Hydraulic cylinder replace/repair for passenger slide

[Alan Homestead]

Hello all,  One day, while extending the passenger slide on our 2004 Monterey, the hydraulic cylinder rod (mfg = RVA) decided to fold & bend rather than to fully extend the slide. I have to admit, the coach was on uneven ground, the passenger side was tilted higher than the driver side, maybe 5 - 10 degrees (?). Apparently, there was an additional gravitational load on the rod.
Still, it was a surprise to look under the slide and see the shiny (stainless steel? chromed?) hydraulic rod in the shape of a question mark, instead of straight.
  By slowly bumping the slide retract button, we got the slide retracted so we could go home. The bent rod straightened enough to retract into the cylinder.
Now the question is, how to repair? I hope someone with hydraulic wisdom could advise me on issues like:
1. Can I replace the rod or must I replace the whole hydraulic cylinder unit?
2. Is replacing the rod a typical repair, or is that just never done?
3. If replacing the whole cylinder, should it be upgraded to a higher capacity? (thicker rod)
4. If it is upgraded, are cylinders available off the shelf (vendor?), or are they always custom made? (vendor?)
5. RVA sells a replacement cylinder for $650, but I am not sure I trust the product for capacity or quality.
6. Was the 5 - 10 degree tilt enough to cause the hydraulic cylinder failure, so that an exact RVA replacement should normally be okay?
7. Could there be another source of resistance in the slide mechanism to cause the failure? (I occasionally spray-lube the gears)
I have had to learn hydraulic theory recently, and would appreciate hearing from anyone with experience in hydraulic repair!!
Best regards,
Alan Homestead, 04 Monterey, 85,000 miles, Lake Tapps, WA

PS: I am in the middle of disassembling two RVA leveling jacks to replace the leaky seals. Am I unlucky or is RVA quality subpar?

[john brunson]

As my dad used to say, "Its the years, not the miles" ...Take them all to a local hydraulic shop, have the piston replaced in the slide cylinder, have them all honed and re"Packed"(new seals & O-rings).....  you want a pro to do this so it will last... the beauty that I see in the RVA system is the simplicity of the system~ any decent electrician/ average mechanic can repair.

[john brunson]

also, troubleshooting techniques on the RVA website.....  www.rvajacks.com

[Alan Homestead]

Interesting that you mention replacing the piston, I did not realize that is a wear-item. What goes wrong with it? Only the seals, or the piston itself?
Thanks for the advice!
Alan

[Jim Nichols]

Are there scratches on the ram (shaft) like it has been bumped or hit? Any kind of marring to the ram will compromise the seal on the end. That seal can be replaced by disconnecting the end attached to the slide. At least that's what I had to do. I polished the marring on the shaft with emery cloth. The same cloth you would use for cleaning copper pipe before soldering. I ordered the seal from HWH.

[Dave Atherton]

Alan, been around hydraulics  a little bit and would not waste money trying to strighten
The cylinder rod. At same time the piston has damaged the barrel. Yes you can attempt
To repair and rod will go in and out of barrel but packing on piston will leak oil to the out
side.you must remember hydraulic cylinder is a pressure vessel and built to very close
Spec to retain hydraulic oil under pressure. Dave Atherton Retired Cat Mechanic

[Alan Homestead]

Jim, I much appreciate the advice.

Dave, I agree, straightening the cylinder rod might not be a good idea, especially since it may be fatigued and have a tendency to bend again. If a new rod could be found (?), or made (?), maybe the repair could be completed by honing the cylinder and re-packing the piston. Finding a new rod might not be easy, but I haven't looked yet. And I don't even know if having one made by a machine shop is possible. I plan to start the repair this month (January). Thank you very much for the advice. Learning as I go!
Alan

[David T. Richelderfer]

I would think it's unusual for a hydraulic cylinder to get kinked.  Something else may be out of alignment to cause it to push crooked.

[Edward Buker]

Alan,

If you think about your cylinder damage, at the age of the components after hundreds of cycles, one would have to surmise that the original system design was sound. I say that because it had to have some hydraulic design engineering behind it given RVA was not new in this business. Many, if not all, of the large slides are hydraulic cylinder driven and I cannot remember any posts about bent drive shafts but there are seal failures and hose fails along the way. This would lead me to believe, that these hydraulic drive cylinders are adequately designed to do he job. The variable here is how difficult was it to move your particular slide in at the time it failed vs what were the drive cylinder loads when the mechanism was new and the coach was sitting level. The loads in your instance of having some slope and possibly some mechanical binding issues crossed a load threshold that could not be handled by the cylinder.

I also had a slide fail this last summer, while also parked on a bit of a tilt bringing a slide in against the coach slope (slide return uphill). My slide seemed to jump and I heard a noise that turned out to be a broken delrin roller that supported the slide. The "jump" and noise was immediate when the return button was being pressed and it could have been the slide jumping a gear tooth and coming down on the roller rather then traveling in. It could also be that the roller broke and the jumping was the dislodged roller pieces coming out.

The commonality between my fail and yours is the coach tilt, and some form of drive damage at the start of the return stroke overcoming some inertia (my case) and drive damage on the way out in your case. In both cases the slide movement load at that moment was more then the components could tolerate.

My fail lead me to look harder and do some research on products to make life easier for the slide drive rack and pinion system, rollers, and hydraulic drive cylinder. I can tell you that when I was done with the slide drive cleaning and lubrication it went in and out with a night and day difference. Most recommendations about slide lube steers you away from greasing. BCS coats the main drive rack and pinion gears and some surfaces in white grease. Rust is an issue with our older steel components and that plays a significant role in causing binding of our drives. I was reminded of riding my bike in my youth with a rusty chain and what a difference some oil made...

To have this system work freely the rust needs to be minimized on mating moving parts, the gears and rotating shafts need to be lubed, and the moving metal should be coated with something that has good lubricating qualities that does not attract dirt and is substantial enough to last. After researching options these were my choices outlined in this post and this all worked well.

http://beaveramb.org/forum/index.php/topic,5808.msg43406.html#msg43406

I also avoided, that if the coach could not be leveled, that it did not have the main slide in a down hill out/up hill in scenario or visa versa. There is inertia to overcome in the uphill direction and probably the mechanisms are at their weakest drive points when fully extended or on the way out/in. There may be some other slide alignment issues that could cause a severe load, but short of that the coach slope and slide lubrication in my opinion are likely the cause of your fail. I would not hesitate to purchase a new cylinder like the old one given it lasted 16 years. Hope you can get a better price and that this helps.

Later Ed

[Dave Atherton]

Alan, getting back to your question about rod replacement, hone cylinder barrel will in most
cases handle the internal workings. You can have a cylinder rod made and end welded on like
your cylinder rod is made. The piston packing could be a little rough and can be cleaned up
to allow seal kit to reinstall. Next thing to think about you will need to Crome cylinder rod
or in hydraulic rebuild they buy Crome rod and cut and thread for piston. Than remount
hydraulic cylinder. Yes this can be done but weighting cost my suggestion would bite the bullet and replace with correct cylinder. Dave Atherton Retired Cat Mechanic

[Alan Homestead]

Update on the RVA hydraulic cylinder on the passenger slide: I removed the cylinder and took it to 6 hydraulic shops for advice. With every successive visit, I learned more, and knew better what to ask.
   Four of them said it is a waste of effort to fix it, throw it away and buy a new one ($750 from RVA). One shop suggested to custom-make a new stronger/larger cylinder for $700. The last shop I visited was amazing. The owner immediately recognized the type of cylinder (wire-lock), and how to fix the problem. He offered to make a new rod, install new seals, and told me how dis-assemble the cylinder to save on labor. For a cash cost of $125. Holy Smoke. He suggested no need to hone the cylinder.
   I took the dis-assembled parts to him, he made a new rod, installed seals, supplied new wire for the wire-lock, and told me how to assemble the parts. He offered to answer any questions if I got stuck.
   Everything went together fine. The cylinder is self-priming so the first time the slide button was pressed the slide worked normally. Hooray! Now, 3 months later and after many slide cycles, the cylinder continues to work fine, without leak.

My amateur conclusion:
In years past, prior to its failure, I noticed that at full slide extension, the rod was slightly bent, as if the slide reached its maximum extension before the rod was fully extended. (Whereas, on the opposite side slide (driver side), at full slide extension, the hydraulic rod is perfectly straight)
   While installing the rebuilt cylinder, I noticed that the rod extended 3/8" longer than the maximum slide extension. It made sense then, that the fully extended rod had to bend slightly. A result of bad design/ bad engineering/bad slide assembly.
  So, after hundreds of slide cycles, the regular bending caused the rod to fatigue. When the MH was at the wrong angle, and more load was put on the rod, it failed by severely bending.
  I believe the long term fix is having a hydraulic cylinder with a 3/8" shorter throw. Or, have my new friend at the hydraulic shop create a new hydraulic piston for the current cylinder, 3/8" thicker -- which shortens the throw of the rod by 3/8".
 
Many thanks for the advice on this forum. Next project is rebuild 2 leaky RVA jacks - should be similar process. They've been out of commission for 10 years.
Alan Homestead 04 Beaver, Lake Tapps WA

[Roland DuBree]

Best place I have found to have RV welded jacks and cylinders rebuilt is at:   Custom Cylinders International at 1220 Enterprise Drive  Winchester, KY  40391  Grover Taylor  859-744-5544