Clutch pedal soft at startup

[Read T]

Oh noes.

Well if anyone has been following, my OEM clutch pedal broke so I just replaced it with an RJM. RJM is awesome. I'm hoping I just have things adjusted correctly on the new pedal.

Last night and again this morning, when I went to start the car and the first few times I pressed the pedal, the pedal was very light and there was an excessive amount of free play. After shifting a few times it stiffened up and feels amazeballs. Fluid level hasn't changed when I check it and is at the MAX line.

Can this be anything other than a CSC/CMC. Clutch fluid was replaced with PFC fluid about 2 months ago (and is already black in colour again).

Please say it ain't the CSC. I have to drive to a conference a few hours away this weekend. I shot Ryan an email at RJM.

[wsarver]

For comparison I still have the oem clutch pedal installed and sometimes i have a soft pedal at start up. When I get the fluid nice and hot the pedal gets real stiff and quick. I did a clutch fluid swap 4 or 5 weeks ago so I'm wondering if I have a bubble somewhere in there because my fluid has been at max as well. Sub'd. I bought the RJM I just haven't installed it yet.

[Read T]

^Install it. It's awesome. Maybe I just have a bubble in there that I wasn't able to feel with the OEM pedal.

[Aardwolf]

Please share what Ryan says, I hate to bug the guy. I've experienced the same issue too.

[Read T]

From Ryan, reposted by his permission.

I’m very happy to hear you’re enjoying the new pedal assembly!
The feeling of being softer when you first fire it up cold is an adjustment issue causing the master cylinder not to fully return 100%. This causes the balance port in the MC to stop working so when the car cools off the fluid trapped in the high pressure side of the lines contracts causing the pedal to become squishy almost like air in the lines and then after some driving it warms up causing the fluid to expand again making it feel normal.

There are two main causes for this. The first is a common one where the upper cruise control switch is set too tight or wasn’t adjusted after making a change to the clutch rod or AFP settings during tuning. This holds the pedal arm down stopping the master cylinder rod from fully returning. The upper switch should always be the last item adjusted after any other tuning to prevent this. The upper switch should be adjusted so that the black button is just fully depressed but not so much the rubber bumper is hard up against the metal threaded body of the switch.

The second issue can come from over tightening the two side bolts that lock the up/down movement of the sliding center section. If these are over tightened the main pin bearings will be pinched causing the pedal not to fully return to the top or be sluggish. A quick test for this is to press the pedal down by hand and very slowly let it come up with your hand on top just as if you were letting it up with your foot. Note where it stops on its own and then lift the pedal up a bit by hand to see if it stopped short with some travel left. If you could pull it up more by hand (pedal didn’t come fully up to stop on the upper switch) then go in an loosen the lock nuts on the two side bolts a ¼ turn each and retry the test. Do this as needed until the pedal is returning freely on its own, coming to rest against the upper stop.

Hope that helps and let me know how you make out.

[dashti_370z]

It's normal when you replace your clutch and it will go away after 3 days from installing

[Chuck33079]

Originally Posted by dashti_370z

It's normal when you replace your clutch and it will go away after 3 days from installing

The clutch or the clutch pedal? Because the OP only replaced the clutch pedal.

And it's not normal.

[Spooler]

Need to bleed the clutch system and see if that works. You could have the clutch pedal adjustment off a bit. The stroke may be just bit short.

[dashti_370z]

Sorry , I thought that u replaced the clutch not the padel and I agree with spooler maybe he is right

[SpeedLimit55]

I've experienced this in prior cars and it's due to air in the lines. There is a bleed screw on the slave. Bleed it until you have continuous flow of fluid from this bleed valve.

[Read T]

Adjusted the pedal some more per Ryan at RJM see post #5 and it's doing great now.

FWIW, air in the line could cause a similar problem but I'm pretty sure there wasn't much in there when I bled it last. Using PFC 665 Brake Fluid.

[Read T]

Well, it got softy again this morning before I drove it. Pedal was re-adjusted per Ryan. I'm going to go later this week to have my brake flushed, I guess I'll just have the clutch flushed line.

PS. Normally I would flush everything myself but all my Jackstands are holding up another car, and I have to go to a shop to have a mechanic sign off my tech sheet anyways.

[Rusty]

When you get the system flushed. Break the line open at the master cylinder. You might have an air bubble there.

[Read T]

Originally Posted by Rusty

When you get the system flushed. Break the line open at the master cylinder. You might have an air bubble there.

I haven't really taken a look at the MC much, but do you mean disconnect the line leading from the MC to CSC or disconnect the line from the reservoir to the MC?

[Rusty]

Originally Posted by Read T

I haven't really taken a look at the MC much, but do you mean disconnect the line leading from the MC to CSC or disconnect the line from the reservoir to the MC?

Just crack the line open where the line comes out of the master cylinder to the CSC when you bleed the system. Sometimes a little bubble will hide in that area.