Brake woes

franklin2

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My thought is to try bleeding the MC really well. I've done a poor job bleeding the MC before install and had a heck of a time getting brakes on some vehicles.

If you use the plastic plugs they give you with the MC, put it in a vise and slowly press the plunger in and out until you can't move the plunger at all, it's bled. I have had to pump some of them over 30 times to get all the air out of them.
 

The_Josh_Bear

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My thought is to try bleeding the MC really well. I've done a poor job bleeding the MC before install and had a heck of a time getting brakes on some vehicles.

If you use the plastic plugs they give you with the MC, put it in a vise and slowly press the plunger in and out until you can't move the plunger at all, it's bled. I have had to pump some of them over 30 times to get all the air out of them.

Agreed. I used the plugs and got no leaks and no air bubbles then did prolly 15 more strokes to satisfy myself. Never got zero movement but around 1/8" which is what the included directions say. I worked slowly too just in case. MC was nice and level in my vice.

It's looking more and more like a bad original MC followed by a bad new one out of the box. Wish I could find a way to plug the darn thing to eliminate the rest of the brake system.
 

IDIBRONCO

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There's a neat tool made just for bench bleeding a MC. Basically, it's a syringe with a tapered rubber plug on the end. You fill the MC reservoir(s) first. Then you stick the end of the syringe in the brake fluid and draw some into the syringe. Make sure that there's no air in side and hold the rubber part over the place where the brake lines attach. Push the brake fluid slowly in through that port and you're reverse bleeding the MC. It usually only takes 3-5 times to stop seeing bubbles come up through the brake fluid. I'll try to remember to find it and take a picture or two. This is why I say that I can swap out a MC in about 20 minutes (or less) using hand tools.
 

The_Josh_Bear

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SOLVED! New MC from Orielly's cause I bought the only one at my local NAPA two days ago. Bench bled, installed, worked. Bam done.

Rears are still touchy, maybe they got a few drops of something on them when I did axle seals, grrrrrr. $75 NAPA shoes down the drain. I got some cheapy Orielly shoes to test out for that problem later.

And I'ma take Wes's advice and get some nicer fronts to match, these ones started ok but never good. I read up on pad choices and besides StopTech, Hawk seems to make excellent pads, rated even higher for bite and longevity than StopTech. Any advice there? They cost more too.


There's a neat tool made just for bench bleeding a MC. Basically, it's a syringe with a tapered rubber plug on the end. You fill the MC reservoir(s) first. Then you stick the end of the syringe in the brake fluid and draw some into the syringe. Make sure that there's no air in side and hold the rubber part over the place where the brake lines attach. Push the brake fluid slowly in through that port and you're reverse bleeding the MC. It usually only takes 3-5 times to stop seeing bubbles come up through the brake fluid. I'll try to remember to find it and take a picture or two. This is why I say that I can swap out a MC in about 20 minutes (or less) using hand tools.
Funny thing you mention this, I saw that exact thing on youtube and ended up making one with a 10ml syringe my wife had from work. It was awesome! Worked very well-- except to satisfy my own curiosity I went back pumped it on the bench with the plugs in and still got a good amount of air out. Could have been my technique with the syringe but it was much more fun than the normal method and at least gets you 90% there in a few mins.

Thanks guys!
 

IDIBRONCO

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Funny thing you mention this, I saw that exact thing on youtube and ended up making one with a 10ml syringe my wife had from work. It was awesome! Worked very well-- except to satisfy my own curiosity I went back pumped it on the bench with the plugs in and still got a good amount of air out. Could have been my technique with the syringe but it was much more fun than the normal method and at least gets you 90% there in a few mins.

Thanks guys!
I've never had any issues with air in the MC after using this tool.
 

IDIBRONCO

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Here's the tool I was talking about. Sorry that it's blurry. My old fashioned camera doesn't take close up pictures very well. You can still get the idea though.

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The_Josh_Bear

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Yep that's basically what I made myself, worked well. I just used a grommet that happened to fit fine so it may deteriorate as it's just rubber. Way easier than the normal bench bleeding.
 

The_Josh_Bear

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So I finally got those Hawk front pads in, and man those things stop great. Much better than the previous house-brand pads.

BUT, the rears are still too grabby. They would be perfect if I had a heavy trailer hooked up or 1,500lbs in the bed.

Can the rear brake proportioning valves fail without leaking, or possibly get a piece of dirt stuck in them keeping them open?? I didn't take mine apart when I did the switch cause I wasn't thinking about it at the time. By the way I never thought I would say the "rear brakes are too strong" on one of these pickups! lol

Here's a link to the part I'm talking about, it plugs into the master cylinder between the MC and rear brake line:
https://www.ebay.com/p/1022097532?i...qNytzfQXUgVi-xvn2ebRdKbwQEEZJzgxoCa_UQAvD_BwE

As I understand things, this little device limits the maximum pressure allowed to the rear brake cylinders. (which disqualifies it from being a "proportioning" anything but whatever)
Idea 1: If that thing failed to operate I would be getting far too much juice to the rears, might explain things. But I don't know how they work or if it's possible for them to fail "open". And I'm allergic to throwing parts at problems!
Idea 2: I already have a cheap pair of shoes from Orielly I could swap in, which is annoying but doable. I was hoping to return those but $30 won't change my life one way or the other...
 

Thewespaul

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I could totally see a piece from a previously failed master cylinder causing an issue with the pv. You can take them apart and clean them, I always do that when I replace master cylinders, ultrasonic cleaner works well.
 

hacked89

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Since you want to diagnose and you said you arent familiar with pv, here's the logic to think about. Brake fluid flows from master cylinder through one side of proportioning valve, theres little valve and spring, it will always be open until X amount of pressure is built, then the valve starts to close until fully closed when panic braking. This is a generalization of the concept I havent taken that specific valve apart.
Now when they fail, if that valve isnt closing you can lock up the brakes with medium braking.
How exactly light or hard are you pushing the pedal when it locks up?
If you lift the axle off the ground can you spin the back wheel freely that drags?
The concept also assumes that the shoes arent touching the drums but the calipers are just touching the discs to work correctly.

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The_Josh_Bear

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I could totally see a piece from a previously failed master cylinder causing an issue with the pv. You can take them apart and clean them, I always do that when I replace master cylinders, ultrasonic cleaner works well.
Thanks Wes, I don't have an ultrasonic... can I shake it around gently in a jar of gasoline or mineral spirits, etc?
 

The_Josh_Bear

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Since you want to diagnose and you said you arent familiar with pv, here's the logic to think about. Brake fluid flows from master cylinder through one side of proportioning valve, theres little valve and spring, it will always be open until X amount of pressure is built, then the valve starts to close until fully closed when panic braking. This is a generalization of the concept I havent taken that specific valve apart.
Now when they fail, if that valve isnt closing you can lock up the brakes with medium braking.

1. How exactly light or hard are you pushing the pedal when it locks up?

2. If you lift the axle off the ground can you spin the back wheel freely that drags?

3. The concept also assumes that the shoes arent touching the drums but the calipers are just touching the discs to work correctly.

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That's also the concept that I believed to be true based on a little research.

The backstory is that without messing with the brakes at all my rears started to lock up on wet pavement under totally normal braking. Within a day they locked up under nearly ANY braking, even on dry pavement. Then I changed a bunch of things that needed changing anyways, bled the heck out of it, got new grabbier front pads, and here I am. (rear shoes are new and adjusted properly, had to get new ones cause my axle seals leaked and ruined the old shoes. Got scottseals and new shoes)

1. Currently on dry pavement I have to brake very firmly to get the rear wheels to feel/hear the rears braking too hard. I can feel the initial slowdown from them then hear the tires start to squeak a bit which means they are way too tight for the wet stuff. And it rains a LOT out here. (I haven't taken them out in the wet but I would guess one or both rears would lock up at an medium-speed braking situation. So like a stop sign at the bottom of a short steep hill or when someone suddenly decides to cut you off doing 10mph slower than you are, etc. )

2. The wheel that drags changes so it's not related to one side. I also have a Detroit locker in the rear axle which makes brake diagnosis a PITA, as it turns out. I take the wheels off now and adjust the shoes until I can't slide the drum back on, then loosen them up a tad so I can slide them on. (I've tried loosening them up more and more to add play and see if that helps but it doesn't really. There's just simply too much pressure in the line or something else I haven't figured out.)

3. Discs work great now and drums also slide right on and off with the parking brake off. Also the parking brake works perfectly and is strong, another indication that the drums are properly setup.
 

Macrobb

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BTW, if you have oil contamination in your rear brake shoes, they are /less/ likely to grab, because the oil acts as, well, a lubricant.


One idea is that perhaps the rear brakes aren't adjusted properly. Make sure to adjust the star wheel out as far as you can(pumping the brakes a couple times to even stuff up), then back in until it stops dragging. I've been told that you can get grabby brakes if they aren't adjusted properly.
 

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