Brakes still randomly build pressure to cause undrivable dragging, everything replace

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the hard lines run about 2 fingers away from the headers and they run down it about 6 to 7 inches. THe hard line curves down towards the axle right at the top of the header and follows it straight down to the mount on the axle and it stays tat close the whole way. I only drove it about 1/4 of mile when the brakes started to bind and sill was able to drive it into my grage. Right away I put my hand on the back of the wheel and it wasn't hot. I was able ot keep my hand there and it wasn't the slightest bit warm, but the brake fluid steamed in the res. cup on the vac. pump.

So I know the brakes aren't hot enough to heat the fuid if I can put my hands on the bleader valve and it was at room temp, but the fluid is warm enough to see a tiny bit of steam. It wasn't boiling with a huge amount of steam, just saw a little wisp of steam for a second in a hundred degree garage. It was very warm until it was in the air for a minute and cooled down right away.

I will move the brake line tomorrow. Once i Released pressure to blead my brakes were working fine so it will ahve to be blead and driven to see if it happens again.

After that, I will have to go with another master if it isn't the heat.
 
And outside the framerail with the brake line will expose it to more risk of damage or failure. I have been watching your thread from the start because I am having the same problem. Good find! thanks.
 
Only 2 fingers away from the header would be a problem . I'm thinking heat=brakefluid expansion. may not boil the fluid but get it hot enuff to expand in the line causing pressure, and the brakes would dragg.
sounds minimal but it may happen.
I will move my line to the front of the motor mount inside the frame right above the axle, it will bring my line another 6" forward away from the header , possible might have to make another line thats longer
with coils ,maybe a shield attaced to the master cyl. could all be for nothing
 
303garage said:
Only 2 fingers away from the header would be a problem . I'm thinking heat=brakefluid expansion. may not boil the fluid but get it hot enuff to expand in the line causing pressure, and the brakes would dragg.
sounds minimal but it may happen.
I will move my line to the front of the motor mount inside the frame right above the axle, it will bring my line another 6" forward away from the header , possible might have to make another line thats longer
with coils ,maybe a shield attaced to the master cyl. could all be for nothing
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303garage, I like the way you're thinking. Slickrock, I have been considering your issues. Your conclusion begs some answers. One, what is the weather like where you live. I am thinking that if it is near 100% humidity then that might explain the vapor you noticed. Did you have fresh brake fluid in there? Brake fluid boils at over 400 deg. f. If you have fresh fluid (very little water in the sys.) then I have to question your conclusion. To get hot enough to boil water the BF would have to be scalding. Heat tranfer down to the BF for that brake line is driven by a temp too low to boil BF unless maybe you are running really rich. Anyways, if heat was the root cause then the back pressure on your brakes should be released every time you step on the brakes. One thing I think you could do is to pull the pin that connects the brake pedal to the booster rod. Back out the stop switch, Hold the pedal at FSM spec and look up there. Look to see where the c. rod pin hole lines up to the hole in the brake peddle. Adjust to align. That way, you know that that is not the issue. The booster mech. neeeds to be at a centered balanced position when at rest in order for the system to function properly. Here, a picture.
 
Of course, you will also want to have the return spring disconnected. This is how I did it on my 55. Good luck.
brakepeddle1.webp
 
Interesting thread. Looks like you might be onto something with the heat thing.

I'll just throw a couple things out there for ya anyways.

1) Buddy has one of his calipers lock up on him solid. Let it sit for a while and it was fine. Pump the brakes and it was locked again for about 15minutes. Turns out the inside of the flexible brake line was screwed up and somehow acting as a check valve. Replaced the line and it was fine.

2) Another friend put discs on the back of his cruiser. It would gradually lock up tighter and tighter the more you used the brakes. Turns out he forgot to pull the residual valve out of the mc when he went from drum to disc. Removed the residual valve and it fixed it.

3) I had a situation where light driving was fine but I got in a traffic jam and kept having to do stop and go type driving. One caliper heated up bad and was dragging and smoking. Turns out that a long downhill the previous year had heated up my brakes so much it made the piston boots get brittle. They disentegrated slowly and water got into there and the pistons started to seize up with rust. Short drives with light brake application didn't show the problem but lots of pumping the brakes really showed the problem. There was not enough "rest" in between brake applications so as to allow the piston some time to retract. New calipers fixed the problem.
 
rsbcruiser said:
303garage, I like the way you're thinking. Slickrock, I have been considering your issues. Your conclusion begs some answers. One, what is the weather like where you live. I am thinking that if it is near 100% humidity then that might explain the vapor you noticed. Did you have fresh brake fluid in there? Brake fluid boils at over 400 deg. f. If you have fresh fluid (very little water in the sys.) then I have to question your conclusion. To get hot enough to boil water the BF would have to be scalding. Heat tranfer down to the BF for that brake line is driven by a temp too low to boil BF unless maybe you are running really rich. Anyways, if heat was the root cause then the back pressure on your brakes should be released every time you step on the brakes. One thing I think you could do is to pull the pin that connects the brake pedal to the booster rod. Back out the stop switch, Hold the pedal at FSM spec and look up there. Look to see where the c. rod pin hole lines up to the hole in the brake peddle. Adjust to align. That way, you know that that is not the issue. The booster mech. neeeds to be at a centered balanced position when at rest in order for the system to function properly. Here, a picture.
Click to expand...

I have done what you suggested with the push rod. Took the measurements and left factory space between the push rod and MC. You need to realize, the booster is the 3rd booster and the master is the second. THe calipers are replaced with working calipers from another rig. The onlythign that is not new is the brake line.

As for the temp, it was 100 degrees wth 30% relative humidity (jsut heard the report on my weather band CB on the way home).

Also, remebr the back of the brakes were cool. No heat comming from them. Once I bleed the brakes, they worked fine and a wisp of steam surprised me.
 
My plan for Monday is to order a new Master Cylinder, move the brake line to the outside of the frame rail (It will be in a safe location), disconnect the brake lines at the back of the caliper and blow air through it since I will have to install a new master and bleed anyways. I'll keep everyone posted.
 
A wisp of steam? Man, this is a tough one Slickrock. I feel your pain. Being there, doing that. I dwell on the basic adjustment issues because when you think about it, there are so many ways to go wrong here. The padal side P.rod, the stop light switch and the MC P.rod. Any one or worse a combination of incorrect settings and then things starting getting wierd. I am trying to go back to the FSM basics to chase it down with my rig. Attached is a pic of the pushrod, do you own calipers? Might pin it down a little for you. The FSM says to adjust the MC P. rod next. Looks like they ask for a clearance of 0.02". Hmmm, heard different somewhere. But, 0.02" is not much, a quater turn or less on the adjustment. The headers as a heat source? IDK, I like the suggestion of giving it a temp heat shield to help figure it. My experience, every time you alter a system from stock you are asking for trouble. No heat in the brakes? Lordy, Sliprock hope you get this one figured. I sure would like to hear what it was when you do. I run a SS flex line there. Similiar problem for a friend resulted from a piece of metal in the steal hard lines acting as a one way valve. Drove him nuts before he found it. I like your plan to blow back the lines. Suggest using the lowest pressure possible and working up so that you might be able to detect the issue. and going both ways when blowing through. This sure is one of these:bang:.
pushrod.webp
 
maybe I shouldn't have thrown in the newbe header thought, my bad. I sometimes think too hard for something that is way to easy to figure out. never rule out the basics. my way of thinking is somewhat
backasswards, I will be going through my brake system also so I will follow this hard, hoping to learn from you guys. stock booster master cyl drums all the way around I have absolutly no brakes as of right now.
but you wont see it on the road untill then. Slickrock, rsbcruiser, goodluck.
 
Blokeman said:
Perhaps a temporary heat shield, foil or something around the line in the hot spot, may help eliminate this as a suspect, a quick drive around may save you a lot of fiddling...
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I wish that were the case. I drove the rig for two days this time before it happend. Most of the time it is after a few miles on the hwy, sitting after hyway driving getting gas, or on a trip. I never know when it will happen. Since I am getting a new master, I migh as well move the line since I will be bleeding the hole front system. I need to take the line out to blow air thorugh it anyways.
 
rsbcruiser said:
A wisp of steam? Man, this is a tough one Slickrock. I feel your pain. Being there, doing that. I dwell on the basic adjustment issues because when you think about it, there are so many ways to go wrong here. The padal side P.rod, the stop light switch and the MC P.rod. Any one or worse a combination of incorrect settings and then things starting getting wierd. I am trying to go back to the FSM basics to chase it down with my rig. Attached is a pic of the pushrod, do you own calipers? Might pin it down a little for you. The FSM says to adjust the MC P. rod next. Looks like they ask for a clearance of 0.02". Hmmm, heard different somewhere. But, 0.02" is not much, a quater turn or less on the adjustment. The headers as a heat source? IDK, I like the suggestion of giving it a temp heat shield to help figure it. My experience, every time you alter a system from stock you are asking for trouble. No heat in the brakes? Lordy, Sliprock hope you get this one figured. I sure would like to hear what it was when you do. I run a SS flex line there. Similiar problem for a friend resulted from a piece of metal in the steal hard lines acting as a one way valve. Drove him nuts before he found it. I like your plan to blow back the lines. Suggest using the lowest pressure possible and working up so that you might be able to detect the issue. and going both ways when blowing through. This sure is one of these:bang:.
Click to expand...

Thanks for the pep talk. When I measured the pus rod, I measured how deep the shaft was in the MC until it was activated. I then measured from the mating surface on the BM. Once (Not the bolts, the little round part inside that the MC sits upon). Once I had this equal, I backed it off .02 or about a 1/4 turn. SO when the brake is not applied, it will not push on the MC. There was no pressure applied to the MC while I put it on the BM. So I know it wasn't connecting. My brakes worked great. The only drag I had on them was the correct amount on the wheels when I adjusted the calipers. Adjusted until they would not turn, Applied brakes to seat, backed off until the slightest drag. Repeated 3 more time. Remember, proven working calipers from another rig, new brake pads, turned drums.
 
303garage said:
maybe I shouldn't have thrown in the newbe header thought, my bad. I sometimes think too hard for something that is way to easy to figure out. never rule out the basics. my way of thinking is somewhat
backasswards, I will be going through my brake system also so I will follow this hard, hoping to learn from you guys. stock booster master cyl drums all the way around I have absolutly no brakes as of right now.
but you wont see it on the road untill then. Slickrock, rsbcruiser, goodluck.
Click to expand...

It is a long story about how I got the cruiser, but it was a trade to a buddy who owned a 4x4 shop for labor. I got it because my buddy owed me a favor for helping him redo his kitchen for free.

He knew nothing about the rig when I got it. A box was in back including a newbrake booster. I guess I now know why. The PO probably had brake problems and was trying to fix it before my buddy got it. By the way, I tried that booster too and no love. The headers were on the rig when I got it.

If this next step doesn't work,, I have no idea where to go from there. I guess I will be forced to do a disk brake conversion. Anyone have those parts for me to purchase?
 
Slickrock,

I've gone through this exact problem with my '73. In the end my soft lines had collapsed. Change ALL of them, especially the one you used the vise grips on. I too had to isolate my rear brakes and used vise grips to do it. I cut the old line open lenght wise and sure enough the inner ,rubber, liner had broken down into little pieces and blocked the passage way. Right where I had put the vise grips! I have also had soft lines collapse on an old Dodge Polara, caused me fits for months.

It sounds to me like you have the adjustments done per the FSM. I tend to doubt that you would have the same issue with that many MC/ booster combonations. Time to look else where.
My 2cts.

Jr.
 
When I got home (that was fun but it didn't totally lock up until I got in the garage), I pulled the vac. hose and tried to push the brakes. Hard as a rock. So I started bleeding brakes and of course the pressure let up. I even went as far as getting some RTV and put it around the vac line plug since it seemed loose. Thought maybe it could be loosing pressure there. I could swear I heard a new whistle as I was driving back and it seemed to be a bit louder before it happened. But then again, I could be reading at this point.Is it a vacuum related issue?
I was reading over the old posts here and was wondering when you changed out the boosters (3 of them?), did you replace the check valve or just plug the old one back in every time? maybe your building up more vacuum than whats needed , randomly.? just another thought,a faulty check valve.
Or could this cause the problem described here?
-GREG-
 
Slickrock, rsbcruiser, this is why I thinking to look at the booster check valve, Greg.:hhmm::meh:
could it be this simple, something over looked.probably not but its just another idea.
this was all taken from the first post, deleted some of it.


When I got home (that was fun but it didn't totally lock up until I got in the garage), I pulled the vac. hose and tried to push the brakes. Hard as a rock. So I started bleeding brakes and of course the pressure let up. I even went as far as getting some RTV and put it around the vac line plug since it seemed loose. Thought maybe it could be loosing pressure there. I could swear I heard a new whistle as I was driving back and it seemed to be a bit louder before it happened. But then again, I could be reading at this point.

Last time this happened, I could put on the brakes, turn the engine off and I would get the correct foot feel from the peddle to indicate no vac leak from the booster and the Master is new.



slickrock said:
1973 FJ40 Drum to drum



I keep having a repeating break issue and I am totally at a loss at this point. I have replaced the entire system (except for the rear cylinders but they are in good shape) and still it does this . . . .

After driving for a week or two or on really long trips, my brakes tend to slowly build pressure until they finally start to drag on the breaks and I have to pull over and pop the master off and turn the push rod down. This is totally random. I can drive for 300 miles or 3, it totally seems to be random.


Here is what I have done in the past to fix this problem.

1. new brake master
2. new brake booster – same issue starts up
3. mini-truck booster – same issue starts up
4. now an FJ 60 booster which stops much better but it started up again last night.
5. new calipers in the front
6. brakes adjust per FSM (adjusted to where wheel stops after hard rotation and backed off the required number of clicks)
7. bled and more bleeding of brake line.
8. Nothing is original with the braking system except rear calipers.



I did notice that once, right after start up from sitting for a few days, I had a soft pedal and pumped the pedal once and the brakes were good. But yesterday, the same old thing started happening (not as bad), but when I pulled into my driveway and took my foot of the brake and put it in neutral, the rig did not roll back. I went inside for a few hours and came back out to put it into the garage. I started it up, pulled the parking brake and it started rolling back. Obviously the pressure let up.

What is going on here? Remember, front has new cylinders, rear or original but I took them apart and they are in great shape with no leaks or anything that would indicate blow by or leakage. When I have my foot on the brakes and turn off the rig, I get a good amount of pressure push back in the pedal.



Are my break pads just adjusted too tight and as heat builds, they expand and start the drag?



Is it a vacuum related issue?



]
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I just read trough this entire thread and as random as your problem seems to be yet it is consistent in the manner that it occurs. This has me qustioning the possibilities.
1. Would pushrod clearances cause such a random problem?
2. Bad softlines would occur at either front or back or individual wheels wouldn't it?
3. Trash seems to me to be the one thing that would act so random as you describe and I would assume something in the master or a proportioning valve or something common to the whole system?

I am just a lurker that is anticipating having some of these same problems down the road in my build. I really don't know that much but trying to make the most logical sense of all the suggestions you have gotten from others that probably do know something. I am interested to see what your final solution is. Good Luck
 
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