Parking Brakes ??

Discussion in 'Trucks [ Eighteen Wheelers ]' started by Waterman1000, Apr 8, 2010.

  1. Waterman1000

    Waterman1000 Light Load Member

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    Jan 18, 2009
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    Have a '69 White Freight liner. This truck (tanker) was decon from pulling tailers. No rear glades or elec and hitch. It's now a strait truck. It still has johnson bar (dose not work), even has the older emergency brake relase buttons on the dash, but don't work. But did notice when I charged one of the reserve air tanks with a compressor and press it. It blew air out an open line in back. This circute is not connect to the main brake system that I can see now. But only one knob to set brakes (Red) and I also notice it will blast a lot of air inside the dash. I notice that I can get air pressure up fast by holding down the knob. I would like to check to see why It builds to a point 30psi aprox ( just enuf to release and start crapping my pants, I alway chaulk the wheels) and won't clime unless I wait a long time or hold the knob In. I also notice that when I pull to apply the brakes the air bleeds down in around 25min to no psi with the truck shut down. This really makes me nevouse (when I have a load or not) and I would like to know what to look for to correct this. Safety Is paramount to me. Besides I don't want to look back one day and see my truck rolling, ghaaaa.... Am I being really paranoid or ???
     
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  3. Longhood379

    Longhood379 Medium Load Member

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    Nov 30, 2009
    Cremona AB
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    It sound like your truck wasn't de tractored properly
    Does it have spring brakes or just single chamber brake pots?? Something this old may not have had spring brakes. You should find a good air brake diagram for a single system and start figuring out how you truck is plumbed. Some of the older park systems required air in the system to apply (single chamber brakes) when the pressure dropped the brakes would release. The color of the knob on the valve doesn't guarentee the function, knobs can be changed. the truck park system (spring brake ) should be yellow or blue, on some 3 button systems the emergency button provided air to the trailer system with the tractor brakes applied .A little more detail on what type of system the truck has would be helpfull
     
  4. Heavyd

    Heavyd Road Train Member

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    I am pretty sure the dual air brake system didn't come out until the early 70's. I would guess this truck doesn't even have maxi brakes on it. If that were the case you would have to retrofit the whole truck to today's standards. I can't see running a truck with the old single air brake system as being legal.
     
    Last edited: Apr 9, 2010
  5. Longhood379

    Longhood379 Medium Load Member

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    Nov 30, 2009
    Cremona AB
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    The split circuit thing is a bit of a joke one side of the system only goes to the steering axle and maybe acouple of accesories, Not absolutley sure but if it meets the standards at date of manufacture it should still be road legal, but OHS won't like it on job sites with out spring brakes.
     
  6. Waterman1000

    Waterman1000 Light Load Member

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    Jan 18, 2009
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    Thanks all for the info. I'll dig out an air brake diagram in one of my manual. Dumb question, is there a way to make sure you have eather spring brakes or just air brake canisters by looking at them? She passes safety every year. As soon as the rains lets up a little I'll check out the brakes again. Oh-a little off topic. This truck is a COE sleeper. Is there a better tilt cab jack you can us to raise the cab? Changed out the older blown one for simular. But man, do I have to pump it to get the cab up. Feels like I ran several miles after :) Maybe an elect/hydro pump?
     
  7. Mjay

    Mjay Bobtail Member

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    May 18, 2009
    Alberta Canada
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    Spring brakes have 2 airlines going to each brake pot. 1 to apply service brake, and 1 to release spring brake.
     
  8. Longhood379

    Longhood379 Medium Load Member

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    Cremona AB
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    Good answer ,but.. back in the mid to late 60 s some trucks had dual piggy back style pots with the second half of the pot providing air pressure applied park brakes prolly very rare ,i have only seen 2 trucks so equiped, but something to be aware of.
    Mjay's answer is prolly correct 99.4% of the time or better, spring or often refered to as maxi brakes are applied by the spring and require air pressure to release them.

    The whole scary thing about the grandfathering policy is the assuption of knowledge about a system whose operation is 30+ years out of date,

    Some kenworth COE s ,maybe others had an air powered cab jack

    Keep that old truck running :Wrench::occasion5:
     
  9. Waterman1000

    Waterman1000 Light Load Member

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    Jan 18, 2009
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    Thansk for the input. I pulled out some diagrams. Then compaired them to the truck. Some one did some changes. The front axle have one airline going in (service brake) the back two axles have two brake canisters. Each brake canisters have 2 airlines and have "Danger Spring loaded" stamped on them. These are different than what the diagrams shows. The older one shows front axle service brake ( one airline) drive axle two canisters with one airline and the back axle have two canisters with two airlines. I want to set this truck up so the brakes are locked (parked) with or without a load. So I don't have to worry about a roll a way. I alway chaulk the wheels any way.
     
  10. Heavyd

    Heavyd Road Train Member

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    Yep, sounds like you have parking brakes for the rear. The steer axle chambers will only have one line, that is ok. Maxi or spring brake chambers are only on the drive axles. Sounds like you just have a bunch of leaks everywhere to track down now and fix.
     
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