Montana Owners Club - Keystone Montana 5th Wheel Forum - View Single Post - Help! Slide-out pump drinking fluid.

ehmcfarl · 11-27-2008, 01:44 AM

These are just my thoughts IMHO.

I agree with the "closed system" theory. Don't all the slides use "double acting" hydraulic cylinders? And isn't the same cylinder that pulls a slide in used to push the slide back out? The only difference in the "pull" vs "push" action is which end of the cylinder is getting the fluid pressure applied. The "volume" of fluid in this type of "closed" system should not change. When the fluid is pumped into one end of a cylinder it is, at the same time, being pushed out the other end and back into the reservoir where it can then be sucked out by the pump to be applied under pressure to the cylinder that you are trying to move. The fluid level should never change in the reservoir. I agree that if the fluid level in the reservoir is lowering while the pump is running and applying pressure to any cylinder then this should indicate that the volume of the system is changing. The only way that the volume can change on a closed system is for a cylinder to get bigger (swell up) and I don't think that is happening, or for a hose to get longer and I don't think that is happening, or for a hose to swell up with a knot on it. I may be all wet with this theory of mine; but, a hose swelling up gets my vote. I would locate the hose that is having pressure applied to it on the long slide, try to move it in the direction that is having the problem, then stop when the problem occurs and check the entire length for a bulge. Another thought, when the fluid starts to lower in the reservoir, and before you have added any more fluid, have you tried to gently "bump" the switch just a little in the opposite direction, just until the slide starts to move, to see if the fluid level comes back up to full in the reservoir. This might prove that the hose had a bulge in it, since the valve being opened in the opposite direction would allow the fluid pressure to drop on the buldging hose and allow the return of the extra fluid back to the reservoir.

This has just been a lot of "thinking out loud" on my part. I hope it helps.

11-27-2008, 01:44 AM	#22
ehmcfarl Montana Fan Join Date: Feb 2008 Location: Signal Mtn. Posts: 280 M.O.C. #8206	These are just my thoughts IMHO. I agree with the "closed system" theory. Don't all the slides use "double acting" hydraulic cylinders? And isn't the same cylinder that pulls a slide in used to push the slide back out? The only difference in the "pull" vs "push" action is which end of the cylinder is getting the fluid pressure applied. The "volume" of fluid in this type of "closed" system should not change. When the fluid is pumped into one end of a cylinder it is, at the same time, being pushed out the other end and back into the reservoir where it can then be sucked out by the pump to be applied under pressure to the cylinder that you are trying to move. The fluid level should never change in the reservoir. I agree that if the fluid level in the reservoir is lowering while the pump is running and applying pressure to any cylinder then this should indicate that the volume of the system is changing. The only way that the volume can change on a closed system is for a cylinder to get bigger (swell up) and I don't think that is happening, or for a hose to get longer and I don't think that is happening, or for a hose to swell up with a knot on it. I may be all wet with this theory of mine; but, a hose swelling up gets my vote. I would locate the hose that is having pressure applied to it on the long slide, try to move it in the direction that is having the problem, then stop when the problem occurs and check the entire length for a bulge. Another thought, when the fluid starts to lower in the reservoir, and before you have added any more fluid, have you tried to gently "bump" the switch just a little in the opposite direction, just until the slide starts to move, to see if the fluid level comes back up to full in the reservoir. This might prove that the hose had a bulge in it, since the valve being opened in the opposite direction would allow the fluid pressure to drop on the buldging hose and allow the return of the extra fluid back to the reservoir. This has just been a lot of "thinking out loud" on my part. I hope it helps.