drum brakes..

[skyline084]

This is a honda accord..
I changed the rear drum brake and now I cannot get pressure.
The fluid was low in the reservoir at one point, but not below the outputs.
I've bled the lines and it will be stiff, but then i start the car and lose the pressure.
I popped the drum off the brakes to see if they work and they do.. I pressed the pedal too hard which popped the cylinder.. I placed it back in though.. doesn't look damaged.
Why am I losing pressure?
Why would the master cylinder go bad from me taking pressure off it?
All I did was change the drum assembly, and after I changed it and didn't work, I changed it back. And still doesn't work..
I'm using a vacuum type bleeding kit so I can bleed them myself...
Any advice anyone?

[nissangirl74]

Find a friend and try bleeding them the old fashioned way. I'm betting you have air trapped in the line somewhere. FWIW, how old is the master cylinder?

[skyline084]

i did it that way too..which is why i'm kinda confused now.
Had her pump the brakes until there were no more bubbles..
Now I'm convinced there's air in the master cylinder some how.. gonna bleed that, than bleed the entire system with fresh fluid.. see what happens.

[themadscientist]

Use new fluid and you should be able to see a color change when the last of the old stuff runs out.

The fact that it "loses pressure" when you start the car could be because when you start the car the vacuum booster adds significant power to your pushing of the pedal. It may feel great when it's just your leg pushing the pedal, but the addition of the booster reveals it's not as great as you first thought. It could be air still in the system or waterlogged fluid. Brake fluid loses its quality and ability to do its job when it absorbs water and the exposed master cylinder would have left it vulnerable. Change all the old fluid.

[Bubba1]

Use new fluid and you should be able to see a color change when the last of the old stuff runs out.

The fact that it "loses pressure" when you start the car could be because when you start the car the vacuum booster adds significant power to your pushing of the pedal. It may feel great when it's just your leg pushing the pedal, but the addition of the booster reveals it's not as great as you first thought. It could be air still in the system or waterlogged fluid. Brake fluid loses its quality and ability to do its job when it absorbs water and the exposed master cylinder would have left it vulnerable. Change all the old fluid.

+1 about using fresh fluid, especially if the old fluid more than a year old.

[Dattebayo]

I pressed the pedal too hard which popped the cylinder.. I placed it back in though.. doesn't look damaged.

Did everyone miss this?

It's possible you have a damaged wheel cylinder now.

[skyline084]

i'm gonna try changing the fluid, it does look horrible. it doesn't matter if the emergency brakes hooked up, correct?
The wheel cylinder is fine.. It popped out, but I put it back in it's place and through the hub on and hit the brakes until it set it's self again.

[Red coupe]

i did it that way too..which is why i'm kinda confused now.
Had her pump the brakes until there were no more bubbles..
Now I'm convinced there's air in the master cylinder some how.. gonna bleed that, than bleed the entire system with fresh fluid.. see what happens.

She wasn't pumping the brakes with the bleeder open was she? It almost sounds like you just opened the bleeder then had her pump till air bubbles stopped coming out?

[skyline084]

nope closed while pumping, opened while holding and close quickly..
Now, I used a vacuum bleeder and started with the rear right tire until fresh fluid got into the canister. Still had bubbles..
Just went out and bought a new master cylinder.
Starting to bleed it now.

[skyline084]

do you have to bleed the master cylinder before hooking it up to the brake lines? I forgot to and started bleeding them already..
should i disconnect the lines and bleed this thing?
(I'm using a vacuum bleeder)

[4cefed]

If you aren't careful while bleeding and fully stroke the brake pedal, you can ruin the master. If the car goes for years without being flushed in the brake system, bits of crud and dirt can build up at the end of the normal stroke in the master cylinder. When you have to bleed the system and put the pedal to the floor, the seals in the master run over this ring of built up crap and can be damaged.

But, if you are using a vacuum system to bleed and are still getting bubbles, then I think you have air intrusion somewhere. Are positive the other bleeders are fully closed? Any wet spots in the lines? The slave that came apart could be leaking air in, slaves are cheap, I would change it out.

[MinisterofDOOM]

I despise drum brakes. I hate working on them, I hate that cars still come with them, and I hate their vulnerability to wet weather, especially after being parked. Their single positive feature is that the drums themselves last forever, assuming you don't let your girlfriend glaze them over by leaving the park brake on.

[skyline084]

leaves the parking brake on lol
I bench bled the master cylinder... there was really no air in it since i already started bleeding the brakes with it installed. I hooked it up onto the car, again.
Bled the brakes until all fluid was fresh. Still getting massive amounts of bubbles in the lines.
I can see the drum cylinder being a problem, which is the rear left tire. Aren't the rear left and front right on the same lines.. so wouldn't that mean only those two would be getting air consistently..?
It's happening to each line.
I don't see any wet lines anywhere, and I don't see why there should be.. Only reason i changed the one drum was to replace suspension assembly, so I don't see how all this s*** could go wrong just by removing and replacing a drum.

[skyline084]

When bleeding the master cylinder, is fluid suppose to be drawn back in once you release the cylinder? (piece that goes into brake booster)
I got two hoses running back into the MC fluid container.
I feel I got a bad MC out of the box.. I push the cylinder in with a screwdriver, fluid dumps into the container, but when i release the cylinder, fluid draws back through the lines in the reverse direction...

[Red coupe]

That is fine, no one way valve... The master needs to suck the fluid back up anyways, otherwise the brakes would never release and eventually you couldn't even push the pedal down (fluid in the calipers aint going no where but back into master...)

Done a little bit of bench bleeding... I had to make my own tool, so for better or worse here was my method, I'll include brake bleeding just cause:

I grabbed a few clear tubes like we used for normal bleeds, and strapped them all together to make less of a mess. I ran lines from the fluid out back into the reservoir.

Like you said when you pump it will pull fluid back in on the out stroke. When you push in try to hold, let the air bubbles start floating up toward the reservoir, then fold/kink/clamp the hoses so that fresh, air free fluid is pulled in from the reservoir. (I wait for the bubbles to rise a bit before clamping so that the tiny bit of fluid that DOES get sucked back into the master from the tubes is hopefully air free.

Once you stop getting air bubbles there, give it a good couple three more goes for the hell of it.

Once satisfied that that is good, re-install on the car and prepare to bleed. I know the vacuum/pressure/speed bleeders are cool, but I have never used ANYTHING better then two, loud, well rehearsed people. While bleeding is simple, it requires good communication to be fast and effect, It is important to be loud and to know what each other is doing.

If your brake system is stock, look up the recommended bleeding order. If changes are made or if you cannot find one start looking at the lines and how they are ran, bleed from the wheel with the longest run of line going to it, and work your way to the shortest.

Have the man on the wheel yell "PUMP"
This is the person in the cockpit's signal to begin slowly and smoothly pumping the brakes 4-5 times. When they begin to do this they should yell "PUMPING"

Once the brakes are pumped up, the person in the cockpit should yell "HOLD" to signify the brakes are under pressure, so the man on the wheel can open the bleeder.

Once the pedal hits the floor, cockpit should yell "FLOOR" while KEEPING THEIR FOOT DOWN, and waiting to be told either to pump again, or that they are "OK TO RELEASE". I typically go three times more then is needed.

Try following that strictly, maintain good communication so you can be sure no mistakes are made... If the problem is not fixed after that, you have bigger issues

[skyline084]

Thanks for the detailed response man.. but I've done literally everything you've said lol
I've had no problem bleeding brakes/clutches in the past, which is why this is confusing me so bad.
The only thing left that it could be is the wheel cylinder that popped when i didn't have the drum in place and hit the brakes... I simply re inserted it back into position and thought it would be fine.. It's not leaking or anything, but I think that piece is allowing air to come back into the system when I depress on the brake pedal. Only thing I can think of.
Gonna go pick one up tomorrow and see what happens so hopefully I'll be able to get to work in time lol

[Red coupe]

If its not leaking your probably fine... I really don't see air getting by but no fluid. I mean I guess air is smaller and can get through places fluids can't but yeah...no. Maybe if the piston isn't sliding back in smoothly, but I'll still go on record as saying no,
Hell, I've been wrong before though... Hopefully am again.
So you did manage to bench bleed with out just sucking the fluid and air right back into the same line every time you pumped yeah?

Considered simply getting another car? Would be easier...
:P

[Dattebayo]

The other thing is might be is the car needs to be on a level area, if it's on any kind of incline that would really hold some bubbles in.

[skyline084]

Haha get another car
It seems the thing is functioning perfectly fine, but there really isn't much more it could be and that's the only other part that I've messed with
As for bench bleeding, it was easy enough to get the bubbles out then i attached to car. The car is on a bit of an incline, i'll level it out tomorrow but that's not causing the amount of air I'm getting. This b**** is straight air running in the lines.

Best part about this whole thing, I only changed this b.c I needed to change out all the control arms/suspension with another assembly and thought it'd be easier to just disconnect the line and bleed them later instead of working around it. LOL guess not

[Dattebayo]

Perhaps the ends are cross threaded into the wheel cylinders or you broke a copper washer when you screwed them back in. Also, perhaps there was some debris between the washer and the sealing area on the wheel cylinder, too?

I broke a copper washer one time and it was the cause of a similar issue.

[skyline084]

I didn't even try to mess with the wheel cylinder anymore, went out and picked up a new cylinder.
Still cannot get pressure. wtf
Replaced wheel cylinder, Master cylinder, no leaks in the system.. don't get it.

[skyline084]

Brakes have pressure without vacuum. lose pressure with it. If I take vacuum off the booster, The fronts work but the rear drums don't. could the proportioning valve be messed up?