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1586 Brake Problems


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I purchased  a 1586 that didn't have working brakes.  The power steering and hyd clutch both work properly.  I went to bleed the brakes and no oil flow at the bleeder's when the brake pedals are depressed.  I took off the brake power valve took it apart and changed the o-rings. They were fine as I was hoping they were broke causing the oil to bypass so the brakes wouldn't work.

The check valve seems to operate freely when I removed it .  For some reason the oil is not bleeding off from the check valve in the power steering return line and feeding the brake system.  When I put an inline valve and pressure gauge at the power valve, I have no flow or pressure.  I know there should be around 230 psi on that circuit.

Is the MCV the next thing to check and see if there is a stuck poppet valve?  I'm kind of stumped and am not familiar with the MCV and it's workings.

I have removed the orifice in the brake power valve to make sure it wasn't plugged.

Need some 1586 mechanics help now!   

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There is a check valve block that the power steering return line is connected to and flows through.  This is where the oil is bled off to go to the brake power valve . The brake system bleeds off 1 gpm of oil from the power steering return line.

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Evidently different system than I am familiar with. Power steering on 1586's here return to mcv where it is controlled to regulated pressure. That pressure is used to operate TA, clutch booster, brakes and diff lock. Any left over goes to lube circuit. Sorry no help if different than this.

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21 hours ago, aylandacres said:

There is a check valve block that the power steering return line is connected to and flows through.  This is where the oil is bled off to go to the brake power valve . The brake system bleeds off 1 gpm of oil from the power steering return line.

Can you send a pic of this check valve block, have never seen one on a 86 series.

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18 hours ago, mrfred54 said:

Can you send a pic of this check valve block, have never seen one on a 86 series.

 

15 hours ago, snoshoe said:

My problem as well.

Best I can do is this grainy photo from the service manual that identifies connections and the parts illustration of the block.
The block in question is attached to the clutch boosted, has a plastic valve in it. 
The 1 GPM is still regulated by the orifice in the brake valve inlet.

86 Series Front of Cab Steering Connections.JPG

86 Series Brake Check Valve.JPG

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Thanks Maynard. Totally forgot that twist in circuitry. Leaves me baffled about the op's problem. Other than the check to prevent the brakes from draining back. That is just an open tee and claims pressure at the booster.

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2 hours ago, snoshoe said:

Thanks Maynard. Totally forgot that twist in circuitry. Leaves me baffled about the op's problem. Other than the check to prevent the brakes from draining back. That is just an open tee and claims pressure at the booster.

Simple block, steering return oil flows through the block, supplies clutch booster etc, oil for the brakes goes past the plastic pressure reducing valve to the brake inlet.

86 Series Hydraulic Schematic Brakes.JPG

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Again thanks Maynard. Never realized there was a pressure reducing valve in that block. Thought it was just a junction block. Don't believe that is his issue though.

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