Author Topic: Hydraulic line replacement  (Read 9513 times)

Adam Hicklin

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Hydraulic line replacement
« on: August 22, 2013, 06:57:18 AM »
I need to replace one of the hydraulic lines on the slide out.  I plan on having one made to the correct length then install it myself.  I have zero experience with hydraulics.  This is an HWH controlled slide unit.  Uses the same hydraulic pump as the levelers.  Here are the questions:

1.  Will the line be under pressure?  There are two lines, so am I correct in assuming that one of them is always under pressure?  Either extending or retracting?
2. Once I get the line replaced, what is the process for bleeding the trapped air?
3.  What other info do I need to know, but not smart enough to ask?

I had one of the lines, which had a hole, replaced when I bought the coach.  Why I didn't think to have them both replaced is a mystery.  Not thinking I guess.  Now the second line has a couple occasional drips and some worrisome bulges.  

As always, thanks in advance.  

Joel Weiss

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Re: Hydraulic line replacement
« Reply #1 on: August 22, 2013, 05:30:33 PM »
I can't help you with the install since I didn't do it myself, but the key advice I can offer is that the lines need to be rated for >5000 psi.  The mistake made at the Beaver factory was that for some period of time they were using lines rated at ~2,500 psi or so I've been told.  One side of the line is always at pressure either with the slide fully out or in so they have to be able to withstand the pressure on a continuous basis.  Or so I've been told.

Gerald Farris

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Re: Hydraulic line replacement
« Reply #2 on: August 22, 2013, 07:47:45 PM »
Adam,
Joel is right, at least one hose is under pressure at all times in order to hold the slide in the desired location of fully extended or retracted.

The biggest mistake that is made when replacing hydraulic hoses is to let the hose rest or rub on a sharp metal edge. This will cause premature hose failure, so insulate the hose from anything that can rub on it. Another caution is to be careful when measuring the hose length, because you sometimes have to route the hose a little differently than the factory hose to gain access an clearance for installation, but you can not have the hose too long either because it is very stiff and is not too forgiving for excess length. One caution, you should almost always use a backup wrench on hydraulic fittings.

The easy way to bleed the excess air from the system is to fill the pump reservoir and run the slide in and out several times, this will purge the excess air back into the reservoir. Then top off the reservoir and check for leaks.

Gerald      

Bob Stone

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Re: Hydraulic line replacement
« Reply #3 on: August 22, 2013, 08:35:33 PM »
If I may add another cautionary note to anyone not familiar with working high pressure hydraulic hoses: never search for a leak in a hose with a bare hand. A pinhole leak, perhaps not even visible, can inject hydraulic fuel into human tissue with dire consequences.
http://www.forconstructionpros.com/article/10304708/handle-hydraulic-hose-with-care
Bob Stone
'05 Monterey Laguna IV  Cat C-9

Adam Hicklin

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Re: Hydraulic line replacement
« Reply #4 on: August 23, 2013, 06:55:12 AM »
Great advice all.  

I'll have to determine which action the leaky line is responsible for, extending or retracting.  If its retracting, that may cause a problem.  With the slide closed, I'm not sure how I would get in there to connect the new line to the hydraulic piston.  Is there a way to bleed off pressure from the line if it is in fact under pressure in the extended position?  Luckily I can see the leak.  It's about 8 iniches from the pump.  When the other line was replaced, it was obvious it was not going to be able to follow the same path as the old one through the frame rail, so we found an alternate route.  I'm sure this new one will have to follow the same route.

Any other wise words?

LarryNCarolynShirk

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Re: Hydraulic line replacement
« Reply #5 on: August 24, 2013, 04:34:03 AM »
Adam,

Measure 3 times, cut once.

Larry

Adam Hicklin

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Re: Hydraulic line replacement
« Reply #6 on: August 24, 2013, 06:37:41 AM »
I cut it 3 times and its still too short!

Adam Hicklin

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Re: Hydraulic line replacement
« Reply #7 on: August 27, 2013, 06:42:07 AM »
Follow up question and I'll try to be clear, but I don't know all the technical terms.  

The line that needs to be replaced is the one that goes to the fitting at the top, or the head of the cylinder, as opposed to the fitting at the base of the cylinder.  My best guess is that this line should make the cylinder retract thus retracting the slide.  If the cylinder is extended, this line should have no pressure.  Would that be correct, or is my logic backwards?

If I'm correct, then with the slide extended I should be able to just loosen the connections without spraying hydraulic fluid all over my new driveway.  I'm sure I'll lose some, but it shouldn't spray out, correct?

Thanks for the help!

Gerald Farris

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Re: Hydraulic line replacement
« Reply #8 on: August 27, 2013, 10:07:32 PM »
Adam,
When the slide cylinder is extended (slide out), the line that has pressure is the one that is near where the cylinder mounts to the coach frame. The line that is near to the slide end of the cylinder will be unpressurized. You can get a plastic cap from most hydraulic shops to screw onto the end of the hose when you disconnect it to minimize spills from the oil in the hose. However, you will still need a drip pan or kitty litter to deal with the oil that is unavoidably lost.

Gerald

Adam Hicklin

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Re: Hydraulic line replacement
« Reply #9 on: August 27, 2013, 11:18:42 PM »
Thanks Gerald. Wish me uck!

Adam Hicklin

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Re: Hydraulic line replacement
« Reply #10 on: January 12, 2014, 07:23:44 AM »
UPDATE:  finally got around to replacing this line.  Went very smooth.  Found an alternative route for the new hose as the original was run through the frame rail with a gazillion other hoses, tubes and wires.  I blew out the old hose and trimmed it down and will just leave it in the frame rail.  Zip tied everything tight and covered rub points with some old water hose.  Only small problem was that I needed to disconnect the hydraulic cylinder where it connects to the slide so I could get access to the hose fitting.  Not a big deal but had to do a little adjusting of the threaded eye piece that slips in to the mount on the slide.  Now when I close the slide, it pulls the slide in too much.  I know what I did and I know what I have to do to correct it.

2 questions.  Is there a way to manually operate the slide?  2.  Does the hydraulic pump (98 Marquis, HWH pump) use standard ATF fluid? Dexron II or III?

Thanks

Gerald Farris

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Re: Hydraulic line replacement
« Reply #11 on: January 13, 2014, 03:15:58 AM »
Adam,
Your slide can be retracted manually, but it is not easy. You have to loosen the hydraulic lines to the slide operating cylinder, or disconnect the cylinder, and rotate the equalizer shaft under the slide or take several men and push the slide in.

The HWH leveling and slide control system on a 98 Marquis uses Dexron III fluid.

Gerald

Adam Hicklin

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Re: Hydraulic line replacement
« Reply #12 on: January 13, 2014, 06:14:15 AM »
Thanks Gerald.  While under the slide I noticed that the end of the equalizer shaft (towards the front) had a hex end on it.  I wondered if there was some attachment that would allow it to turned.  I could probably devise something but there is not much room with the wheel well there.