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Trouble building pressure on 1980 r model


Dieseldan77
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Got an air pressure issue on 1980 r model. It will build pressure up to about 60 psi and hover there. It's not enough to turn off buzzer and light. I have found if i throttle it up, it will build slowly as long as I got my foot on it. When i let off it will start dropping right away. As long as I keep my foot on it and get the psi up over 90, it will start building pressure like its supposed to and I can let off the throttle. Any thoughts and ideas would be welcome. Thanks.

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Deezel Dan

Gudday M8

a few things I have found with air n up

<1> the main pipe/hose from the compressor to the wet tank gets restricted

by a build up of crud - oil burnt like charcoal/tar in side the tube

<2> a crack or leak from said hose th@ cant B detected with engine run n

<3> compressor governor unload n.. if it is not lay n upright ovr time the inningz will wear with the help of gravity

my B replace compressor governor ..... they cheap n available @ all good cnr stores

jist my 2 cents worth tax FREE

LOL

cya

§wishy

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LIke Swishy said, unloader is not doing it's job. Repair is pretty straight forward.

If the problem has been getting worse over a period of time, compressor is just worn out. If it is original in a 1980, you got your moneys worth. Shop around, someone is bound to have your model on sale.

Jim

It doesn't cost anything to pay attention.

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air the tanks up with a compressor- engine off- first then check all hoses lines etc repair all found leaks then if it still won`t air up start buying parts one common cause for what you describe is worn or stuck one way check valve where main line enters primary tank

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The rubber/steel braided line after the lead off line may be bad, especially if its old or never been changed. A spray bottle of soapy water should tell you right away. Soak the lines from the air compressor discharge to wet tank or dryer. If the line(s) bubble up there is your problem.

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I agree with the guys sayin unloader (that is if they are referring to what I call a governor). I drove a truck with a triple 4 cummins years ago that would eat them. I pulled MI gravel trains with it (so mostly summers) and would replace it about twice a season. Carried one in the toolbox at all times. It would work fine one day, then, the next the same problem as yours. With eight axles and three places to wiggle behind you, not to mention the 150,000 plus pounds, the last problem you want is an issue with air. I say replace it, it isn't expensive and is very easy to change. I used to do it in the dark with a flashlight in about ten minutes.

:chili:Take care of your ride and it will take care of you :chili:

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I have read this post with interest for the past few days as my B model would only build about 80# but not hold. Found some leaking lines on removal of the cab. Thought I would replace the governor / unloader . Where is it located ( on firewall ? ) and where is a good source to get one. My air brake knowledge is limited. Thanks.

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Here ya go: On the firewall, passenger side: The soft line goes to unloader on compressor.
SDC10517.jpg

I originally pulled mine off and put a couple new o-rings on it. Seemed like it would be fine. Nope, a few weeks later the same issue. Just put a new one on it. Any big truck place will have one. I got mine at Cross truck parts.

IMG-20180116-202556-655.jpg

Larry

1959 B61 Liv'n Large......................

Charter member of the "MACK PACK"

 

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