Problem with RV power steering and brakes.

Discussion in 'Domestics' started by nickb2, Jul 15, 2017 at 10:40 AM.

  1. Mobile Dan

    Mobile Dan wrench

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    Nick said "There are two reservoirs. One for the power steering pump which can be check as any normal vehicle with a depth gauge, and another for the power brake assist assembly underneath the truck which has the actual bleeder that is used to bleed the system in neutral engine on."
    Is this correct? TWO reservoirs? POWER brake assist assembly underneath the truck? Do you mean "parking brake assembly"?
     
  2. Mobile Dan

    Mobile Dan wrench

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    Is it possible that fluid lines somewhere in the system are "reversed"?

    Looks like shift lever is moved to Park, high pressure fluid will be released from parking brake assembly and the giant spring inside will pull the giant cable to apply the parking brake. This would sent fluid back to the reservoir. The amount of fluid would vary according to how far the cable moved as the parking brake shoes went from released to applied. Worn out shoes might give you lots more fluid return to reservoir.

    If fluid amount needed to compress giant parking brake spring is a large amount, fluid level in the reservoir might drop too low as soon as shift lever is moved out of Park. Then whine, foam, foamy fluid has too much volume to fit in the system once the shift lever moves to park, because fluid in the parking brake suddenly comes back into the reservoir. Messy. Now you've got foamy fluid again.

    Possible fix...remove all unnecessary slack from parking brake cable and shoes. Get foamy fluid out of system. Set fluid level in reservoir so that it does not get too low when shift lever is moved out of Park and some of the fluid goes down into the parking brake assembly.

    The parking brake setup is kind of a brain twister, because all the switches, valves, pumps and hydraulic work together to RELEASE the parking brake. The giant spring applies it. The spring wants the parking brake to be on 24/7/365. All the rest of the system is there to compress the spring and hold it back so the vehicle will roll.
     
  3. billr

    billr wrench Staff Member

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    It seems that schematic posted (via link) is woefully inadequate. Worse yet, it may not even apply to this system since we have been advised (by dabunk?) that there are several variants of this system.
     
  4. dabunk

    dabunk wrench

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    Foaming means air in system or air entering. So if you are not leaking? How far have you or anyone actually driven it? I had one bus that I finally had to drive almost 100 miles before it purged all the air pocket. my .02 worth
     
  5. nickb2

    nickb2 Wrench. I help when I can

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    Update. Well, I seems, actually, I am pretty sure it was the HR-1 relay valve but could not test my theory.

    Sadly, the part is discontinued, so I ended up just bypassing it by way of disconnecting the shift lever to the HR-1 valve, and also disconnecting the parking brake actuator cable at the emergency brake lever beside the trans also. So he can use his emergency brake in lieu of the hydraulic park brake actuator and the HR-1 is no longer in function as the shift lever does not open the hydraulic side to the park brake actuator.

    System works flawlessly until you hook up the HR-1 valve. Has P/S and brakes all day when set up like I did with no whine, no foam/air. Also no spewing when shifting back into park. :D

    Client seemed happy with the result and says that if he goes to the states on his next vacation which is soon enough. He will try to maybe find a HR-1 valve down there. Maybe more luck there than in Montreal. But after testing out the park brake with the emergency pedal, he was happy with the bite of it and felt secure. SO he can now go on vacation which was belated due to trying to find out why this system kept gushing and and when put into gear we would loose P/S and brakes.

    We, at the shop were just happy to see this big old Class "A" leave the lot.

    Thx for all the responses.
     
    Last edited: Jul 17, 2017 at 6:57 PM
  6. nickb2

    nickb2 Wrench. I help when I can

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