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Discussion Starter · #21 ·

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Discussion Starter · #22 ·
I'm with dodge82273. I was going to say to look at the pushrod and m/c piston and how they relate to each other. The m/c pushrod might be too short. You should always use the same pushrod/master cylinder combo from the trucks you pillage from. Not all are the same.
Howdy
I measured the pushrod length very carefully when I put the new MC on it one. I later saw a cool simple tool that did the same thing. The master cylinder, booster, and proportioning valve that are on the truck now, all came off a truck that was ( bad motor) running and driving just a few weeks ago.
 

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any clearance between the pedal rod and the booster ? I'm just putting potential "problems" out there because it cannot be a mysterious thing . My experiences came back to bad masters , and stuck prop valves , but never has a "making a turn " problem unless the wheel bearings were loose as hell .
 

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Discussion Starter · #24 ·
So update today and progress. I got help and bled the brakes again, no air in the lines. Trucks been sitting at least a week, no leaks, drips or loss of fluid. The e-brake pedal in the cab has been rusted up for a long time before I got the truck. So I replaced the pedal and cable inside the cab with a good clean working pedal off the parts truck. Hooked that all up, tightened that up till the slack was out. Pressed the pedal and it goes about half way down and gets tight. I had the rear end off the ground already because I was going to tighten up the rear shoes. I grab the driver tire and it spins. The passenger doesn't. I had adjusted the rear shoes before and thought they were close, but obviously not. So some more adjusting, finally enough brake to get it on the road to actually bed the brakes with some hard stops, and a drive up my hill and the brakes work, they dropped a little but caught well before the bottom. I'm thinking someone went in and just fixed the passenger side rear brake sometime in the past, the wheel cylinder was good on that side and I bet they replaced the drum. The driver side wheel cylinder was bad and I bet that's the original drum. I'm guessing my hill is rough enough to to shake slack in shoes when I drove up it since the shoes were so far out of adjustment to start with. Pedal feels 100% better like it should. I'm going to adjust the driver side a little more tomorrow and I think it should be good. Thoughts?
 

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look close at the arm that operates the p brake inside the drum , they rust up , stick , and cause the wheel cylinder to have a "gap" between it and the shoes , makes the system act like the rear shoes are WAY loose out of adjustment even tho the shoes/drum are touching because that arm is holding the shoes out ......
 

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This. And before trying to readjust the shoes, back off the cables. They must be slack in order to get the shoes adjusted correctly.

Plenty of times I've seen people just crank up the cables without having the shoes properly set. All sorts of problems resulting.
 

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Discussion Starter · #27 ·
look close at the arm that operates the p brake inside the drum , they rust up , stick , and cause the wheel cylinder to have a "gap" between it and the shoes , makes the system act like the rear shoes are WAY loose out of adjustment even tho the shoes/drum are touching because that arm is holding the shoes out ......
When I redid the rear brakes, I took all that apart, wire brushed it on a bench grinder and stuck it all back together with never seize.
 

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Discussion Starter · #28 ·
This. And before trying to readjust the shoes, back off the cables. They must be slack in order to get the shoes adjusted correctly.

Plenty of times I've seen people just crank up the cables without having the shoes properly set. All sorts of problems resulting.
Will do, headed out now
 

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the spring OVER the p cable INSIDE the drum is what "returns" the p brake ARM in the drum , with cable loose it should return that arm freely .
 

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Discussion Starter · #30 ·
well, after a final adjustment and test driver, its worse. Real good brakes and then pedal just goes to the floor with no rhyme or reason.
3 different master cylinder, 2 new
2 different brake boosters , 1 new
3 different proportioning valves
all new soft lines
new pads, shoes, and wheel cylinder
no leaks, no fluid loss.
 

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O.K. pedal goes to floor without fluid loss means there is no fluid movement/ air or bypass by master . so , well the combo valve is SUPPOSE to stop flow to either the front OR rear when a line blows on that end allowing a LOW but serviceable pedal . ( brakes on good end only ) TO the floor means one of 2 things : either the combo valve was not centered , or is stuck . OR the master did not return all the way and has NOT pushed any fluid or it has defective cup seals .. when it does get a GOOD pedal , place both feet on pedal , press down hard , this is SUPPOSE to "center" the combo valve .

next option , after all this work , do you , can you , make steel brake lines ? some do / can some have never so I ask . If yes , what I would do is get a combo valve from a slightly newer truck , ( 92 up ) its aluminum and mounted on a bracket bolted on where the master is . make up the new lines , replace the steel combo valve thing under your feet , same function . Bleed the master , then gravity bleed the lines open 1 at a time , l/front .... this SHOULD keep the valve "centered" .

you are using 12 inch shoes in a 12 inch drum not 11's ? no offense , but I / we don't know what you know or don't know LOL

I suspect the master is not bled or not returning , or the combo valves on the rail suck . YOU are NOT alone , I have replaced 3 masters on 1 try to fix brakes "pulling my hair out " it was a bleeding problem , one end not bled enough , pedal OK then combo valve shifts , pedal bad . try to bleed BUT combo valve shifted can't bleed on end properly .. years later another truck bad combo valve drove me nuts even had a bleeder ball ( pressure bleed ) on that one ... take a deep breath and continue :)
 
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Discussion Starter · #32 ·
Update

The spring is over the parking brake cable, or at least it was in the pic I took before I pulled everything apart :) I am pretty good at putting things back together like they are in the pictures. Doesn't mean a previous owner didn't mess up though.

They are 12 inch shoes, didn't throw the old ones away yet.

So I started with the easiest, pushed the pedal real hard and started re-bleeding the brakes. Passenger rear went fine, no air. Driver rear pedal didn't feel the same, no air, so I stopped. Thinking it tripped the combo valve. Pushed the pedal real hard a few times and test drove. Same issue, random pedal to the floor.

Split the master and the booster, measured and there was a bit of a gap. Adjusted that and of course a little bit for good measure. Put the master back up, it seemed to fit flush with no issues (wrong), Bleed the master cylinder, hooked the lines up and gravity bled that.

Side note here, I was always under the impression that on the older heavy cast master cylinders, the front, larger chamber goes to the front brakes. Well on the 83 aluminum master cylinder with a plastic reservoir, the back line goes to the front brakes. Found that out when I swapped the master and combo valve.

So test drover the truck all over the place and on my hill several times, Great brakes never lost pressure Actually too good of a pedal. Seems the front brakes are not releasing all the way and dragging. So when thing cool down this evening I will split the master cylinder again and put some slack back in the brake rod.

Its a change and a easy fix and test drive. See what happens then.
 

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some slack needs to be there ....1/32 or more
 
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