rear disc conversion
First , I bought this truck from a barn sitting for five years.the trans an rear end needed rebuilding , which I did. while I had the rear end out I also did the disc mod on rear. after 4 months an everything back together, I don't get much fluid out of rear calipers. bleed repeatedly, got some better but not much (spongy pedal). so after reading a lot on here, I bypassed the RWAL an removed it. bleed again , still very spongy. since it was a very old MC and sat for 5 yrs I replaced it, with orellys reman(all that's available). minor improvement not much (very spongy). if you pump it 4 or 5 times rapidly you get a good half pedal, but leaks down. so is MC bad or combination valve? can I bypass combination valve altogether with 4 wheel disc? I have no idea how brakes worked prior to sitting up 5 yrs
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Did you replace booster?
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no, however I cant get a firm pedal even with eng off. so I,m thinking booster isn't in play. am I incorrect?
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1 Attachment(s)
Originally Posted by boeingguy
(Post 3282812)
First , I bought this truck from a barn sitting for five years.the trans an rear end needed rebuilding , which I did. while I had the rear end out I also did the disc mod on rear. after 4 months an everything back together, I don't get much fluid out of rear calipers. bleed repeatedly, got some better but not much (spongy pedal). so after reading a lot on here, I bypassed the RWAL an removed it. bleed again , still very spongy. since it was a very old MC and sat for 5 yrs I replaced it, with orellys reman(all that's available). minor improvement not much (very spongy). if you pump it 4 or 5 times rapidly you get a good half pedal, but leaks down. so is MC bad or combination valve? can I bypass combination valve altogether with 4 wheel disc? I have no idea how brakes worked prior to sitting up 5 yrs
If that is the case Try bleeding the front. You should only need to do one. This should center the piston in the valve. I ha a old chevy that was famous for doing the same thing.[laugh] |
ok I ,m heading out to give it a try thanks
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Bled again , I believe I got combo valve centered,I got a good pedal not running but same ol story once driving
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I think that you have a bad master cylinder. Unfortunately the state of re-manufactured MC's is weak at best. You may have to Keep trying until you get a good one...Mark
One other thing, did you use the calper with the E-brake? If so, make sure that you have the actuator arm indexed correctly, that is very important. It is also important to use the E-brake, that is how it stays adjusted... |
I think maybe bad MC too. yes i do have E brake and it is indexed and i do use it.
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MC on these trucks= Nasty can of worms.
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FWIW: I did the rear disc conversion on my mess using the Eldorado calipers with E-brake. With the stock/OEM MC, I felt the pedal stroke was too long so, . . . .
- I changed the master-cylinder to one from a 1983 Dodge B350 gasser. It has a cylinder diameter of 1.3125" where as our stock/OEM cylinder is 1.125". That will move more fluid with the same stroke length compared. (Had to narrow the new cylinder's mounting holes to fit our power booster). - Added a 10lb residual-pressure valve to the rear brake line. This reduces the amount of "Pump-Up required" if you will, with the rear calipers. Works like a champ! |
great info thank you
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Originally Posted by BC847
(Post 3283017)
FWIW: I did the rear disc conversion on my mess using the Eldorado calipers with E-brake. With the stock/OEM MC, I felt the pedal stroke was too long so, . . . .
- I changed the master-cylinder to one from a 1983 Dodge B350 gasser. It has a cylinder diameter of 1.3125" where as our stock/OEM cylinder is 1.125". That will move more fluid with the same stroke length compared. (Had to narrow the new cylinder's mounting holes to fit our power booster). - Added a 10lb residual-pressure valve to the rear brake line. This reduces the amount of "Pump-Up required" if you will, with the rear calipers. Works like a champ! |
If/when you get fed up with chasing obsolete master cylinders, booster, etc; I recommend switching to newer hydroboost/MC combo. :cool:
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Originally Posted by u2slow
(Post 3283080)
If/when you get fed up with chasing obsolete master cylinders, booster, etc; I recommend switching to newer hydroboost/MC combo. :cool:
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Originally Posted by mknittle
(Post 3283139)
A very worthwhile swap:thumbsup:
i would never ever do a rear disc conversion on these trucks, especially with those junk eldorado calipers. you're sacrificing pad surface and a good e-brake when switching to discs. 3" pads and 1 ton cylinders are great on the backs of these trucks when properly adjusted. |
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