Rep Power: 182

Hi,

I've finally bought a vacuum pump, this model http://www.mityvac.com/pages/products_hvpk.asp in particular. When I start to bleed the rear drum brakes with the vacuum pump, there's literally an infinite amount of bubbles coming out from the bleeder valve, there's much more air than fluid coming out. No matter how many times I bleed it, air just keeps coming out, but brake pedal just keeps feeling spongy no matter what.

In total, I've used 2 liters of brake fluid. 1 liter for flushing the old fluid out and 1 liter for bleeding air out of the system.

What is really bugging me is the fact that there is almost no air coming out of the system at all when using the traditional method, which is pumping the brakes.

The pedal still feels as spongy as it was before flushing and bleeding the system despite all that air coming out.

Anyone had this issue?

Thanks

 
Rep Power: 517

The air you see is entering the clear hose from around the threads of the bleeder screw. The vacuum is pulling it in. Normal.
Trust the traditional method if you are looking for air.


Low pedal or spongy?
Manually adjust the shoes.
Check for seized slides and pads on the front.

Is this a brand new problem, or has it been slowly getting worse?

 
Rep Power: 182

When we got the car last year, the brake pedal was really firm, but then we heard a noise in the rear passenger brake, we suspected something was wrong within the drum brake system, we took out the drum.

We then did what we weren't supposed to do: depress the brake pedal with the drum removed. The shoes were pushed out way too far and we couldn't put the drum back on. Instead of adjusting the shoes manually with a screw driver, we tried hitting the shoes with a hammer but the rubber seal around the cylinder slipped off due to the impact and that's when the pedal started feeling spongy. Air has entered the system.

Since then, we tried bleeding the system with the old fashioned way and not much air comes out and the pedal does not feel less spongy at all in any way.

Equipped now with a vacuum, I no longer know what to do.

You might be right about air getting through the bleeder valve thread.

The thing is, there doesn't seem to be air coming out, at least, a very little amount with the tradional way.

How long are you supposed to spend on bleeding brakes until there is no more air? How many rotations are you supposed to do?

By rotation I mean going through all brakes. DF PF PR DR
D stands for Driver, P for Passenger and F/R for Front/Rear.

That's the order recommended in Honda's manual based on what forums say.

We did adjust the shoes correctly, drum does not rotate freely by hand without applying brakes.

About the noise itself, we suspect it is a warped drum. The pedal pulsates when braking high speed. Definitely comes from the rear since steering wheel is not vibrating but handbrake does when using it at that speed. (actually the e-brake itself doesn't but vibration is felt through the car's body)

It's a problem that has been quite stable, not improving but not getting worse either. Just annoying not being able to restore the brake pedal's efficiency.

 
Rep Power: 517

we tried hitting the shoes with a hammer but the rubber seal around the cylinder due to the impact and that's when the pedal started feeling spongy. Air has entered the system.

OR you really hurt something.

OR there is too much mechanical travel in the brake mechanism.
Adjustments may not do anything if there is real damage.

What got replaced after damaging everything with the hammer? Wheel cylinder? Shoes? Springs?
If there are damaged parts, bleeding it is moot until it is fixed correctly.

Make sure the handbrake mechanism goes to the fully released position too, or else the manual adjustment will be incorrect.




Since then, we tried bleeding the system with the old fashioned way and not much air comes out and the pedal does not feel less spongy at all in any way.


I can isolate each brake from the system to see if removing one restores proper feel. Then I know where to be looking.

I could clamp off a flex-hose, or cap a line with a plug. I really hate clamping flex-hoses, they can be damaged in the process.

I could remove the shoes from one wheel and use a C clamp to keep the cylinder from exploding the pistons out. (Don't damage the rubber boots!!!)



Equipped now with a vacuum, I no longer know what to do.

Use the manual method if this confuses you.


You might be right about air getting through the bleeder valve thread.

Another thought: If you have damaged seals in the wheel cylinder, they could allow air to go past under a vacuum.


The thing is, there doesn't seem to be air coming out, at least, a very little amount.

Maybe it is not air that you are fighting.

Excessive mechanical clearances will require additional pedal (hydraulic) travel to compensate.


How long are you supposed to spend on bleeding brakes until there is no more air? How many rotations are you supposed to do?

By rotation I mean going through all brakes. DF PF PR DR
D stands for Driver, P for Passenger and F/R for Front/Rear.

That's the order recommended in Honda's manual based on what forums says.

Real world: The official Honda order is backwards form what I learned long ago that applied to every car in existence back then. But back then there was no such thing as ABS, and the majority of cars on the road still had 4 wheel drum brakes.

IMHO the KEY here is to use a consistent method that will address each wheel without fail. It is probably wise to do fronts first, since they are quickest to bleed out.

Real world: 6 complete strokes of the brake pedal should be plenty to get fresh fluid to move from the master cylinder to the rear wheel cylinders. (This assumes a system that was already working properly, not one that had air in it and NEEDED to be bled...i.e. if you cracked open a line at the master cylinder and got a single air bubble in it, 6 complete strokes should have that air bubble moved all the way through and expelled out of the wheel cylinder bleeder.)
This theory goes to hell if there is a lot of air in a system though, so 6 strokes cannot apply to all situations.

Real world: I do what *I* need.
If I already know where the air is, I go directly to that wheel. No need to go through the motions of bleeding 3 other wheels that I know aren't part of the problem.
If I replace a master cylinder and have to bleed brakes, I go to the closest, easiest fittings in the system. If the ABS pump is handy, I would do every bit of my bleeding there. I know there won't be air at any of the wheels in this case. Once I have proper feel, then I can worry about flushing the old brake fluid out, if necessary.
If I replace brake lines and I know every last bit of the system is empty, I will do as a book says and bleed around all 4 wheels systematically, several times if necessary. ...
However.....sometimes no amount of normal manual bleeding will get it. It might take alternate methods that aren't necessarily in the book. Knowledge of brake hydraulics, reason, logic, and experience come into play now.

Air bubbles can get trapped in the high spots of the brake lines. Vacuum causes the air bubble to get bigger (expand). Pressure makes bubbles smaller.
Sometimes vacuum bleeding can't be used, only pressure works.





About the noise itself, we suspect it is a warped drum. The pedal pulsates when braking high speed. Definitely comes from the rear since steering wheel is not vibrating but handbrake does when using it at that speed. (actually the e-brake itself doesn't but vibration is felt through the car's body)

You described the feel and actions of a warped drum.
What kind of noise could that make?

It's a problem that has been quite stable, not improving but not getting worse either. Just annoying not being able to restore the brake pedal's efficiency.


There has to be a logical reason, whether it is mechanical or hydraulic. Once it is figured out, it should make perfect sense.


HTH

 
Rep Power: 182

Oh hi ezone!
Didn't notice it was you until your last post.

What got replaced after damaging everything with the hammer? Wheel cylinder? Shoes? Springs?
If there are damaged parts, bleeding it is moot until it is fixed correctly.


Nothing has been replaced, we managed to put the rubber boot back on and the mechanism seems to be working properly. Since that day, braking efficiency hasn't decrease whatsoever, it's really just the pedal feel.

Oh and I forgot to say that when the rubber boot slipped off the cylinder, some brake fluid spilled every where, no much, but I believe it was well enough to let air enter the system. In a contained system, when something comes out, something comes in right? In this case, liquid and air.

Make sure the handbrake mechanism goes to the fully released position too, or else the manual adjustment will be incorrect.
Of course!

I also forgot to mention that only the rear passenger side cylinder/rubber boot was "damaged" (it does not seem to be). Rear driver drum brake was left untouched since the noise wasn't coming from there.


I can isolate each brake from the system to see if removing one restores proper feel. Then I know where to be looking.

What do you suggest I do?

Use the manual method if this confuses you.

It doesn't really confuse me, I thought this was a sure-to-work method but when I saw all these bubbles coming out from the rear on both side (now I know it could be because it is pulling air from the bleeding screw thread), I became kind of desperate.

Another thought: If you have damaged seals in the wheel cylinder, they could allow air to go past under a vacuum.

Rear driver side brake was left untouched, still, the "infinite amount of air"
coming out is the same as the rear passenger side.

Real world: 6 complete strokes of the brake pedal should be plenty to get fresh fluid to move from the master cylinder to the rear wheel cylinders.

By one complete stroke, do you mean depressing the brake pedal completely? When we flushed the old fluid, we did 10 complete strokes for each wheel. Air was coming out, but not that much. I thought it would be more than enough to flush all the air out at the same time, but then, pedal feel didn't change.

Real world: The official Honda order is backwards form what I learned long ago that applied to every car in existence back then. But back then there was no such thing as ABS, and the majority of cars on the road still had 4 wheel drum brakes.

I know, but it seems to be different with 7th Gen Civic. One thing, my car isn't ABS, so I guess it makes things simpler.

You described the feel and actions of a warped drum.
What kind of noise could that make?

Hmm, I'm not really good at describing noise. It's like something is hitting the drum while it is rotating. It's constant noise that varies with speed, the faster, the louder. Now that the pedal is spongy, I can apply less pressure in the brake system due to the longer pedal travel. Thus, that noise a lot less noticeable, but it is still felt a little bit through the car.

There has to be a logical reason, whether it is mechanical or hydraulic. Once it is figured out, it should make perfect sense.

I don't want to sound high and mighty, but I believe the noise and the pedal feel isn't related. The only link between them is the fact it's that the noise "made" me cause that spongy pedal feel.

The air you see is entering the clear hose from around the threads of the bleeder screw.
Do you think putting some grease around the thread would solve the problem? Bleeding with a vacuum pump isn't a 100% working method, but if I can make it work, why not. Pumping the brakes really is exhausting and cruel for the one doing it, especially when there is no guaranty that it will bring results.

As always, thank you ezone.

 
Rep Power: 517

Oh hi ezone!
Didn't notice it was you until your last post.

How can you miss one of my long, drawn out replies? LOL


Nothing has been replaced, we managed to put the rubber boot back on and the mechanism seems to be working properly. Since that day, braking efficiency hasn't decrease whatsoever, it's really just the pedal feel.

Have you had the drum machined yet?

Oh and I forgot to say that when the rubber boot slipped off the cylinder, some brake fluid spilled every where, no much, but I believe it was well enough to let air enter the system.

That's new...
Ok, let me see here----there are 4 rubber pieces on a wheel cylinder. 2 outer boots that mainly seal the innards from the environment, and 2 inner cups that actually have the job of containing the fluid and the pressure.
Air can be pulled past the cups with vacuum, then it would be trapped inside the wheel cylinder.
Use the traditional pedal pumping method.

You lost some fluid, so that has to mean one of the inner cups got dislodged at the very least.....

IF the shoes and hardware are perfect, then I'm thinking that one of the inner cups or the spring and expanders are screwed up.

You can probably buy wheel cylinders for under $25 if need be.






In a contained system, when something comes out, something comes in right? In this case, liquid and air.

Sure.
But-----as long as the master cylinder did not drain the fluid empty from one half of the reservoir and get air in it----most or all of the air would be in the line for only that wheel. You shouldn't have needed to bleed all the other lines out, and this would have been bled thoroughly in a few minutes. How long was it "open" and draining fluid out? If it went empty, you could be looking at bench bleeding the master.



I also forgot to mention that only the rear passenger side cylinder/rubber boot was "damaged" (it does not seem to be). Rear driver drum brake was left untouched since the noise wasn't coming from there.

Didn't screw up ALL of it huh? Only one side of it?

What do you suggest I do?

Drop back 40 and punt.

Oh. Wait....
This is what I meant: Clamp off the line with a smooth-jaw tool, like this:

Then pump the brake pedal and see if it is higher (or feels more correct).
Now figure out why.

This method only removes the single brake from the picture, so if pedal is restored, you know the problem must be in that brake SOMEwhere.

But you already know what wheel is causing the problem, right?



Another thought: If you have damaged seals in the wheel cylinder, they could allow air to go past under a vacuum.

Rear driver side brake was left untouched, still, the "infinite amount of air"
coming out is the same as the rear passenger side.

From above: Air can be pulled past the cups with vacuum, then it would be trapped inside the wheel cylinder.
Use the traditional pedal pumping method.



By one complete stroke, do you mean depressing the brake pedal completely?

Yeah.

Air was coming out, but not that much. I thought it would be more than enough to flush all the air out at the same time, but then, pedal feel didn't change.

Something is goin on. I can't tell what you are doing....
Damn, I can't SEE it from here.



Hmm, I'm not really good at describing noise.

Thunk thunk thunk with every wheel revolution....?




There has to be a logical reason, whether it is mechanical or hydraulic. Once it is figured out, it should make perfect sense.

I don't want to sound high and mighty, but I believe the noise and the pedal feel isn't related.

I was only talking about the pedal feel.




Do you think putting some grease around the thread would solve the problem?

I wouldn't do that.



Bleeding with a vacuum pump isn't a 100% working method, but if I can make it work, why not. Pumping the brakes really is exhausting and cruel for the one doing it, especially when there is no guaranty that it will bring results.


IMHO You have probably missed something major that is causing the low pedal. What it is, I cannot tell from here.
But I betting THIS has a lot to do with the problem: Once you figure it out, the bleeding should be quick and relatively painless.

Have you compared (visual) shoes and springs and links to the opposite side?

HTH