brakes got me stumped

[jz61]

so im at wits end! my 65 belvedere has a disc brake set up from a later model, im guessing 68 to 70 b body. its a manual system, dual master cylinder. all was fine, the one day pedal goes to floor, pump it up , seems fine. so o change the master with a new not rebuilt unit. bleed all brakes, all line look good, no leaks, not a drop of brake fluid any where. seems good, then pedal right back down to floor.WTF! start to check things out, seems the problem only happens when I turn the wheel almost to lock either way. as soon as I straighten wheel ,brakes pump rite back up, you can stand on pedal all day, firm and does not loose pressure! jacked car up took front wheels off got under car turned steering back and forth looking for kinks, pinches, leaks, not finding any thing. I car hear when steering goes past a certain point,air bubbles in the master, while wheels are turned one side or the other, can not get pedal pressure, as soon as steering comes back to center pedal will pump rite up and hold pressure! have new distribution block,and was thinking of running new lines, but I don't think that is the answer, as I don't see any evidence of leaks or loss of fluid. im thinking its something real simple that im just missing any help from anyone who has had similar problems would ne very helpfull

 

[bm02tj]

Check to see if the caliper is being pushed to bleed fluid back to master when turned to lock

 

[nm9stheham]

Check the rubber brake lines to the front calipers for any sign of bulging when this happens. These are comprised of an inner liner and outer jacket with reinforcing in between. These get old and the inner liner (which is what holds the fluid) can crack and deteritorate and the fliud will then get in between the 2 layers. Perhaps, when you turn the wheel, the lines are getting distorted and the fluid is going between the 2 layers. If the lines are more than 10-15 years old, you NEED to replace these regardless. The inner liner cracking can casue all sorts of braking havoc, including locked calipers.

Also, make sure the front lines go to the larger reservoir in the MC. If you have the front lines on the small reservoir, you will simply run out of fluid as the front pads wear (probably not an issue now). If you have 2 equal sized reservoirs, you have trhe wrong one; that is for a drum/drum brake setup.

 

[sleepar]

X2 the lines are bad do the rear one also while you are into it

 

[jz61]

Check to see if the caliper is being pushed to bleed fluid back to master when turned to lock

when you say pushed do you mean the pads in the caliper?

- - - Updated - - -

Check the rubber brake lines to the front calipers for any sign of bulging when this happens. These are comprised of an inner liner and outer jacket with reinforcing in between. These get old and the inner liner (which is what holds the fluid) can crack and deteritorate and the fliud will then get in between the 2 layers. Perhaps, when you turn the wheel, the lines are getting distorted and the fluid is going between the 2 layers. If the lines are more than 10-15 years old, you NEED to replace these regardless. The inner liner cracking can casue all sorts of braking havoc, including locked calipers.

Also, make sure the front lines go to the larger reservoir in the MC. If you have the front lines on the small reservoir, you will simply run out of fluid as the front pads wear (probably not an issue now). If you have 2 equal sized reservoirs, you have trhe wrong one; that is for a drum/drum brake setup.

im pretty sere its the rite MC and hooked up properly. I had other cars that the front brake hoses went bad, collapsed on its self, it was a dodge neon, the caliper would not release completely, it ended up seizing and lunched the rotor. im not seeing any evidence of this, what really has me baffled is that there is no loss of fluid,i will do the front hoses first , im thinking im gunna replace every component of this system piece by piece, and then find out it something really simple, on the bright side ill have a new brake system!

 

[sleepar]

Exactly... the rubber hoses are always my first step, they cause many mysterious things and they will last 100 years all cracked and dry... why people never change them is beyond me especially considering the cost to replace them very cheap insurance.... change them with tires. 5/50,000

 

[bm02tj]

does any thing touch caliper to push it towards the rotor as this will move the out board pad away from rotor

 

[jz61]

don't see any thing touching caliper, looked over and over for any interference of anykind, nada! please keep the suggestions coming! im sure with all the great minds in the room the mystery will get solved sooner or later, hopefully before I $pend too much on what turns out to be a 'DOH forehead smacker!

 

[Hemi Rebel]

When you turn the wheel all the way and push the brakes can you feel it in the steering wheel? Does it do it with front end up and the wheels off? Pictures of your set up might help. It makes no sense that it is ok with the wheels straight ahead but the pedal goes to the floor with thw wheels turned. Make certain the calipers are not hitting anything with the wheels turned. Sounds to me like the calipers may be pushing up against some suspension component. The caliper is mounted in such a way that it slides. Its a floating caliper. As the pads wear the piston extends out of the caliper and the caliper slowly works its way toward the car. Now, if you press on the back of the caliper it will slide in the direction it is being pushed and the piston will be pressed back. If it isn't something like this I'm at a loss. If the pedal goes down there is pressure loss. Either out or internally. Since it does not do it with the wheels straight and there are no obvious external leaks.

 

[rtriv]

Are the hoses being stretched as the wheel turns to hard lock? Stretching the hose could increase the volume requiring more master displacement and pedal travel to fill it. Long shot I know.

 

[jz61]

it does it with the wheels on, on the ground, it does it with the wheels off and car up on jack stands, im gonna change brake hoses and go maybe 1/2 to 1 inch longer to eliminate any chance of the hoses getting stretched

 

[Dako]

You are right...that makes no sense. I'll be following this one close.

 

[mopar12372]

are the calipers on the side of the car they belong ? the bleed screw should be on the top on the inside of the fender . make sure the rear brakes if drums are adjusted before bleeding brakes of youll have mushy pedal problems .

 

[jz61]

well the brain trust rules! props to hemi rebel and bm02! upon further review, had installed a helliwig sway bar front and rear. close inspection showed mounting braket on bottom of shock hitting caliper! loosend mount and tried to angle more towards control arm bump stop. that caused interference in that area. after lots of swearing. lot of finaggleing the end result is. grind of some of the mounting bracket for caliper clearance, raise totrion bars a good amount, and grind off some of the bump stop for additional clearance, all while trying to keep stabilizer links at at a good angle! once again a big atta boy to the FBBO members!

 

[bm02tj]

Happy to see you found it

 

[Dako]

Some photos would be great...so others know what to check for. Glad you got it figured out.