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FWIW, I'd also be suspecting that lower wheel cylinder. BTW, technically, isn't what you picture above a two-leading-shoe brake setup?
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drum brake symptom
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D
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Actually, we used to call that a "Lockheed" setup, with two anchors, but that was long ago.
This makes no sense.
If the flex hose goes to the lower w/cyl, which activates the shoe in the lower quadrant, which is the one that sticks, and a steel bridge line runs from the extra port in the lower w/cyl to the upper, which activates the upper quadrant shoe, which doesn't stick, yet the pressure bleeds out of the upper bleeder screw with a "poof!" that releases the lower shoe....
Looking at the springs, it seems there may be an issue also with springs, as the top (large) spring is an upper shoe retract that binds to the pivot end of the lower shoe (and almost zero leverage exerted to the lower shoe), while the lower (smaller) spring may not be retracting the lower w/cyl and shoe properly.
What does your owner's manual show you for spring placement?
BTW, as soon as I realized what it was we were talking about, I knew what it looked like.
I had a 219 for a while.
I was nevert happier when I got rid of that thing...well, maybe when the FIAT 600 went away.....
Dave
This makes no sense.
If the flex hose goes to the lower w/cyl, which activates the shoe in the lower quadrant, which is the one that sticks, and a steel bridge line runs from the extra port in the lower w/cyl to the upper, which activates the upper quadrant shoe, which doesn't stick, yet the pressure bleeds out of the upper bleeder screw with a "poof!" that releases the lower shoe....
Looking at the springs, it seems there may be an issue also with springs, as the top (large) spring is an upper shoe retract that binds to the pivot end of the lower shoe (and almost zero leverage exerted to the lower shoe), while the lower (smaller) spring may not be retracting the lower w/cyl and shoe properly.
What does your owner's manual show you for spring placement?
BTW, as soon as I realized what it was we were talking about, I knew what it looked like.
I had a 219 for a while.
I was nevert happier when I got rid of that thing...well, maybe when the FIAT 600 went away.....
Dave
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The 2:30pm EST update:
Despite the hurricane ... I went out and pulled that wheel off again.
Lower shoe still won't budge. Bled the nipple, got a few drips, but no pressure. Lower shoe remained tight and extended. Won't wobble up and down with a screwdriver, altho' the upper shoe does move the normal 1/8" or so.
EDIT: I did pound on the shoe with my fist a couple times, and it moved back in. Then the screwdriver click test worked fine. Pushed and released the brake pedal again, shoes moved out; upper shoe returned to rest, but lower remained extended.
To me, it doesn't seem the brake fluid lines are part of the equation. Even if there's no pressure when I open the bleeder, the lower shoe remains "out". Seems it's a mechanical issue: weak spring, corroded pivot, or bad cylinder.
Just for the heck of it, I did some online searching for replacement cylinders and rebuild kits. All the suppliers ask if I have "ATE 26 " or "ATE 28 " embossed on the cylinder. The 28 indicates 28.57, the metric equivalent to 1 1/8". The 26 indicates 26.98, equivalent to 1 1/16".
Heaven forbid anything would go according to plan. The upper cylinder shows "24P"; the lower cylinder shows "15P".
Would someone please send me an EASY button?
T.
Despite the hurricane ... I went out and pulled that wheel off again.
Lower shoe still won't budge. Bled the nipple, got a few drips, but no pressure. Lower shoe remained tight and extended. Won't wobble up and down with a screwdriver, altho' the upper shoe does move the normal 1/8" or so.
EDIT: I did pound on the shoe with my fist a couple times, and it moved back in. Then the screwdriver click test worked fine. Pushed and released the brake pedal again, shoes moved out; upper shoe returned to rest, but lower remained extended.
To me, it doesn't seem the brake fluid lines are part of the equation. Even if there's no pressure when I open the bleeder, the lower shoe remains "out". Seems it's a mechanical issue: weak spring, corroded pivot, or bad cylinder.
Just for the heck of it, I did some online searching for replacement cylinders and rebuild kits. All the suppliers ask if I have "ATE 26 " or "ATE 28 " embossed on the cylinder. The 28 indicates 28.57, the metric equivalent to 1 1/8". The 26 indicates 26.98, equivalent to 1 1/16".
Heaven forbid anything would go according to plan. The upper cylinder shows "24P"; the lower cylinder shows "15P".
Would someone please send me an EASY button?
T.
D
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Good Lord Almighty!
Well, from many years of doing old cars, I find the number is often a casting number.
Now, if they are asking specific on what is SUPPOSED to be there, they must know.
You may have to remnove the cylinder to find out what you really have.
Interesting you had pressure yesterday, and not today, and yesterday relieving pressure released brakes.
Looking with a dual-cylinder setup there is a problem inside the cylinder, or still, something blocking a port.
If it was my car, I'd pull both cylinders on that side, open them both (don't mix parts), and inspect.
Can you cause the piston to retract with a screwdriver tip?
Well, from many years of doing old cars, I find the number is often a casting number.
Now, if they are asking specific on what is SUPPOSED to be there, they must know.
You may have to remnove the cylinder to find out what you really have.
Interesting you had pressure yesterday, and not today, and yesterday relieving pressure released brakes.
Looking with a dual-cylinder setup there is a problem inside the cylinder, or still, something blocking a port.
If it was my car, I'd pull both cylinders on that side, open them both (don't mix parts), and inspect.
Can you cause the piston to retract with a screwdriver tip?
OP
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Between 1953 and 1961, Mercedes chose from three different size cylinders on the front brakes for these cars: 15/16", 1 1/16", and 1 1/8" - and not in that order.
I'm betting that the 24P is ATE's metric equivalent to 15/16". Actually, 24mm is very nearly exactly 15/16".
And I'm betting that the 15P is ATE's non-metric code for 15/16".
Fool that I am.
By the way, screwdriver tip *does* move the piston rod into the cylinder. Takes some effort, but it moves.
T.
I'm betting that the 24P is ATE's metric equivalent to 15/16". Actually, 24mm is very nearly exactly 15/16".
And I'm betting that the 15P is ATE's non-metric code for 15/16".
Fool that I am.
By the way, screwdriver tip *does* move the piston rod into the cylinder. Takes some effort, but it moves.
T.
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If it moves, then yes, cylinders may be wrong size or worn out, or debris may be clogging a port, but I still don't like the springs.
When you flex the springs sideways with a screwdriver, is the long skinny one noticeably easier to flex than the short fat one?
Might also help to look at the other side and see how it is arranged.
ALSO, corrosion on those aluminium shoes to the metal anchor is a problem.
BTDT on those.
Pull that shoe, inspect the pivot area, clean it out and lube (anti-seize works, but I always use SilGlide, a NAPA paster lubricant in a tube).
When you flex the springs sideways with a screwdriver, is the long skinny one noticeably easier to flex than the short fat one?
Might also help to look at the other side and see how it is arranged.
ALSO, corrosion on those aluminium shoes to the metal anchor is a problem.
BTDT on those.
Pull that shoe, inspect the pivot area, clean it out and lube (anti-seize works, but I always use SilGlide, a NAPA paster lubricant in a tube).
D
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I STILL keep thinking LBC.
It's gonna crop up from time to time.
Since the flow path of the fluid and what makes it lock or not lock makes no sense, I have to keep referring back to your pictures and thinking back to my 219.
Okay, there is a good chance it's mechanical, springs maybe, but pull that upper pivot (that the lower quadrant shoe fits into).
If, as removing it, the shoe tries to move into the lower w/cyl, you've got lock.
If not, once out, try moving the shoe out of the slot in the w/cyl, to see if the sides have corroded in place.
That may also indicate why the fluid goes "poof!" when you open the bleeder, if there is tension on the shoe from a locked pivot.
Maybe.
Dave
It's gonna crop up from time to time.
Since the flow path of the fluid and what makes it lock or not lock makes no sense, I have to keep referring back to your pictures and thinking back to my 219.
Okay, there is a good chance it's mechanical, springs maybe, but pull that upper pivot (that the lower quadrant shoe fits into).
If, as removing it, the shoe tries to move into the lower w/cyl, you've got lock.
If not, once out, try moving the shoe out of the slot in the w/cyl, to see if the sides have corroded in place.
That may also indicate why the fluid goes "poof!" when you open the bleeder, if there is tension on the shoe from a locked pivot.
Maybe.
Dave
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I'm for pulling the lower slide pin, shoe and cylinder right off and going thru everything piece by piece. Be sure the pin is shouldered on the backing plate with proper distance between it and the shoe. Look for creative DPO stuff like spacing washers and suchlike, too! Clean the oval track in the center of the shoe VERY well on both sides and hone the cylinder bore clean.
Anti-seize on the surfaces of the shoe oval and pin where they make contact on reassembly helps but Dave's suggestion of the NAPA slider juice is better (anti-seize can "dry out" and it gets stiffer... think: heat).
And check the backing plate for a "ridge" where the shoe makes any contact.
Anti-seize on the surfaces of the shoe oval and pin where they make contact on reassembly helps but Dave's suggestion of the NAPA slider juice is better (anti-seize can "dry out" and it gets stiffer... think: heat).
And check the backing plate for a "ridge" where the shoe makes any contact.
OP
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I am IMPRESSED!
You guys must have these things implanted in your brains. Anyone who can remember that there's an oval self-adjuster slot in the shoe - wow!
(I polished both sides of that slot ... as there was a bit of a "lip" under the friction washer edge on the other shoe.)
About two months ago I had NAPA reline all the shoes and turn the drums. I cleaned every last part of the wheel brake carefully - but as the cylinders were relatively new and there were no signs of leaks, I didn't think of removing them and inspecting the innards. Stupid me. And when I pressed the piston stud with a pair of pliers, it moved, so I didn't give it much thought. Nor did I think of checking for crud in the lines between the two cylinders. It flowed clean when I bled the system, so I figured all was well.
Next week will be interesting, as I'll have time to work on the brakes again.
On a different tack, three months ago I started looking around for 185/80R13 tires. Finally about 3 weeks ago I found a supplier who located a set "down south". Tuesday he called and said they were in, and I went down to get them installed.
They were 15", not 13". Supplier said "my bad". I said something slightly different. Then I spent about six hours straight making phone calls. I hate making phone calls. Located four Kumho 185/80R13, went to actually touch them ("trust but verify"), said Hallelujah, paid cash, and put them in my Mazda's trunk. Onward through the fog.
T.
You guys must have these things implanted in your brains. Anyone who can remember that there's an oval self-adjuster slot in the shoe - wow!
(I polished both sides of that slot ... as there was a bit of a "lip" under the friction washer edge on the other shoe.)
About two months ago I had NAPA reline all the shoes and turn the drums. I cleaned every last part of the wheel brake carefully - but as the cylinders were relatively new and there were no signs of leaks, I didn't think of removing them and inspecting the innards. Stupid me. And when I pressed the piston stud with a pair of pliers, it moved, so I didn't give it much thought. Nor did I think of checking for crud in the lines between the two cylinders. It flowed clean when I bled the system, so I figured all was well.
Next week will be interesting, as I'll have time to work on the brakes again.
On a different tack, three months ago I started looking around for 185/80R13 tires. Finally about 3 weeks ago I found a supplier who located a set "down south". Tuesday he called and said they were in, and I went down to get them installed.
They were 15", not 13". Supplier said "my bad". I said something slightly different. Then I spent about six hours straight making phone calls. I hate making phone calls. Located four Kumho 185/80R13, went to actually touch them ("trust but verify"), said Hallelujah, paid cash, and put them in my Mazda's trunk. Onward through the fog.
T.
D
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It's like breaking your leg.
You never forget how painful it is.
You never forget how painful it is.
D
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Those oval holes are for shoe alignment, if I remember.
Like the Doc said, look for shims...shouldn't be any in there, the shoes should free float.
If you have a lot of corrosion on them, glass-beading of the holes used to work for me before using SilGlide.
Wire wheel on the steel pin.
Like the Doc said, look for shims...shouldn't be any in there, the shoes should free float.
If you have a lot of corrosion on them, glass-beading of the holes used to work for me before using SilGlide.
Wire wheel on the steel pin.
OP
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The oval hole is for the automatic adjuster. Friction washers hold the adjuster in place, but they do allow brake pressure to slide the shoe outward as the lining wears. My adjuster is completely tightened down per spec; no way could I push the adjuster out (or in) with just a slam of my fist, believe me.
It's the oval hole in the shoe itself, #6 on the diagram:
Not sure I understand what you mean by the "free float" thing tho'.
T.
It's the oval hole in the shoe itself, #6 on the diagram:
Not sure I understand what you mean by the "free float" thing tho'.
T.
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The shoe should easily 'float' thru the range the oval hole allows when the cylinder and return spring are off the backing plate. Are your felts (#11) in there?
#600 wet-or-dry is what I've used on the faces of the pin hole. You checked the backing plate for a ridge, yes?
And it is kinda-sorta like Dodge of th' mid '50's. Did one of those a while ago, NAPA actually listed and GOT the booster for us. I was impressed (with NAPA, not th' Dodge :wink: ).
#600 wet-or-dry is what I've used on the faces of the pin hole. You checked the backing plate for a ridge, yes?
And it is kinda-sorta like Dodge of th' mid '50's. Did one of those a while ago, NAPA actually listed and GOT the booster for us. I was impressed (with NAPA, not th' Dodge :wink: ).
D
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I mentioned the cocked piston six pages ago.
The free float is the pivot end of the shoe.
If the adjusters aren't dragging, check that pivot!
With aluminium shoes, heat, old brake fluid, road salts, dog pee, anything gets in there, corrodes.
Sometimes sanding will just shine the corrosion, and leave the part thicker than it should be.
You have a questionable area, scrape it with the flat edge of a knife.
If the glazed corrosion pops off in chunks, you've got some cleaning to do.
The adjusters......maybe some corrosion on the aluminium under those friction pieces.....and look at 18.
The upper and lower springs are the same number.
Look at your photo.
They are not.
The pin (32) fits into a socket in the shoe.
I had to almost beat one out on the 219.
It created all sorts of strange things....when you put the brakes on, the shoe moved out arcing around the pivot at the other end, and moved the end of the stuck rod (32) towards the outer edge of the w/cyl, jamming the piston.
Fun.
The free float is the pivot end of the shoe.
If the adjusters aren't dragging, check that pivot!
With aluminium shoes, heat, old brake fluid, road salts, dog pee, anything gets in there, corrodes.
Sometimes sanding will just shine the corrosion, and leave the part thicker than it should be.
You have a questionable area, scrape it with the flat edge of a knife.
If the glazed corrosion pops off in chunks, you've got some cleaning to do.
The adjusters......maybe some corrosion on the aluminium under those friction pieces.....and look at 18.
The upper and lower springs are the same number.
Look at your photo.
They are not.
The pin (32) fits into a socket in the shoe.
I had to almost beat one out on the 219.
It created all sorts of strange things....when you put the brakes on, the shoe moved out arcing around the pivot at the other end, and moved the end of the stuck rod (32) towards the outer edge of the w/cyl, jamming the piston.
Fun.
D
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I thought about that some more...
We didn't almost beat that pin out....we destroyed it and almost the shoe, but not quite.
At the time, parts were...interesting to find, so we removed the opposing pin (32) and made one out of steel rod, same length, I remember rounding the end with a file.....
We didn't almost beat that pin out....we destroyed it and almost the shoe, but not quite.
At the time, parts were...interesting to find, so we removed the opposing pin (32) and made one out of steel rod, same length, I remember rounding the end with a file.....
OP
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Thanks again gents.
First off, that picture of the brake isn't mine; it's a "brakes for dummies" picture from the MB Ponton website (mbzponton.org). My springs are equal, and have the same resistance and tension as the springs on the other front wheel.
Doc, when you say "felts", #11, I assume you mean the friction washers. Those are new.
I'm thinking that next week I'll pull the problem shoe's cylinder, check it and maybe ream it. If it still looks/works dodgy, I'll replace the entire cylinder if I can't find a rebuild kit. I've found kits at NAPA (Raybestos) for 1 1/16" and 1 1/8", but can't find them (yet) for the 15/16" cylinder that I have.
I've never checked a brake cylinder before (yeah, I know, I can hear you all laughing your heads off ...). If I first remove the shoe and just pull/push that piston rod, how far should it easily move in/out? Like 1/8", or 1/2", or 1.5", or ...? If it should move 1.5", and it only moves 1/2", then I'll know I've got a problem inside.
Tom
First off, that picture of the brake isn't mine; it's a "brakes for dummies" picture from the MB Ponton website (mbzponton.org). My springs are equal, and have the same resistance and tension as the springs on the other front wheel.
Doc, when you say "felts", #11, I assume you mean the friction washers. Those are new.
I'm thinking that next week I'll pull the problem shoe's cylinder, check it and maybe ream it. If it still looks/works dodgy, I'll replace the entire cylinder if I can't find a rebuild kit. I've found kits at NAPA (Raybestos) for 1 1/16" and 1 1/8", but can't find them (yet) for the 15/16" cylinder that I have.
I've never checked a brake cylinder before (yeah, I know, I can hear you all laughing your heads off ...). If I first remove the shoe and just pull/push that piston rod, how far should it easily move in/out? Like 1/8", or 1/2", or 1.5", or ...? If it should move 1.5", and it only moves 1/2", then I'll know I've got a problem inside.
Tom