Sticky Brakes

I gave you a GA. 1994 good guess. For some reason these brake pads do not retract. Some brake pad holders, or the pads rust and block.

Does a DRUM brake have a caliper? Or have I misunderstood the question ?

It doesn't. Same concept, but cylinder is the correct term. Bricktop's comment still applies.

nice pic, I'd say you got your monies worth out of that one

I just pulled it off the web. Another typical cause, (at least on GM front brakes), is an internal collapse of the flexible hose that runs to the brake.

I think you got a GA for that answer, at some point. I don't know if it applies to rear Ford brakes.

My question had a reason: in a caliper brake (disk) the pistons are pushed back by the brake disk itself. In the case of the drum brake, as far as I know, there is a spring which pulls shoes from drum away. Could it be that the sticking of the cylinder correlates with a softened or not put in place spring ? Or may be I know only OLD designs and modern ones do not have a spring but shoes designed to pull back although I do not see how since the aerodynamic forces are low in comparison to possible disk action. Any way in the picture I do not see which element will pull shoes away.

These vehicles have disk brakes in the front and drum brakes in the rear. That means that they have a compensating/proportioning valve and a hybrid master cylinder with two different sized reservoirs.

You are right about the springs in drum brakes.

The springs would hook around the round post in the center of the cylinder, maybe.

Many times the hooking post is separate and above the cylinder:

I see that the F150 has flexible hoses going to the rear brakes. I would change those first. A bad piston seal in the master cylinder would affect all four brakes.

Drums, not discs. RTFA!

We'll put Carnac right on it.

Did this just start?

Did you just "fix" them?

The lack of information you supply is impossible to decode.

Clogged lines?

Bad shoe adjusters?

Maybe a bad equalizer valve?

Your master cylinder has one large and one small side, right. Front/back.

Give something to work with here.

Good Questions.

1)Rear brake shoes/drums locked up and destroyed them selves. Front brakes/pads work fine.

2) Replaced all components (shoes, wheel cylinders,drums, cables, hardware)

3) Take truck out exercising brakes and come back with rear brakes overheated.

Fronts brakes are okay.

4)Evidently the brake system pressure is not being relieved when letting up on brake pedal.

Where is the hang up? master cylinder, etc??

That's both rear drums right?

When the rear brakes shat themselves per #1 what actually happened? Did they suddenly lock up? Started dragging with progressively more drag until they seized? Any other history?

Post a photo here.

The master cylinder is a very good place to start.

The next time it happens, check this out:-

Jack up a front wheel. Try and move a wheel, if difficult, do the following:-

If you get a brief jet of brake fluid when you open one of the air bleeds on either of one of the front brakes and the brakes are "free" again! (Wear goggles!)

Then it is the master cylinder.

Either it has been installed/set up incorrectly, or its possible that something is stopping the brake pedal from fully returning when released.

The list is long.....

Start by simply trying to pull the brake pedal back up, even a small amount could be the problem. Lubricating the "axle/pivot" of the pedal may fix this.... If this is all OK, then a proper adjustment may need to be performed of the brake pedal/Servo/Master cylinder.

Best of luck.

Does your action have any influence on the rear brakes ? The question concerns the DRUM brake which are as writes Lyn on the rear.

Naturally, all brakes are affected.

In a dual system, one front and one back brake are on the same circuit, so you may need to do it to the other front brake as well to get it to free up till the problem is found and fixed.

Here is a good "primer" for anyone wanting to understand brakes better:-

http://en.wikipedia.org/wiki/Hydraulic_brake

I've never seen that system. All of mine have been like this:

With one reservoir for the rear brakes, and one for the front.

According to several articles on brake system, the US was the first with split systems and that it has been general for many years. Either side to side or front rear.

What you show is a car with probably a front/rear split, why? Because you have two lines coming from the master cylinder.

On a single system, there would be only one. The unit in the middle is a front/rear balancer.

It may be quite difficult otherwise to identify a front/rear split from an older car with no split!!! Personally never tried! But looking for the number of hydraulic feeds from the master cylinder is a good tell tale....

I don't know if its required by law either in the USA or anywhere else for that matter, but I have not actually thought much about it, but I sincerely believe that most cars have split systems nowadays.....but the loss of one side WILL result in a major problem with stopping......it will feel almost like no brakes at all....

I wonder how the ABS & ESP handle a leak?????

The last car that I ever KNEW had no split system was made in the 60's.....It had no servo either, and only drum brakes....

but the loss of one side WILL result in a major problem with stopping.

This is what I was talking about. Every split system I've ever owned, (which is everything), was split between front brakes and rear brakes; not side to side.

I can't imagine designing something like that. It seems like the loss of one side, during a high speed emergency braking situation, would result in an immediate roll.

You are missing an important fact.

The link I recently posted also mentioned it. It tells in the link how the split is front one side with rear of the other. Obviously not a perfect balance, but nowhere near as bad as you seem to imagine.....

I believe that I have read somewhere that some systems have 3 or even 4 circuits, front right, front left and rear pair/singles, maybe someone can confirm or deny this (being too lazy and short of time to do it myself!!) Probably through ABS/ESP as it is there to control each wheel separately!!

I must admit that I have never personally had such a loss of brakes/fluid in the manner we are talking about and therefore achieving only "half a system".

Though in 2001 I had a new car that if I drove much over 200 KMH for a few minutes or more, then completely refused to allow the brake servo to assist my braking!!! That was a good as having no brakes at all!!

Very scary. The Dealers (4 different ones!) changed the servo four times with no effect on the problem. But a change of the master cylinder AND the servo did finally fix it.....so I guess it was the master cylinder, but no one knows how or why.....

No one (including myself, though I had as good as no say in the matter!) ever thought to change the master cylinder on its own....and I was sick of putting my life on a limb with testing as the fault only happened about once a month at the most....(enough to kill anyone still!)

I found it. It's a new one on me. Mine have always been fronts and rears on separate lines. It still looks like a recipe for a rollover situation.

http://vnc.thewpp.ca/stuff/bentley/ep0niks.ctech.ca/vw/eva2/SU02/ch1.1.html

Rolls uses a very different design for the power brakes. They use pressurized hydraulic fluid and allow it to go the the wheel only when you step on the brake pedal. And the split is different also. The front calipers have two separate circuits in them. The system uses one front piston combined with the rear caliper, of both axles. The other system uses the remaining front piston of the front caliper. I just do not remember if there was a crossing of side to side or not. This Rolls was an 84, or close to it.

There are, or were some European systems that split the system diagonally. left front and right rear on one side and right front and left rear on the other. Andy, can you shed some light on this?

Look here for some good diagrams, its a PPT presentation:-

How Split Brakes Work

Its a slow loader though.

The diagrams of the inside of the master cylinder are clear and also correct!!!

The system became standard on 1968 vehicles sold in the US. I believe it was used on some American Motors vehicles before that.

Brakes sticking at only one front wheel..1.Flexible pipe broken on the inside causing a one-way valve or 2. Caliper needs to be overhauled.

Both front wheels sticking...1.Check pedal rod play or 2.Overhaul master cylinder.

Rear brakes sticking, ...1.check flexible pipe, 2.stuck wheel cylinder pistons,..3.compensator valve [rarely]..4.Brake fluid return valve at master cylinder.

That's like saying that your gas pedal is normal except for sticking.

Is your emergency brake fully disengaged?

Depending on how hot your drums have become, there's a good chance they are out of round and won't work right without being turned. The same place that turns drums, can diagnose and fix the problem.

put me in the caliper camp

First thing to check is the flex hose swollen on inside allowing fluid to pass under pressure going to the wheel cylinder but not return. Second item is plugged compensating port in the master cylinder, this is a tiny hole that allows some brake fluid to re enter the reservoir. Normally you may have up to 4 psi of fluid pressure on the wheel cylinders when not in use to keep the cups against the inside diameter of the wheel cylinder to prevent leakage and this is controlled by a small usually rubber one way valve in the master cyl. Due to the age I would take a serious look at the rear flex line. Of course I assume you already checked the parking brake cables for free movement.

I had a '58 VW bug in summer 1967, I was driving down the highway after about 6 miles at 55mph the brakes dragged enough I had to pull over, get a tow truck, at the garage they determined it was the master cylinder, it was replaced and I was back on the road.

You also need to be aware that some brake systems had parts that swelled up with the wrong type of brake fluid, as I recall brake fluid can also absorb moisture.

The master cylinder MAY not be relieving pressure in the rear brake system.

The rear backing plated MAY have grooves that do not allow the shoes to return to their normal "at rest" position.

The story of the brake hose is still an option.

Drive till the brakes start to drag. Stop the truck. and open a brake line on the master cylinder that leads to the rear wheels. This will be the smaller portion of the reservoir. If fluid squirts out the master is out of adjustment, or is defective.

I am assuming wcb3801 is OP because of his answers closely describing the issue, work and testing done so far. GA to bob c because those are my same thoughts. A couple of more things to check. I once worked on a truck that had a load compensation valve for the rear brakes. It was a rod connected between the frame and the axle that changes a valve on the axle to provide additional braking with load increase. That could give your symptom and it sounds like this failed before any work was done so I am also assuming any work you have done has not increased the problem or changed any symptoms. My experience with master cylinder failures has always been soft spongy feel of the pedal and poor to no braking. Not saying the master cylinder cannot be the failure, but low on my suspect list. Did you bleed out the lines to get the dirt fluid out? This being almost 20 years old there is lots of dirt in the system. Lastly, you haven't mentioned ABS as a candidate. Maybe it was still an option verses standard equipment but if it is on the truck that need to have consideration. Some places I read about pulling the ABS fuse just to check if it is interfering with normal operation but I do not know if that would allow fluid return if it is the root cause.

Possible causes : Collapsed flex line to rear brakes, Rusted and or bad wheel cylinder, weak or damaged return springs.. Have a great day all...

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bob c is on the job, I'm not needed here.

I can't see how a master cylinder problem would stop the rear brakes from releasing.

Non/pre ABS pickups have load proportioning valves that can play up.

1994 F150 has RABS (rear ABS)

The RABS valve might be the culprit, could be either electrical or hydraulic problem.

The RABS module is on the inside of the left side frame rail about level with where the drivers feet would be.

Just because you can't see it, doesn't mean it can't happen!

Definitely needs new return springs, now.

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In the brake booster there is a length adjustment on the push rod which actually pushes the piston in the master cylinder. if it is screwed out too far it will prevent the piston retracting far enough to release the pressure to the brakes - ie uncover the inlet from the reservoir.

I have had it happen!

This is one possible cause, along with corrosion in the slave cylinders, and others - consult a Brake system specialist.

The easy test for the elongated push rod in that design is to loosen up the nuts holding the master cylinder to the booster by two turns, and retest the vehicle. If the problem is gone, shorten the push rod by one turn and retest again. Shorten till success, and then another half a turn.