Soft Spongy Brake Pedal - Dodge Cummins Diesel Forum
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post #1 of 6 (permalink) Old 12-20-2009, 08:00 PM Thread Starter
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Soft Spongy Brake Pedal

Not sure if my sig. is updated......1993 W350 Cummins

3 months ago i had a brake problem. The right rear would lock up when i depressed the brake problem. I took the truck to my local mechanic and he replaced the rear shoes and a broken parking brake cable. This solved the problem but i ended up with a soft spongy pedal. I called the mechanic and he said that in a few weeks the rear brakes would adjust. Well they didnt and i took the truck back in...........a week later i got it back and they now replaced a "proportioning valve" and claimed the pedal is better. Well, its not!

Not sure what to do. I dont really wanna go back to the same mechanic. I bled the front but im not sure how to access the rears.............a local autozone told me that i need a new booster and might as well get a new master cylinder while im at it.

What do you guys think?

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post #2 of 6 (permalink) Old 12-20-2009, 09:20 PM
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A lot of 'sponginess' comes from the failure of one or both of the rear brake adjusters to work properly. I have replaced one of mine. The sharp, knife-like edge on the adjuster gets dull and just slides over the adjuster wheel without doing anything. When my brakes get feeling spongy and the pedal goes low, I adjust the one I have not yet replaced and the pedal becomes firm again. Sometimes too firm, if I have over-adjusted. I suspect that you could just remove and regrind the adjuster. Your problem is really common on these trucks because of the number of miles they rack up. If you don't want to bother tearing the brakes apart, buy a white paint marker pen and mark the backing plate with an arrow to indicate which direction you have to turn the adjuster. You will be adjusting them every three or four months and trying to guess which way they have to be turned is a major pain in the you know what. It takes a lot of turns to bring the brakes up properly and it is frustrating to keep on going and then discover you have been turning the adjuster the wrong way. Thanks for reminding me I need to change the adjuster mechanism on the other wheel. I must remember it when warm weather returns.

91 (08-90) D250
5sp 2wd 511k VE 'adjusted', 3200 spring, Pyro, boost, 3.54 ,:thumbsup KN, 1\8" timing bump, 25mpg city 30mpg hiway 20mpg towing 6k 5'er
R60/7, Volvo 245 GL 320 k km's, f150 4x4 5 spd, MPG's are in Imp gal's
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post #3 of 6 (permalink) Old 12-21-2009, 10:36 AM
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Your ABS hydraulic unit may be leaking into the accumulator also. When that happens, your pumping brake fluid against a spring loaded piston.
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post #4 of 6 (permalink) Old 12-21-2009, 12:21 PM Thread Starter
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how do i adjust the rear brakes? can it be done from the back side of the drum or do i have to take the drum off ? I have had the wheels off the back axle but never went any further. On my half ton pickup the drums just pop off but this 3/4 ton it looks like there is something that holds the drums on.
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post #5 of 6 (permalink) Old 12-21-2009, 05:29 PM
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Quote:
Originally Posted by Left out in the cold View Post
Your ABS hydraulic unit may be leaking into the accumulator also. When that happens, your pumping brake fluid against a spring loaded piston.
I have heard that you can take apart the ABS unit and clean it out. Has anyone tried this before?
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post #6 of 6 (permalink) Old 12-21-2009, 10:24 PM
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On the adjusting issue, like most drum brakes there is a slot in the back of the backing plate.

It is usually covered by a rubber plug. If you use a light you can usually see both the star adjuster wheel and the threaded part the adjuster uses to expand or contract the brake shoes. The only reason to pull the drum is to replace parts.

I know nothing about the abs business because my early production truck does not have abs.

91 (08-90) D250
5sp 2wd 511k VE 'adjusted', 3200 spring, Pyro, boost, 3.54 ,:thumbsup KN, 1\8" timing bump, 25mpg city 30mpg hiway 20mpg towing 6k 5'er
R60/7, Volvo 245 GL 320 k km's, f150 4x4 5 spd, MPG's are in Imp gal's
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