Line Lock problems!!!!!

-
Coffee&Cars

Coffee&Cars

Well-Known Member
Joined
Nov 15, 2014
Messages
247
Reaction score
147
Location
12 miles from the track, Ohio
I am having problems with my line lock system. At the porp. valve, one line "out" to the to the front brakes has a plug. The other front line from the porp. valve leads to the line lock valve. From the LL valve it goes to a T-fitting and splits to the front brakes. The break system is healthy, Willwood disks on the front, they work just fine, but when the LL is engaged it will not hold the front brakes. not even at idle. I have check all the lines for possible pinching of the installed lines and did have to replace one, (the line replaced goes to the passenger side brake). It looked like it was formed with out the use of a bender so I replaced that part of the line. Also previously when I was bleeding them the passenger side did not flow out as well as the driver side. Since I replaced part of that line it now flows fine. And I checked all the lines forward of the T-fitting all the way forward to both calipers. They are all free flowing but they still won't hold!!! With the wheels off and off the ground I manually checked each front brake with the LL applied. I put a breaker bar between the wheel studs to turn the hub. I can not make the drives side turn but I can make the pass. side turn. Next I checked the caliper on the passenger side. I thought maybe I have a have some frozen pucks in the caliper. They are not seized, all four pucks are moving. The only thing I thought strange is the outboard pucks are extended out further than the inboard pucks.
The LL unit is a Biondo unit. When I first got the car they would not hold either. I replaced the unit with a new one. It did the same thing. The only difference with this one is the mounting bracket broke off the main body. So, I got another one (the 3rd Biondo LL unit). This time the bracket did not break off but the LL will still not hold. As I said, with out the LL, the brakes work fine but when you apply the LL they will not hold. Yes I know the LL is a one way valve and it is installed properly and you can hear the click in the unit when you apply it. I can still turn the Pass. side with a breaker bar but not the driver side. And when on the ground when applied the car still can't be held even at idle. The drivers side does not lock up either when HP is applied, it turns like the pass. side. Are the Biondo units just junk or what?? Also, I checked the previously installed union to the pass. side against the new union I installed. I found the old unions internal diameter was not as large as the new union. So reamed it to the size if the new one hoping that the reduced internal diameter was the problem. But it made no difference. Also the brake fluid is all clean and new. The break pads are worn about half way. They are not oiled or impregnated with rust from the rotors. I am stumped!! Help!
 
If you applied the brakes after you engaged the LL, you probably hurt the LL. You must apply the brakes first, then engage the LL, while holding the brake pedal. After the LL is engaged, you can release the pedal. Ask me how I know. Happened with the first one I installed, last year.
It is actually a safety feature, so you will still have 4 wheel brakes, if you inadvertenly have the LL engaged.
 
Charrlie_S said:
If you applied the brakes after you engaged the LL, you probably hurt the LL. You must apply the brakes first, then engage the LL, while holding the brake pedal. After the LL is engaged, you can release the pedal. Ask me how I know. Happened with the first one I installed, last year.
It is actually a safety feature, so you will still have 4 wheel brakes, if you inadvertenly have the LL engaged.
Click to expand...
No that's not the problem. This is not my first rodeo
 
Might be time to rig a pressure gauge in the front and see what's going on. Maybe you are not developing enough pressure in the first place. I had to go look up the destructions, it would have been nice if you would have posted a link to the device.

Is there ANY chance you have the valve backwards?

https://static.summitracing.com/global/images/instructions/sbr-ll.pdf

Maybe some were marked / assembled wrong, who knows
 
Why do you have a prop valve in the front? just run a adjust one on the rear line none on front.
 
If you are using the safety valve, the one with the switch that turns on the brake light on the dash if there is a pressure problem. When you release the rear brakes by letting off the pedal the pressure on the front pushes the valve and you loose your front pressure.
 
The valve is installed in the proper direction. So your saying and according to the instructions you show, I should by-pass the porp. valve completely? Taking the master cylinder line directly to the LL. If you do it this way do you not defeat the purpose of the porp. valve to balance pressures between front and rear brakes? As I mentioned the brakes work fine without the LL engaged.
 
brian6pac said:
If you are using the safety valve, the one with the switch that turns on the brake light on the dash if there is a pressure problem. When you release the rear brakes by letting off the pedal the pressure on the front pushes the valve and you loose your front pressure.
Click to expand...
There is no safety valve, the factory dash is no longer installed
 
Coffee&Cars said:
There is no safety valve, the factory dash is no longer installed
Click to expand...
might help to know how old a car ur working on. Sounds like u don`t have installed right, or air in the pass side line (which is harder to get out than the short drivers side)) or ur working thru some later model splitting block. Can u post a drawing on here? ( I couldn`t ) , but it would help.
 
Coffee&Cars said:
The valve is installed in the proper direction. So your saying and according to the instructions you show, I should by-pass the porp. valve completely? Taking the master cylinder line directly to the LL. If you do it this way do you not defeat the purpose of the porp. valve to balance pressures between front and rear brakes? As I mentioned the brakes work fine without the LL engaged.
Click to expand...

No you need a way to balance the front to rear so install a adjustable valve in the rear line. That's the way I have always done it and it works fine. Master to LL to front calipers.
Master to rear adjustable valve to rear brakes.
 
brian6pac said:
If you are using the safety valve, the one with the switch that turns on the brake light on the dash if there is a pressure problem. When you release the rear brakes by letting off the pedal the pressure on the front pushes the valve and you loose your front pressure.
Click to expand...
Brian this car has the original porp. valve. I do notice there seems to be a post for a electrical connection on the porp. valve. Could it be doing this? If I understand this right after I apply the line lock and release the brake the pressure is being redistributed inside the porp. valve reducing the pressure through out the whole system?
 
famous bob said:
might help to know how old a car ur working on. Sounds like u don`t have installed right, or air in the pass side line (which is harder to get out than the short drivers side)) or ur working thru some later model splitting block. Can u post a drawing on here? ( I couldn`t ) , but it would help.
Click to expand...
This is the 1970 duster in my avatar. It is the factory porp. valve, original equipment for a disk brake 340 duster
 
Coffee&Cars said:
Brian this car has the original porp. valve. I do notice there seems to be a post for a electrical connection on the porp. valve. Could it be doing this? If I understand this right after I apply the line lock and release the brake the pressure is being redistributed inside the porp. valve reducing the pressure through out the whole system?
Click to expand...
I just don't get it. the line lock is after the porp. valve so when I release the foot brake it should release all pressure behind the LL
 
Coffee&Cars said:
Brian this car has the original porp. valve. I do notice there seems to be a post for a electrical connection on the porp. valve. Could it be doing this? If I understand this right after I apply the line lock and release the brake the pressure is being redistributed inside the porp. valve reducing the pressure through out the whole system?
Click to expand...

Yes it might be, when you appy the brakes there is pressure on both sides of the valve holding it centered, if a line fails the pressure goes to one side and pushes the valve and that grounds the switch turning on the light, you could test it with a bulb 12v on one side and the other side to the switch. if you release the brakes with the line lock on if it pushes the valve the light will come on.
 
This isn't your first rodeo so this is something I'm sure you've done although you didn't state if you pumped up the brakes to build pressure before applying the line lock? My ll won't hold even at idle unless I pump the brakes before applying the ll.
 
Jeffsrt said:
This isn't your first rodeo so this is something I'm sure you've done although you didn't state if you pumped up the brakes to build pressure before applying the line lock? My ll won't hold even at idle unless I pump the brakes before applying the ll.
Click to expand...
mine will hold after a just normal stop.
 
mine also, 1 hit on the pedal hit the LL and let off the brakes and the front wheels were locked tight
 
This is so simple
The LLs job is to prevent the brake fluid from returning to the M/C. Yours is not doing that.

But you have another issue as well.
One caliper is locking onto the rotor as per the design while the other is not. Both calipers receive their fluid from the same T-block right? Well in order for one to slip,there has to be something wrong in the circuit or a mechanical problem in the sliders or pistons, or bent pads.

Now, the piston for the safety sw in the C-valve is sealed from both sides. It can sense a difference in front to rear pressure, and then turn the dash light on. But it is sealed from both sides, or is supposed to be. But it doesn't really matter because your LL is installed between the the C-valve and the new T-block. So even if that piston was leaking it would not affect the T-block. Neither can the rear system affect it, cuz it too is on the wrong side of the LL. So the LL is just not powerful enough to keep the fluid from returning.
Since this is your second or third Biondo, I suggest a different brand.
But I would still look into the RF failure to lock onto the rotor.

BTW
I have an old Hurst set-up from the 70s. If I didn't set it right initially, I can add hydraulic pressure without resetting the solenoid.The fluid will pass freely forward to the calipers from the M/C. Sometimes I use it as a hill-holder with my stick car.I use a separate toggle sw for this, cuz like who wants to hold the momentary for two minutes, right?lol.

Because you have one unused port on the C-valve, if you wanted to, you could plumb a gauge in there And see exactly what's going on.
 
Last edited:
Thanks for all the help guys. I did trouble shoot this system which did included all of your suggestions. I even called Biondo. I guess I just had a run of bad luck with this product. As it turns out the units were defective. The LL now works with a working Biondo unit. I am so glad. Changing to a different unit would have been difficult. As you all know there is not a lot of room in these A-bodies with a big-block in them and with a mid-mount plate there is even less. I was so worried that the lines were pinched to reduce flow I did remake a few lines that were already there. Then just for the heck of it I took one of the LL apart. WOW!!! I was amazed. The hole that allows the brake fluid to pass through inside the LL to your whole front braking system is only about .010 in diameter.
If you apply the LL and then pump your brakes it will work. All you are doing is forcing the seal off it's seat witch allows fluid to pass through. When you release the pedal the valve will return to it's seat to hold what ever pressure you applied. It's basically a one way valve. The clicking you hear when you apply it is the electro magnet pulling the piston with the seal into place. So if it clicks you know the magnet is working if it won't hold then the seal in the end of the piston is bad. Take one apart , you'll be amazed. If you want the cheap way out on this part buy one or accept one from someone is giving it away that is claimed to be defective and rebuild it. I will next time. Thanks .
 
You must log in or register to reply here.
-

Back
Top