Brake problem, your expertise is welcome

PorknBeaner hit it Something has a crack in it and its separating with the force of hitting your brake

 

OK , so what's included in the "everything" that you took apart and reassembled?

 

Swap the hoses back to the way you had them originally and don't change anything else. Re-test and see what happens. As Vicky says, sometimes you have to go from A to B and back to A to prove a problem.

What else might you have altered when you "put everything back together"? If it still works fine with the hoses the other way around, change one other thing at a time until you get the problem back. The last thing you change back was the culprit.

 

my panel truck will do this at times,It has non self adjusting rear brakes.When it starts to pull,I adjust the rear brakes even and it goes away.I also have a 16 ft trailer with brakes on one Axel,if they get out of adjustment or I lose power to one side it will also pull.A old ford mechanic once told me if,one set of shoes are lose,the other side will hit the drum sending all the pressure to the lose side,making it lock up for a second before the pressure equalize.If it pulls left check and make sure left brake is adjusted same as rig th side,on the rear Axel.Then make sure both front brakes are adjusted the same.Usually if it pulls violently it will be the rear brakes.

 

Just another thing.When I was having problems with my rear brakes,I took a old drum and cut most of the front off leaving just a couple of lug holes,then put it on the Axel and had someone work the brakes,this lets you see if the shoes and springs are working right,and if shoes are contacting the drums right.

 

Take a junk wheel and weld a long bar to it ,jack up the front and see one wheel is harder to turn than the other> At least it should help figure if it's brakes or something else.

 

This is good advice.

Really, there are two ways to attack this problem. First is to change parts until you fix the symptom, and the second is to troubleshoot and find the cause. Not trying to start anything, but that is just the way it is. I prefer to troubleshoot since more 'mechanics' are needed in this world of 'parts replacers'.

I read that this problem started when you replaced the kingpins, but we both know kingpins isn't the cause here. What else was all done to the brake system since it used to brake correctly? Those things are your list of likely suspects. Less likely, but still possible, is that this problem developed by itself. That is another reason why troubleshooting is a better method.

If the steering wheel wants to rotate (as you said it spins hard when not restrained) when braking at even slow speeds, I doubt it is an adjustment or return spring issue. The difference in braking between sides is either mechanical or hydraulic. I think the issue is more likely to be hydraulic as you said you are very experienced with these brakes. A siezed cylinder or incorrectly assembled brake assembly would have been obvious to you. I also think the problem is more likely to be at the front wheels than the rear - rear wheel braking differences will indeed create a pull, but not jerk the steering wheel out of your hands. The 'scrub radius' is what causes front braking differences to affect the steering so strongly.

As mentioned by someone else, pressure testing is an ideal way to troubleshoot the hydraulic aspect of this problem. The simplest way would be to apply some pressure to the system and then open a bleeder. Repeat as identically as possible for the other three wheels (do all four just to be completely sure - best troubleshooting is that which is thorough). If one doesn't squirt fluid out as far, then you can zero in on the source of the pressure difference. Pressure gauges are even better, perhaps you could rig up something attached to brake bleeders (threaded fittings welded onto extra bleeder screws?) to connect gauges to. Although brake pressures can be quite high, low to moderate pressure troubleshooting may catch the problem here since it is so severe. Just have a helper apply brake pedal pressure as you watch the gauges. Obviously, don't let them overpressurize and 'blow' your gauges. Cheap gauges are good enough to catch what you are looking for if you don't have the right ones, or don't want to take a chance of wrecking your good gauges.

The concept of a 'check' (something acting as a check valve) or clogged hose/line seems very very likely. Is it possible that there is something foreign in the hydraulic system that is acting as a check valve? Obviously, you wouldn't put stuff in the hydraulic system, but strange things can happen especially with cheap remanufacturer labor. I have heard of that happening, but thankfully not to me in my experience. I think just to make sure that is not the case (remember, be thorough!), I would loosen one brake bleeder and then have your helper give the brake pedal a somewhat fast, complete stroke. At the bottom of the stroke, tighten the bleeder screw. Repeat for the other three wheels. This is different than the previous crack-the-bleeder pressure test performed earlier, as this time you are looking at the amount (volume) and flow rate of fluid coming out. A reduction of volume or flow rate means theres a restriction, and that is what a 'check' would certainly cause. I have experienced once a hydraulic hose that was clear enough to see light through, but would be restricted when under pressure.

For the braking to be balanced on both sides, many things have to be somewhat equal. You know the adjustment affects the time it takes for the shoes to contact the drum. You also know the coefficient of friction affects which ones brake better. Those are some of the mechanical factors. Just as important are the hydraulic factors - namely brake fluid flow to the wheel cylinders and the resulting pressure that is built up within them to apply the shoes.

The best troubleshooting checks everything and assumes nothing. Good luck.

 

I had a 84 chevy pu just bought it and front barke left side was heating up.I let it sit for some time and seemed ok went for a drive same thing brake locking.I changed caliper same thing,took it back and said it was no good.Got another one same thing.Changed Master cylinder still same problem.
Whats left the rubber line,changed it and no more problem.Someone pinched the line and damaged it.Never pinch the line or swist it.

 

These wild goose chase threads get folks thinking. Usually off the wall obscure unicornitarian thoughts but what the hell. Generally it ends up being something simply overlooked or taken for granted that is good when its not. Sometimes it the methods or equipment leading to a bad diagnosis.

99 out of 100 times when a hose goes bad it stops the flow back to the master and creates a condition like you described. Brake dragging.

I suppose there could be a flap inside the hose that flips shut blocking fluid flow to the Wheeler cylinder. It would have to resist the pressure and get tighter as the pressure increases. I also would believe that the OPs problem would follow that hose when swapped side for side.

 

Yep, you may have put it back together correctly this time and fixed the problem without knowing it.

 

Or there are 2 wrong things and the changes cancelled each other out.

Bob

 

I had a 55 T-bird do the same thing. A rear wheel seal was leaking oil onto the shoes and making that side pull.

 

When you use a "shot gun" approach at anything , you really have no idea what the problem is or was.
On the other hand , if you dont really care to know the "shot gun" gets it done.

Over the course of two years , its hard to remember what's been done, tryed and re done.
Best thing to do is probably what happened. Blow the entire thing apart down to every nut bolt pin bushing and "re-rebuild" it. Careful inspections on take down and put back should catch it.

I still say that if its so violent that it jerks the wheel out of your hand , it should be obvious. Maybe it would take Two people to see but still obvious. Again on a tear down-obvious.

 

O.K., let me get this straight, I didn't read all this stuff, but the owner "manyolcars", indicated he swapped the hoses on this truck. Side for side. Then he indicated it went away, very good chance it was a piece of crud that got dislodged when they were taken off. A hose can deteriorate internally and become a "check valve"! I have dealt with this about 6 times, it usually happens in that one wheel or axle won't release, then they drag and get hot! He may have it fixed, but he should look at those hoses to be sure! This is one of those "head scratchers" that will drive ya to drinkin', but usually is something VERY simple in the end!

 

Just to add to what's been said above , You need to remember that when the fluid travels to the wheel cylinders it is under pressure .... When returning to the master it's not under pressure . Hence if a hose has been pinched , tweaked pulled or damaged internally it is inclined to act like a check valve .


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check rear brakes

 

Okay, you switched hoses from side to side and now have equal braking.

I would agree with your thought that there should now be a pull in the opposite direction if there was a bad hose.

Now, this is just a wild ass guess here, but what is the chance that the hose flexes one way in one position and pinches itself off but when switched to the other side it flexes in the opposite direction and remains open?

Like I said, just a guess. Like someone else said, when hoses get restricted they usually allow pressure to the wheel and do not allow release but I've had a few lately do the opposite.

Hope this helps, good luck.

 

you also can tell if a line is clogged by feeling the difference in brake pedal drop when a bleeder is opened. you will notice a difference in speed and force to depress the brake fro one cylinder to the next.

 

Sounds like your on the right path! Hope you get it all figured out have a safe cruise!