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Discussion Starter #1
Ok so I really didn't want to post this but here i am.

To start I have searched on line a bunch and have tried many different things but here i am still.

So i replaced rear brake lines from the splitting block on the frame rail ( proportioning valve ? )

ABS block is deleted

I also replaced all of the brake components ( shoes, hardware and drums ) and i had the drums turned while they were mounted onto the hubs.

I have the spongy pedal problem.

Problem is, I cant get these dang things to bleed.

I've tried, gravity bleeding, gravity bleeding into bottle, manually bleeding them and 2 different vacuum systems and i still cannot get a firm pedal.

To be clear the brakes were absolutely fine before the brakes were done.

I have gone through over half a gallon of brake fluid and still have a spongy pedal.

Anybody have any insight of something else i should look at?

Any input would be great.
 

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May be a long shot but did you adjust the shoes after you did the rear brakes?

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Discussion Starter #3
May be a long shot but did you adjust the shoes after you did the rear brakes?

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Yup sure did. I did double check just in case too. lol
 

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Discussion Starter #5
Did you drive it and seat/bed the brakes??

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no, its not road ready yet. Dont see how that would help a spongy pedal.
 

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Discussion Starter #7
If the pads/shoes aren't true to the drum/rotor...

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I have moved it around the driveway but thats about it.
 

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When you set your parking brake is sets firm and can hold the truck?
 

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Discussion Starter #9

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Discussion Starter #10
/Ok, so I worked on the brakes again earlier and found a few other things.

1) With the truck running, if I pump the pedal I can get a firm pedal but then quickly fades.

2) The rear drums were adjusted wicked tight and the truck wouldn't roll on a small hill.

3) would it make a difference if the front or rear of the truck is higher than the other while bleeding or should it be on level ground?

It seems to me that there is air in the system somewhere but I cant get any more air out of the bleeders. Could it be the proportional valve deal? Does something need ot be reset with it after not having any fluid run through it? Something i forgot to mention is that between the rear brake line being cut to re-plumbing it it was moved around the driveway quite a few times with only the front brakes and those didn't work worth a dang when doing so. With the engine off the pedal is a lot harder than while running but its still not as hard as before I did the rear brakes. Do i need to "bench bleed" the rear brake side of the master?

I'm hesitant to throw parts at it because it was perfectly functional before the rear brake line was cut and everything in the rear is new including the rubber line. On the other hand could it be a faulty wheel cylinder?

Thanks
 

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Describe that scenario again, pumping up the brakes? If you're pumping them up and then holding the pedal, and it's fading; that's a classic sign of a failed master or some other leak (visible) in the system.

Wheel cylinders either work, seize one or both pins, or leak...or give a spongy pedal if not bled like any other component. Mine were both seizing one pin and one was leaking. They gave me poor braking because the shoes weren't being moved by the wheel cylinders, but had little to do with pedal being spongy. The leaking one was obvious, the other looked fine but was in bad shape.

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Describe that scenario again, pumping up the brakes? If you're pumping them up and then holding the pedal, and it's fading; that's a classic sign of a failed master or some other leak (visible) in the system.

Wheel cylinders either work, seize one or both pins, or leak...or give a spongy pedal if not bled like any other component. Mine were both seizing one pin and one was leaking. They gave me poor braking because the shoes weren't being moved by the wheel cylinders, but had little to do with pedal being spongy. The leaking one was obvious, the other looked fine but was in bad shape.

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Failed master cylinder seems like it, fluid leaks past the piston and the pedal slowly drops down when pressed.
 

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Discussion Starter #13
Describe that scenario again, pumping up the brakes? If you're pumping them up and then holding the pedal, and it's fading; that's a classic sign of a failed master or some other leak (visible) in the system.

Wheel cylinders either work, seize one or both pins, or leak...or give a spongy pedal if not bled like any other component. Mine were both seizing one pin and one was leaking. They gave me poor braking because the shoes weren't being moved by the wheel cylinders, but had little to do with pedal being spongy. The leaking one was obvious, the other looked fine but was in bad shape.

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Failed master cylinder seems like it, fluid leaks past the piston and the pedal slowly drops down when pressed.
Update.

I installed a NEW not rebuilt master cylinder from NAPA and its still doing the same thing, While running pedal goes to the floor and if pumped will try to have a decent pedal but fades quickly to the floor. I'm fairly certain I have bled all the air out of the system because I cant get any more air bubbles out of the bleeders.

Could I assume the master is bad out of the box? Maybe I need to check if there are any leaks again. Could the proportional valve cause any of this? The brakes do work but im not sure how well on account of not being able to drive it on the road yet.

Is it critical to have the truck level while bleeding? My driveway is a slight incline and not sure if thats an issue or not. if needed I can park it in the yard where its mostly level and try bleeding it there.

I can also trade out the master cylinder for another and see if that makes a difference too.
 

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Update.



I installed a NEW not rebuilt master cylinder from NAPA and its still doing the same thing, While running pedal goes to the floor and if pumped will try to have a decent pedal but fades quickly to the floor. I'm fairly certain I have bled all the air out of the system because I cant get any more air bubbles out of the bleeders.



Could I assume the master is bad out of the box? Maybe I need to check if there are any leaks again. Could the proportional valve cause any of this? The brakes do work but im not sure how well on account of not being able to drive it on the road yet.



Is it critical to have the truck level while bleeding? My driveway is a slight incline and not sure if thats an issue or not. if needed I can park it in the yard where its mostly level and try bleeding it there.



I can also trade out the master cylinder for another and see if that makes a difference too.

I bled mine on a sloped driveway, mostly by gravity, then a couple shots with a vacuum bleeder...done.

It still indicates a bad master...for it to do that, it would need to be pushing fluid out somewhere...you're still pressurizing both sides of the proportioning valve, it's not like it goes in one side and back to the master.

Do you know for sure you wheel cylinders aren't leaking?

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Discussion Starter #15
I bled mine on a sloped driveway, mostly by gravity, then a couple shots with a vacuum bleeder...done.

It still indicates a bad master...for it to do that, it would need to be pushing fluid out somewhere...you're still pressurizing both sides of the proportioning valve, it's not like it goes in one side and back to the master.

Do you know for sure you wheel cylinders aren't leaking?

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I can not guarantee that they are not leaking BUT I am not loosing fluid out of the master when pumping up the pedal. The wheel cylinders are new but that doesnt mean they are good depending on how long they sat on a shelf in some warehouse. So this seems to be pointing to another bad master cylinder if everything else checks out.

Ill have to go through it again tomorrow or this weekend to rule out everything but the master cylinder.

Im getting sick of going through all this brake fluid. lol
 

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Update.

I installed a NEW not rebuilt master cylinder from NAPA and its still doing the same thing, While running pedal goes to the floor and if pumped will try to have a decent pedal but fades quickly to the floor. I'm fairly certain I have bled all the air out of the system because I cant get any more air bubbles out of the bleeders.

Could I assume the master is bad out of the box? Maybe I need to check if there are any leaks again. Could the proportional valve cause any of this? The brakes do work but im not sure how well on account of not being able to drive it on the road yet.

Is it critical to have the truck level while bleeding? My driveway is a slight incline and not sure if thats an issue or not. if needed I can park it in the yard where its mostly level and try bleeding it there.

I can also trade out the master cylinder for another and see if that makes a difference too.
If it is not leaking out anywhere, then it has to be leaking internally. When you bleed the brakes are you having a helper, as in someone pushes brake pedal and another person opens the bleeder on the brake cylinder? it should release fluid and the pedal drop, then you tighten the bleeder screw and other person lets up the brake pedal and you do it over and over till nothing but clean brake fluid comes out with every push of the pedal. And you start bleeding at the wheel furthest from the master cylinder.

But first your supposed to bleed the master cylinder to get out any air there, that may not be needed now.
 

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Discussion Starter #17
Update.

I installed a NEW not rebuilt master cylinder from NAPA and its still doing the same thing, While running pedal goes to the floor and if pumped will try to have a decent pedal but fades quickly to the floor. I'm fairly certain I have bled all the air out of the system because I cant get any more air bubbles out of the bleeders.

Could I assume the master is bad out of the box? Maybe I need to check if there are any leaks again. Could the proportional valve cause any of this? The brakes do work but im not sure how well on account of not being able to drive it on the road yet.

Is it critical to have the truck level while bleeding? My driveway is a slight incline and not sure if thats an issue or not. if needed I can park it in the yard where its mostly level and try bleeding it there.

I can also trade out the master cylinder for another and see if that makes a difference too.
If it is not leaking out anywhere, then it has to be leaking internally. When you bleed the brakes are you having a helper, as in someone pushes brake pedal and another person opens the bleeder on the brake cylinder? it should release fluid and the pedal drop, then you tighten the bleeder screw and other person lets up the brake pedal and you do it over and over till nothing but clean brake fluid comes out with every push of the pedal. And you start bleeding at the wheel furthest from the master cylinder.

But first your supposed to bleed the master cylinder to get out any air there, that may not be needed now.

Yes i have had a helper to bleed i also have tried gravity bleeding them.

I am going to order 2 more masters and another set of wheel cylinders to have for over the weekend when the parts stores are closed and just return what i dont use. I am also going to get some plugs so i can try to isolate where the issue is. Either master or somewhere else
 

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Even with air in the system, the pedal should stop at some point...it might be spongy, but is will still stop as the air is compressed. A pedal that drops slowly to the floor is classic signs of a leak in the system or bad master...as much fluid as you've done, bad wheel cylinders or calipers would have shown themselves as a leak.

Is the truck running when you are having this "fade"? If yes, could it be the vacuum building in the booster causing more assist? In other words, do you have a weak vacuum pump?



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Discussion Starter #19
Even with air in the system, the pedal should stop at some point...it might be spongy, but is will still stop as the air is compressed. A pedal that drops slowly to the floor is classic signs of a leak in the system or bad master...as much fluid as you've done, bad wheel cylinders or calipers would have shown themselves as a leak.

Is the truck running when you are having this "fade"? If yes, could it be the vacuum building in the booster causing more assist? In other words, do you have a weak vacuum pump?



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Truck os running when i have the fade. But i have to pump the pedal a bunch to have pressure then it fades away towards the floor. When the truck is off and i pump it it doesnt get rock hard like it should but it doesnt go to the floor like when running.

If the vacuum pump was bad wouldnt i have a hard pedal instead of a soft pedal?

Do you think that while i had the rear brake line cut and the pedal going to the floor to have anysort of brake messed anything up?
 

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Truck os running when i have the fade. But i have to pump the pedal a bunch to have pressure then it fades away towards the floor. When the truck is off and i pump it it doesnt get rock hard like it should but it doesnt go to the floor like when running.

If the vacuum pump was bad wouldnt i have a hard pedal instead of a soft pedal?

Do you think that while i had the rear brake line cut and the pedal going to the floor to have anysort of brake messed anything up?
What I'm thinking is that it has poor vacuum and that initial push bleeds off vacuum and the vacuum pump then "recovers" which translates into a slow build of vacuum and therefore a slow build in vacuum assist which then makes the brake pedal fade. When you pump the brakes, the vacuum is depleted and the brakes seem hard.

I just can't imagine that you have had bad master cylinders in a series or that you have a leak at this point (without seeing a puddle somewhere)...

Put a vacuum gauge on the vacuum system, see what you got (that would rule that out)...

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