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  1. #1
    Bobtail Member
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    Older Fld 120 service brake issue and air leak issue

    So Ive been a long time lurker on here. Picked up an '89 FLD last year with intentions on making it a dump truck for my bussiness, but plans have changed and now Im considering putting it on the road and doing some flatbed work with it. So onto the problems. sit for roughly 8mo. and when I fired it up the other day to move it, the "foot brake valve"...Im not sure of its exact name...seems to have stuck when I depressed the brakes. I noticed the brake lights were staying on and I have no sound of air, plus the pedal feels light to the touch, like theres no air pressure. What I want to make sure of is that the valve mounted on the firewall is the correct one. There seems to be nothing under the dash, except the rod that the pedal pivots on which depresses a smaller rod through the firewall. Is there a way for me to disconnect one or more of the lines and get the pressure to release the brakes? I know for a fact its the service brakes because the truck has a application guage and whenever the air pressure is up on the truck, the guage is showing approx 90psi.



    The other issue is an air leak behind the dash in the hvac controls. It looks like a 5 port manifold and the yellow line is leaking right at the connection. Its enough to drain the tanks within about 5 minmof shutting the truck off. Apparently Im doing something wrong because I cannot get this tiny air line to come off no matter what and its got me stumped.

  2. #2
    Bobtail Member
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    Seems as though I made a post on the air leak almost a year ago, dont remember that.

  3. #3
    Road Train Member
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    The foot valve what you need to do is remove the three bolts that hold the pedal mount on it and you will find a round piston is stuck in the bore, you need to get the piston out clean it up and lube it with some light grease and reassemble it.
    The airline under the dash it has a brass collar around the line going into the manifold, you need to push that in then the line will come out.
    Just a thought!

  4. #4
    Bobtail Member
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    Good deal. Looks like I'll be tackling both of those tomorrow. Thanks!

  5. #5
    Heavy Load Member GrapeApe's Avatar
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    When you get that airline off, squirt a little air tool oil in the lines. Those old air dash actuators were known to leak. The actuators are not expensive, but some are a real bugger to change. We use Zep Air Aid. Any time I have to go into a dash for something, I'll pull a few lines going to the actuators and give them a little shot to keep the seals soft.

    For your leak, sometimes the end of the line gets squashed a but. If that's the case, cutting 1/4" off the hose should stop the leak. If not, you may have to replace the selector valve.