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Hydraulic Pump and Hoses


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A moth or so ago I posted that I had a broken hydraulic hose right at the pump. Cummins turned me down as they said they couldn’t figure out the routing but they just didn’t want to take on a dirty job!

 I took my coach back to the REV service center in Decatur and they put on a new hose and filled it with Dexron IV fluid and said it was good. We left to go home and got to the campground and the new hose blew out of the fitting and emptied the reservoir!  We are now back in Decatur for repairs. 
My question is why would that hose fail?  Can the pump over pressurize the system?  We had not even tried to level the coach. I stopped at a rest area about an hour before and there were no leaks then. Does the pressure in the pump vary or is it constant?  This system only serves the levelers and not the radiator fan or power steering  

 I’d like to hear your comments so I have a better knowledge of this system. 
 

Tom Gibbens

15 Dynasty 

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hoses break from flexing.  Ensure the hoses are tie wrapped to keep them from bouncing around.

The pump only runs when using the leveling system.  On mine, one is not supposed to run the system more than 5 minutes at a time with like 15 minutes cooling period inbetween.

I love these Cummins replies...prima donnas that charge an arm and a leg.

Pressure wash and degrease the underbody so the princesses don't mind the next time...

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Do you know for sure why the first hose failed??? Did the hose fail, did the fitting fail, was the fitting loose.

The hydraulic jack and pump application in an RV is extremely light duty.  The hoses are designed and tested for thousands of cycles.  There is really no movement in the hoses as the pump and jack are stationary and the hoses are routed along a ridged frame.  On my system there is a relief valve in the valve block that can be adjusted to increase pressure and the ability to lift more weight.  My system seemed a little weak so I did increase the pressure a little but it is still withing the capability of the hydraulic hose pressures. 

When you have this fixed I'd request to see the hydraulic hose and fitting.  It is possible the hose was not crimped properly. 

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I have a 2003 Beaver with hydraulics for the two slideouts and the jacks. I had a hose leaking at a fitting near the manifold for the pump. I thought I could cut the hose back and put a reusable fitting on it. The hose is rubber and we could not get a reusable fitting to stay on. Was told the reusable field replaceable fittings will not work on rubber hoses. Finally just replaced both hoses going to that slideout with all new fabric like covered hoses. 

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  • 3 weeks later...
On 10/31/2022 at 2:49 AM, jacwjames said:

Do you know for sure why the first hose failed??? Did the hose fail, did the fitting fail, was the fitting loose.

The hydraulic jack and pump application in an RV is extremely light duty.  The hoses are designed and tested for thousands of cycles.  There is really no movement in the hoses as the pump and jack are stationary and the hoses are routed along a ridged frame.  On my system there is a relief valve in the valve block that can be adjusted to increase pressure and the ability to lift more weight.  My system seemed a little weak so I did increase the pressure a little but it is still withing the capability of the hydraulic hose pressures. 

When you have this fixed I'd request to see the hydraulic hose and fitting.  It is possible the hose was not crimped properly. 

Hi!  Can you give me an idea of how to do this??  Our pump no longer lifts the front end.  Tried another pump, same issue..

Thanks!!

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OK, but warning that anyone that does this there is a risk. 

When I was having trouble I did a bunch of research & searches and ultimately found the attached document that details how to do this.  Basically on the side of the valve block that you can adjust to raise or lower the pressure.  I use to work on a lot of different types of diesel hydraulic equipment and am very familiar with how these systems work.  The relief valve has a heavy spring that restricts pressure as you tighten the adjusting nut.  The restriction in turn result in higher pressure within the circuit.  

Ideally you'd want a pressure gauge to do this but I just increased the pressure relief valve by a quarter turn and tested and quit when I was satisfied.

The pump system is the same on a  lot of rigs, whether Monaco adjusted correctly from one model to another based on weight is IMHO doubtful.  Most of the cylinders are the same size/design and capable of higher pressures.  Hoses are probably the same pressure rating.  SO I was comfortable doing this. 

Now when I lift the coach it doesn't stall out, it keeps raising until  the cylinder bottoms out.  Same with the rear jacks.  Last year I wanted to check the front wheel hubs for any play, put a block under the front jack and easily raised the rig high enough to do this.  AND my rig is pretty darn heavy!!!!

But proceed at your own peril

_RVA Jacks - How To Increase Pressure.pdf

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We went to the service center in Decatur, IN and they thought they had it fixed but it failed a second time. The first time it was a broken hose right at the fitting and we lost all fluid in the pump. I disconnected the pump once we got to our site. The second hose blew the hose out of the fitting at the pump and we lost fluid again. They replaced that hose but the pump failed and couldn’t not be bypassed so they replaced the pump and all is well now. 
 

Cummins said the ruptured hose was a front leveler hose but the Decatur Tech said it was a rear leveler hose and they replaced it! But that hose blew out of the fitting and then they said it was a front leveler hose when in fact it was the hose they replaced. We were not billed for the second hose and I suspect they screwed up!  At least it is fixed now. 

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The system that the hydraulic shops use to make these hoses require that the correct die be used to crimp the fitting based on the hose size.  The hydraulic crimper then has a setting to adjust the length of stroke on the hydraulic ram.  Not saying you can't make a mistake but it is possible.  If it is done right the hydraulic hose would fail before it blows off the fitting.  

At least they fixed the problem and you didn't have to pay for their mistake. 

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