Line lock question

tommy d · 05-10-2015, 07:32 PM

Speaking of line-locks. Has anyone ever had a spongy pedal because of a line lock problem? Every single piece of the hydraulic system has been replaced except for the roll control and I still have a spongy pedal. It wil come around on the second stab and work great. I even installed a front disc conversion and went with a G.M. Corvette style master cylinder and still soft. Arrrgh!

Dragsinger · 05-10-2015, 08:56 PM

Tommy,

what about the mounting position? Might it be mounted at a high point and be trapping air?

tommy d · 05-10-2015, 11:20 PM

Quote:

Originally Posted by Dragsinger

Tommy,

what about the mounting position? Might it be mounted at a high point and be trapping air?

Its lower than the master cylinder but not by much. I am going to by-pass it tomorrow and see what I have.Thanks for the suggestion.

tommy d · 05-11-2015, 03:24 PM

Well I by-passed the line lock and the problem is still there. Anyone run a residual valve on their car even if the master cylinder is higher than the calipers?

Kenney Kelley · 05-11-2015, 07:13 PM

Quote:

Originally Posted by Tommy d

Speaking of line-locks. Has anyone ever had a spongy pedal because of a line lock problem? Every single piece of the hydraulic system has been replaced except for the roll control and I still have a spongy pedal. It wil come around on the second stab and work great. I even installed a front disc conversion and went with a G.M. Corvette style master cylinder and still soft. Arrrgh!

Tommy we had similar problem on a car we bought it had Strange brakes on the front and rear. On each caliper it has either 2 or 4 bleeders you need to bleed all of them. Also it had a Hurst line lock..We installed the rebuild kit and that fixed that problem.

Kenney Kelley

Mark Ugrich · 05-11-2015, 08:22 PM

Quote:

Originally Posted by tommy d

Speaking of line-locks. Has anyone ever had a spongy pedal because of a line lock problem? Every single piece of the hydraulic system has been replaced except for the roll control and I still have a spongy pedal. It wil come around on the second stab and work great. I even installed a front disc conversion and went with a G.M. Corvette style master cylinder and still soft. Arrrgh!

Is the pedal ratio correct for the conversion/disc brakes?

Eman · 05-11-2015, 10:28 PM

Buy a couple of plugs that will fit the MC. Plug off 1 section and see what it feels like. If it's still spongy plug off the other and try it, spongy with both plugged you've got air in the MC. If plugging 1 section makes the pedal firm you have air in the section or a hose ballooning.

tommy d · 05-12-2015, 12:06 AM

Thanks for the ideas guys. I like the idea about blocking off a chamber on the m/c and see what happens. The disc conversion company says to pick up the $30.00 Harbor Freight pressure bleeder and use it. Gonna try that tomorrow. I hear pedal ratio thrown around on other forums. Maybe I'm going to have to learn about that next. Thanks.

HandOverFist · 05-12-2015, 01:29 AM

Yes, I use a 2 pound residual valve in the rear of both the Camaro and Mustang (Aerospace 4-pistons).

Eman · 05-14-2015, 08:38 AM

Pedal ratio should be 6:1 so if the pedal is 12" long from the pivot to the bottom you want the rod attachment at 2" down from the pivot.
I guess 2lb isn't much but most class racers don't want any drag on their brakes and have gone as far as installing springs to release the calipers so the pads don't rub the rotors. Since disc brakes don't have return springs there should be no need for residual valves unless the MC is below the wheel cyl and fluid could drain back. Residual valves on old drum brake cars were to stop the return springs from pushing back the wheel cyl pistons way back and causing a low pedal. Much of that was overcome with those strainer looking things in the wheel cyl on the wheel cyl springs. Which is why they did away with residual ck valves in factory MC's years ago even with drum brakes.
You can back bleed brakes pretty simple and easy. Go buy a large animal syringe and a piece of clear tubing to fit it. Load the syringe with brake fluid and remove the air, just like you saw the nurses do before they inject you. Push the fluid back thru the bleeder with the syringe. This is OK but I've never had to do it on brakes, only on clutch hydraulic systems that were hard to bleed.. On calipers tapping the caliper with a rubber mallet will bring the air to the top and out the bleeder. Be sure the calipers are installed correctly with the bleeders at the top. I have seen them reversed and the bleeders at the bottom.

05-10-2015, 07:32 PM	#1
tommy d Senior Member Join Date: Oct 2010 Location: Indiana Posts: 830 Likes: 1,623 Liked 359 Times in 135 Posts	Re: Line lock question Speaking of line-locks. Has anyone ever had a spongy pedal because of a line lock problem? Every single piece of the hydraulic system has been replaced except for the roll control and I still have a spongy pedal. It wil come around on the second stab and work great. I even installed a front disc conversion and went with a G.M. Corvette style master cylinder and still soft. Arrrgh! __________________ Who owns this car, with the peace sign,mag wheels, and four on the floor?

05-10-2015, 08:56 PM	#2
Dragsinger VIP Member Join Date: Jul 2008 Location: Liberty City [East Texas] Posts: 1,760 Likes: 5 Liked 99 Times in 60 Posts	Re: Line lock question Tommy, what about the mounting position? Might it be mounted at a high point and be trapping air? __________________ Larry Woodfin 471W

05-11-2015, 03:24 PM	#4
tommy d Senior Member Join Date: Oct 2010 Location: Indiana Posts: 830 Likes: 1,623 Liked 359 Times in 135 Posts	Re: Line lock question Well I by-passed the line lock and the problem is still there. Anyone run a residual valve on their car even if the master cylinder is higher than the calipers? __________________ Who owns this car, with the peace sign,mag wheels, and four on the floor?

05-11-2015, 10:28 PM	#7
Eman Member Join Date: May 2014 Location: E TN Posts: 473 Likes: 16 Liked 133 Times in 76 Posts	Re: Line lock question Buy a couple of plugs that will fit the MC. Plug off 1 section and see what it feels like. If it's still spongy plug off the other and try it, spongy with both plugged you've got air in the MC. If plugging 1 section makes the pedal firm you have air in the section or a hose ballooning.

05-12-2015, 12:06 AM	#8
tommy d Senior Member Join Date: Oct 2010 Location: Indiana Posts: 830 Likes: 1,623 Liked 359 Times in 135 Posts	Re: Line lock question Thanks for the ideas guys. I like the idea about blocking off a chamber on the m/c and see what happens. The disc conversion company says to pick up the $30.00 Harbor Freight pressure bleeder and use it. Gonna try that tomorrow. I hear pedal ratio thrown around on other forums. Maybe I'm going to have to learn about that next. Thanks. __________________ Who owns this car, with the peace sign,mag wheels, and four on the floor?

05-12-2015, 01:29 AM	#9
HandOverFist VIP Member Join Date: Oct 2013 Location: Gulf Breeze, FL Posts: 1,651 Likes: 8 Liked 33 Times in 16 Posts	Re: Line lock question Yes, I use a 2 pound residual valve in the rear of both the Camaro and Mustang (Aerospace 4-pistons). __________________ Rich Taylor I/SA - 321

05-14-2015, 08:38 AM	#10
Eman Member Join Date: May 2014 Location: E TN Posts: 473 Likes: 16 Liked 133 Times in 76 Posts	Re: Line lock question Pedal ratio should be 6:1 so if the pedal is 12" long from the pivot to the bottom you want the rod attachment at 2" down from the pivot. I guess 2lb isn't much but most class racers don't want any drag on their brakes and have gone as far as installing springs to release the calipers so the pads don't rub the rotors. Since disc brakes don't have return springs there should be no need for residual valves unless the MC is below the wheel cyl and fluid could drain back. Residual valves on old drum brake cars were to stop the return springs from pushing back the wheel cyl pistons way back and causing a low pedal. Much of that was overcome with those strainer looking things in the wheel cyl on the wheel cyl springs. Which is why they did away with residual ck valves in factory MC's years ago even with drum brakes. You can back bleed brakes pretty simple and easy. Go buy a large animal syringe and a piece of clear tubing to fit it. Load the syringe with brake fluid and remove the air, just like you saw the nurses do before they inject you. Push the fluid back thru the bleeder with the syringe. This is OK but I've never had to do it on brakes, only on clutch hydraulic systems that were hard to bleed.. On calipers tapping the caliper with a rubber mallet will bring the air to the top and out the bleeder. Be sure the calipers are installed correctly with the bleeders at the top. I have seen them reversed and the bleeders at the bottom.