Clutch pedal travels too low - ZR-1 Net Registry Forums

lfalzarano · 03-02-2022

I had a hydraulic clutch failure. So far the master and slave clutch cylinders have been replaced. The clutch, pressure plate and throw out bearing were also replaced.

A road test revealed depressing the clutch pedal barely allowed me to shift into gear. The clutch pedal started to engage about an inch from the firewall.

What could be the source of the low level pedal engagement with the clutch? The re-bleeding of the clutch hydraulics provided no change in the clutch pedal engagement.

Ideas?

Sent from my iPhone using ZR-1 Net Registry

-=Jeff=- · 03-02-2022

what brand/type Master and Slave? are you sure they are good? (even though they are new)

lfalzarano · 03-02-2022

89-1996 clutch master cylinder from Corvette America. It doesn?t say the maker. They listed as their brand.

On the slave cylinder GM parts bought one that was exactly like the one they removed. No idea of the brand.

I suspect either one is letting air into the system. I can?t be the thickness of the rug hindering engagement. The rugs have been around for many years.

Sent from my iPhone using ZR-1 Net Registry

Shizap · 03-02-2022

What clutch disk did you install? If it's not the hydraulics, it could be a matter of needing to shim the pressure plate if the clutch disk is too thick. Marc Haibeck has an article that talks about Centerforce clutch disks and the recommended amount to shim them.

lfalzarano · 03-02-2022

Quote:

Originally Posted by Shizap

What clutch disk did you install? If it's not the hydraulics, it could be a matter of needing to shim the pressure plate if the clutch disk is too thick. Marc Haibeck has an article that talks about Centerforce clutch disks and the recommended amount to shim them.

Thanks for the tip. I have forwarded the article to the service manager at the Chevy dealership.

The clutch kit and clutch slave cylinder was purchased by the the Chevy parts department. I?ve been feeding your suggestions to the service manager. He is in contact with GM support in trying to solve the pedal travel and hard shifting. I also asked Bill at ZFDoc for his thoughts.

Sent from my iPhone using ZR-1 Net Registry

Young1 · 03-02-2022

I have the best luck to reverse bleed the clutch hydraulics to get all the air out of the slave. Ask them if they did that. Simple things first.

Paul Workman · 03-03-2022

Quote:

Originally Posted by Young1

I have the best luck to reverse bleed the clutch hydraulics to get all the air out of the slave. Ask them if they did that. Simple things first.

I'm not familair with the term "reverse bleed". What is that, zackly?

Paul Workman · 03-03-2022

I have bled the clutches on both the Zs by drawing fluid into the system via the slave cylinder -exercising and coordinating the bleeder valve and slave's pushrod to pull in fresh fluid and purge air out of the system. (It's VERY quick and IMO much more efficient than pumping the clutch pedal dozens of times (and I've done it both ways & would never return to the pedal pumping routine...unless I'm on my bicycle!))

-=Jeff=- · 03-03-2022

Quote:

Originally Posted by Paul Workman

I'm not familair with the term "reverse bleed". What is that, zackly?

Pushing fluid up through the slave.. i have a Phoenix Injector for that task

Paul Workman · 03-04-2022

Quote:

Originally Posted by -=Jeff=-

Pushing fluid up through the slave.. i have a Phoenix Injector for that task

Yeah, thanx! And, in conjunction w/ the '91-95 slave (bleeder on the bottom) I see how that tool would really be nice to purge the system.

Got pix?

03-02-2022	#1
lfalzarano Join Date: Feb 2011 Location: Clayton, North Carolina Posts: 1,133	Clutch pedal travels too low I had a hydraulic clutch failure. So far the master and slave clutch cylinders have been replaced. The clutch, pressure plate and throw out bearing were also replaced. A road test revealed depressing the clutch pedal barely allowed me to shift into gear. The clutch pedal started to engage about an inch from the firewall. What could be the source of the low level pedal engagement with the clutch? The re-bleeding of the clutch hydraulics provided no change in the clutch pedal engagement. Ideas? Sent from my iPhone using ZR-1 Net Registry

03-02-2022	#2
-=Jeff=- Join Date: Jul 2007 Location: Bartlett, IL Posts: 7,163	Re: Clutch pedal travels too low what brand/type Master and Slave? are you sure they are good? (even though they are new) __________________ 1990 Corvette ZR-1 #1051 Watson Headers (2" Primary) - Flowmaster Cats - Borla Catback Late Model IH - Plenum Coilovers - 4.10s Shelby Series 1 - Wilwood Brakes Custom Interior NCM Lifetime Member #978

03-02-2022	#3
lfalzarano Join Date: Feb 2011 Location: Clayton, North Carolina Posts: 1,133	Re: Clutch pedal travels too low 89-1996 clutch master cylinder from Corvette America. It doesn?t say the maker. They listed as their brand. On the slave cylinder GM parts bought one that was exactly like the one they removed. No idea of the brand. I suspect either one is letting air into the system. I can?t be the thickness of the rug hindering engagement. The rugs have been around for many years. Sent from my iPhone using ZR-1 Net Registry

03-02-2022	#4
Shizap Join Date: Oct 2020 Location: Coweta, Georgia Posts: 53	Re: Clutch pedal travels too low What clutch disk did you install? If it's not the hydraulics, it could be a matter of needing to shim the pressure plate if the clutch disk is too thick. Marc Haibeck has an article that talks about Centerforce clutch disks and the recommended amount to shim them.

03-02-2022	#6
Young1 Join Date: Sep 2016 Location: Ocala, FL Posts: 901	Re: Clutch pedal travels too low I have the best luck to reverse bleed the clutch hydraulics to get all the air out of the slave. Ask them if they did that. Simple things first. __________________ Steve Young 1991 ZR-1 Quasar Blue Metallic/Black #729 Second Owner 1991 ZR-1 Dark Red Metallic/Black #2040 SOLD 1990 ZR-1 Dark Red Metallic/Saddle #1670 SOLD Double your happiness.....complain half as much.

03-03-2022	#8
Paul Workman Join Date: Nov 2007 Location: Squires (near Ava MO in the Mark Twain N'tl Forest) - Missouri Posts: 6,466	Re: Clutch pedal travels too low I have bled the clutches on both the Zs by drawing fluid into the system via the slave cylinder -exercising and coordinating the bleeder valve and slave's pushrod to pull in fresh fluid and purge air out of the system. (It's VERY quick and IMO much more efficient than pumping the clutch pedal dozens of times (and I've done it both ways & would never return to the pedal pumping routine...unless I'm on my bicycle!))