adjust it.
 
Is the Spec clutch listed as applicable to the flywheel you are using? Has the flywheel been resurfaced? You definitely have a stack height issue, which moving the pivot point would compensate for. Extending the rod is not the solution as you have found. If you try driving the car & shift w/o the clutch mechanism (just rev-match), and it slips under load, you definitely have an overall problem with the clutch/flywheel setup.

Spec is really iffy in terms of quality/consistency. I have used a range of stage III setups (on whiteblocks) with sprung, unsprung discs, and never found them to be satifactory under all driving conditions.
 
Stage 3 being a ceramic puck clutch?
If so, those don't have a lot of modulation to them. More on/off, with squealing in between those if you slip them a lot.

If it's slipping:
Did you clean everything with brake clean before assembly?
Is the FW resurfaced?
 
You need to adjust the pivot point of your clutch fork. Is this with a stock M46 car? Could be that the stack height of the pressure plate fingers is lower than stock.

Yay 80/20 aftermarket parts!
Yes, or if it is too high the belleville spring goes over-center, so to speak, and the clamping force is weak.

no, it was a factory b230f/aw70 that now has an ft and m46. How do I adjust the pivot point of the clutch fork? I was having the same issue when I had the stock clutch installed, but assumed it was because the clutch fork I was using was cracked and worn on the pivot. I replaced the clutch fork and slave and same thing is happening. There is no play between the clutch fork and slave cylinder- I used a section of threaded rod and two jam nuts to make an adjustable rod. If I make it shorter, the piston pushes out of the slave. Any adjustment I make has no effect on clutch feel- there is always the same tension on the clutch fork, the only thing that changes is the “neutral” position of the piston. This is why I am confused on how to adjust it.
The arm being cracked only matters for disengauging. The cover (pressure plate) is what clamps, and is best at the spec height. If the disc is too thin or too thick, no clampy. oil on surface, slips no matter how much clamping. Etc.
You had an issue before, of course it is still there.
 
Is the Spec clutch listed as applicable to the flywheel you are using? Has the flywheel been resurfaced? You definitely have a stack height issue, which moving the pivot point would compensate for. Extending the rod is not the solution as you have found. If you try driving the car & shift w/o the clutch mechanism (just rev-match), and it slips under load, you definitely have an overall problem with the clutch/flywheel setup.

Spec is really iffy in terms of quality/consistency. I have used a range of stage III setups (on whiteblocks) with sprung, unsprung discs, and never found them to be satifactory under all driving conditions.
What you are calling "stack height"..do you mean the disc thickness? Or are you referring to something else?
 
Yes, the clutch is matched to the flywheel. Flywheel was freshly machined and everything was clean. The spec stage 2 in my 240 turbo performs great. I will see if it slips without pressure on the fork tonight. Since I am using a flat flywheel instead of a dog dish, do I need to move the pivot ball towards the front of the car and extend it?
 
What you are calling "stack height"..do you mean the disc thickness? Or are you referring to something else?

Flywheel, Disc & PP. They need to be matched as a set. as I'm sure you are aware, any clutch kit for a specific application is designed to operate in a very narrow window - if the throw is - + what that is designed for, it won't work as intended, whether it be pedal position, over extension of the slave, PP fingers damaged, etc....
 
Flywheel, Disc & PP. They need to be matched as a set. as I'm sure you are aware, any clutch kit for a specific application is designed to operate in a very narrow window - if the throw is - + what that is designed for, it won't work as intended, whether it be pedal position, over extension of the slave, PP fingers damaged, etc....

+1

In my case with Redblock hydraulic clutches, I like to have the fork positioned so that the pushrod is close to bottomed out at resting position.
 
Anyone know if it is possibly to get the clutch fork and pivot ball out without pulling the trans again?
 
Flywheel, Disc & PP. They need to be matched as a set. as I'm sure you are aware, any clutch kit for a specific application is designed to operate in a very narrow window - if the throw is - + what that is designed for, it won't work as intended, whether it be pedal position, over extension of the slave, PP fingers damaged, etc....

Never heard it called that, just step height. Stack reminds me of a bike headset. Thanks.
 
Doesn’t the slave cylinder piston overextending point to a different issue? Just asking because that also happened in my 122 with a Spec stage 3 clutch, factory 122 master, and 740 slave. I just assumed the two weren’t matched perfectly and was going to rig up a pedal stop to keep the slave from pushing the fork too far. Otherwise the clutch operates perfectly.
 
Yes. That points to a pushrod or pivot issue.

I looked up clutch stack height. It pertains to automatics and motorcycles. I knew it rang a bell aside from steering head sets.
It does not pertain here.

Usually you have a step height (+-) for a clutch and cover pair. Mix and match means you need to measure the FINGER height with spec disc, then new disc, then add/subtract the step height.
 
Ok guys. Just used two washers to space out the pivot ball. I can now use the factory rod included with the master cylinder, the piston is almost bottomed out in the cylinder when the fork is in its neutral position. However, the clutch still grabs all the way at the top of the pedal throw and the clutch still slips. What next? I?m still not understanding why it grabs so high up on the pedal throw.
 
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