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more brake problems


MattWalker

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The p15 has a new gas tank, fuel pump, pcv. system and is running better than ever.  Even added a redirad to listen to relicradio.  Been driving it everywhere with no problems.  Drove it out to stone mountain, had a great time until I noticed the brakes were getting way soft, almost to the floor. 

 

I did a minor adjustment(did a major one on fresh shoes and drums about 600 miles ago with Aamco tool) and after that, pedal was firm and high. Drove it another 100 or so, started getting lower again.  So two questions:

1. How often do you guys do minor adjustments?

2. Any chance those minor adjusters are slipping?

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Did you check the fluid?

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Had a similar issue with my P-12....I've found that bleeding this particular setup can be tricky, and air will often remain in the lines even when you think you've got it all. I'd try re-bleeding before anything else. 

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the minor adjustment would just be done with the upper bolt that is on the back of the backing plate or the halfmoon that moves the top of the shoe outward.

 

You have to remember that we do not have self adjusting brakes liek our modern cars. So as the shoes wear and then form to the arc of the drum you will have a greater distance tha thte shoes need to travel to make contact with the drum.

 

When you say soft pedal what happens when you pump the pedal when braking does it get harder and you get a firmer pedal?

 

Check the MC to see if you are low on Brake fluid also check and rebleed the air.  ALso put a block of wood on the floorbaord to prevent the brake pedal from going all the way to the floorboard when bleeding the brakes.

 

Look for any brake fluid on the backing plate to see if you have any leaks.

If you have a service or repair manaul consult that it sometimes list how often you should do a minot brake shoe Adjustment.

 

Just point to look at.

 

Rich HArtung

Desoto1939@aol.com

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If you have a hard pedal then 100 miles later it gets soft it sounds like moisture in the system. When you drive the car it heats up and expands into steam.

 

When you step on the pedal the steam just compresses and the shoes don't move enough. Suddenly the brakes get soft and very weak.

 

If it's just air in the lines without much moisture, the pedal would always be soft.

 

If it's just adjustment the pedal would always be firm and low.

 

It can always be a combination of the things though.

 

My suggestion is to back-bleed the brakes. This will usually force air and moisture out of the master cylinder all over the floor. A catch pan is suggested. ;)

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If you have a hard pedal then 100 miles later it gets soft it sounds like moisture in the system. When you drive the car it heats up and expands into steam.

 

When you step on the pedal the steam just compresses and the shoes don't move enough. Suddenly the brakes get soft and very weak.

 

If it's just air in the lines without much moisture, the pedal would always be soft.

 

If it's just adjustment the pedal would always be firm and low.

 

It can always be a combination of the things though.

 

My suggestion is to back-bleed the brakes. This will usually force air and moisture out of the master cylinder all over the floor. A catch pan is suggested. ;)

I am not following your logic with the steam. Water boils at 200 degrees. So you are stating that the each brake cylinder or a sigle cylinder or some line in the system has water init and when braking the system is heating up the lines to over 220 degree and causing the brake fluid or the water in the line to becom e steam.  I have a very hard time thinking that the brake lines and or the fluid and or water is really getting that hot to form steam.  I could see the brake drums getting hot and the shoes and lining but that is a great deal of heat.  Just think that then this car would boil over  oif there is that must heat being made from braking. With antifreese inthe rad that would be an awful amount of heat just by pushing on the brake pedal if could see heat building up if the pedal was sticking and then the shoes would start to smoke and you would get a burning smell .

 

Can you please explan how you came about your statement.  I might be wrong but I have a hard time understanding your popint of view.

 

Rich Hartung

Desoto1939@aol.com

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desoto1939, on 14 Nov 2014 - 2:52 PM, said:

I am not following your logic with the steam. Water boils at 200 degrees. So you are stating that the each brake cylinder or a sigle cylinder or some line in the system has water init and when braking the system is heating up the lines to over 220 degree and causing the brake fluid or the water in the line to becom e steam.  I have a very hard time thinking that the brake lines and or the fluid and or water is really getting that hot to form steam.  I could see the brake drums getting hot and the shoes and lining but that is a great deal of heat.  Just think that then this car would boil over  oif there is that must heat being made from braking. With antifreese inthe rad that would be an awful amount of heat just by pushing on the brake pedal if could see heat building up if the pedal was sticking and then the shoes would start to smoke and you would get a burning smell .

 

Can you please explan how you came about your statement.  I might be wrong but I have a hard time understanding your popint of view.

 

Rich Hartung

Desoto1939@aol.com

I am not defending Uly (as I don't necessarily agree with his statement and hope he will explain further) but I must ask if you can explain the highlighted portion of your posting above. I don't see a connection between the brake pedal and the engine cooling system.

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The engine is running and the internal temp of our engine get to be around 160-200. A rad will boil over at 220+ degrees. so I am having a hard time trying to figure how the brake fluid is getting to be over 220+ degress to create steam. especially when the brake lines are not in any way creating such heat as compare to the engine and water in the engine block and radiator.

 

If there was a steam build up then I would think that the steam would cause a major expansion and then the pistons would then be pushing out on all four wheels. Steam is a very powerful thing.  That I why I was using hte coolant in the radiator position.

 

Rich HArtung

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Brakes turn the energy of motion to the heat of friction.  The shoes and drums get very hot.  (Disks can be seen to be red hot, much hotter than 212 deg F.)  This heat may get back to the cylinders and lines. 

 

from Wikipedia for more discussion?

 

Characteristics of common braking fluids[1]   Dry boiling point Wet boiling point Viscosity limit Primary constituent DOT 2 190 °C (374 °F) 140 °C (284 °F)  ? Castor oil/alcohol DOT 3 205 °C (401 °F) 140 °C (284 °F) 1500 mm2/s Glycol Ether DOT 4 230 °C (446 °F) 155 °C (311 °F) 1800 mm2/s Glycol Ether/Borate Ester DOT 5 260 °C (500 °F) 180 °C (356 °F) 900 mm2/s Silicone DOT 5.1 260 °C (500 °F) 180 °C (356 °F) 900 mm2/s Glycol Ether/Borate Ester

 

 

DJ

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Brakes turn the energy of motion to the heat of friction.  The shoes and drums get very hot.  (Disks can be seen to be red hot, much hotter than 212 deg F.)  This heat may get back to the cylinders and lines. 

 

Seems you would have to ride the brake a lot to really feel the heat from friction as a problem. Normal driving and braking should not cause any such heat problem with any of it... Especially after you let off and get moving again. The friction heat should be gone.

Unless a shoe is dragging or a bearing is dry.

Edited by Lloyd
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And he's......gone never to return-brakes failed him and he crashed!

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Don't say that!

 

He said he "drove it out to Stone Mountain"...

 

I remember buying a used car for my daughter, and I warned her not to drive it in the mountains. She was unfamiliar with the car & I hadn't changed the brake fluid yet.

 

Sure enough she did it & she boiled the fluid & lost her brakes. She ran the car up on a stone wall that kept her from a very steep drop off The General's Highway.

 

:o

 

Heat from the shoes and drums is connected by a path of solid steel, right to the brake fluid. You think it's not gonna get hot? Boiling brake fluid is more common in humid climates though, because it's a function of water contamination. Here it's so dry it rarely happens, but that car probably hadn't had the fluid changed in over 10 years. 2 years is the recommended life of brake fluid.

 

If you have the master cyl under the floorboards and the cap gasket is missing, you can get a lot of moisture in the system. I'm not sure this is the problem--maybe his master cyl is weak/sticky, but I wouldn't discount the possibility until I'd bled out the system in a glass jar & checked for water.

 

I suppose his initial setup could be way off, so the shoes aren't making a good square contact. And thus rapid wear of the small surface that is making contact would require frequent adjustment. It is a bit tricky to set up these brakes. I made a simple gauge to do mine after seeing the photo of the official factory tool, and that makes it  a breeze.

Edited by Ulu
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The engine is running and the internal temp of our engine get to be around 160-200. A rad will boil over at 220+ degrees. so I am having a hard time trying to figure how the brake fluid is getting to be over 220+ degress to create steam. especially when the brake lines are not in any way creating such heat as compare to the engine and water in the engine block and radiator.

 

If there was a steam build up then I would think that the steam would cause a major expansion and then the pistons would then be pushing out on all four wheels. Steam is a very powerful thing.  That I why I was using hte coolant in the radiator position.

 

Rich HArtung

The steam can make the brakes drag, making more steam.

But the steam is compressible while brake fluid is not. That's why water in the system will cause the pedal to fade dramatically. When you push the pedal, the steam compresses and the fluid doesn't see full pedal pressure at all.

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Wow, this spurred a lot of discussion.  I think I used the wrong word, "soft".  The pedal is always firm but gets very very low.  So low once it touched the floor.  Then I adjust the minor adjusters and the pedal is high again.  The odd part it gets quite low over the course of only 100 miles or so.  I have the Aramco 1750 tool which I used when the shoes were new.  Every part on the brake system is new.  Cylinders, drums, shoes, springs, master cylinder, bearings, seals, hoses, lines....

The master is a 1 inch dual chamber which I initially thought was the issue but it seems to work well now.  It really seems like the minor adjusters are slipping but have not heard of that happening from anybody else.  Maybe the shoes are still arching?  Probably been about 600 miles on the shoes and drums. 

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. . . Maybe the shoes are still arching?  Probably been about 600 miles on the shoes and drums. 

Were the shoes arced to match the drums before you installed them? If not then you may have very little contact area which will reduce braking effectiveness and will cause rapid wear on the part of the shoe that is contacting resulting in the need for frequent adjustment.

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Where did you get the 1" dual chamber master? I recall reading something a while back about problems with dual chamber masters when using factory brake shoes.

 

I did a search and this was the comment I found.

 

 

Chester Brzostowski, on 03 Sept 2010 - 09:11 AM, said:

Don,

Just an FYI, I spoke with Ralf today and canceled the duel master setup. Apparently this setup will not work unless you put ECI’s disk break kit in your car. I wanted to keep the stock brakes and use the duel master for safety purposes only.., but there is no solution for this type of setup.

I hope you have better luck. Ralf got a little miffed when I told him that I would rather cancel the order then work on a solution in that I preferred to be the second recipient rather then the experimental first. He responded that if he designed it you could bet your life on it. Working with engineers all these years I choose to pass on the bet.

Good luck with your setup,

Chet…

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Well it doesn't sound like steam if it's not soft. I'd say adjust them a couple times to see if the shoes will bed in, or just take the brakes apart and see how well the shoes are really arced.

 

I've done a few brake jobs where a machine to arc the shoes wasn't available, and I arced them by hand, matching them to the individual drums, which were each turned slightly different diameters.

 

You don't get a perfect job by hand, but if you make a few hard stops without glazing things up, they will take a minor adjustment or two, then be fine after.

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I have seen on occasion the adjuster break lose from the bolt and not stay in adjustment. However I cannot see this happening to all 8 of them at once.

 

hmmm...I forget the exact mechanism of these. Are the adjusters "handed"? That is to say, Is it possible to put a left adjuster on the right side & vice versa?

 

I wonder now if there is an assembly error or maybe just an adjuster worn sloppy in its hole.

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The minor adjustors are built into the backing plates. They don't really come apart. Thats why I say its very unlikely more than one is broken and even that seems doubtful.

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As I recall, they're spring-loaded to the plates as well, so they really shouldn't have any funny wear from vibration.

 

I dunno....Unless there's physical damage (like the adjuster is tweaked or the backing plate is dinged in just the wrong spot, or a shoe isn't going fully into the slot) I think this either points to something getting loose, or rapid wear due to poor initial setup. Maybe something wasn't seated solidly at first.

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