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Big complicated hydraulics question

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#1 Dr.Science



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Posted 31 May 2021 - 11:44 PM

For starters, I was noodling down US 97 near Madras yesterday when suddenly the top half of the camper jumped straight up, pulled the right front hydraulic tube apart, and got stuck in an upright position. I presume this is not normal behavior, but I haven't found much documentation on why it happens or how to stop it. I opened the main hydraulics valve and lifted up the front of the camper so it was level with the fully-extended tubes in the rear (did this by lying on the front bench seat with my feet on the bulkhead and pushing up) and jostled it a good bit and finally the remaining hydraulic tubes let the top settle back into place. A slow drive back to Madras let me buy some ratchet straps to tie the top of the camper to the bottom of it, and that got me home.


First question: why did this happen and why doesn't it happen to everyone? Haven't found it documented in the manual. The previous owner told me the camper could sometimes ride up but I could avoid that by closing the hydraulic valve when traveling. Obviously not a working solution.


Then I got home and inspected the damage. The loose hydraulic tube got a bit bent. It doesn't look like a part I can replace easily, so I straightened it out by setting it on some hardwood blocks, rolling it back and forth, and tapping on the high spots with a deadblow hammer until it's pretty true. It works with motorcycle fork tubes, I figured it ought to work here. So the next question is, was that sensible as a short-term fix and where does one find a replacement tube? (This is a 1990 camper, BTW). The top tube just yanked out and appears to be a simple press fit into a brass bushing at the top, that's tapped for a bolt that attaches it to the upper bulkhead. Is this as it should be? Someone drilled a hole in the bushing and the tube, a very sloppy hole (clearly not OEM work), maybe it once held a screw to attach the bushing to the tube, screw now gone, is this necessary or even wise? (Attached photos show bushing and tube).


Given all that, it seems that now I just pop the bushing into the tube, bolt and screw it all back together, and the hydraulic system should work after a fashion. It's possible I've also bent one or more other tubes, which I'll find out when I get the top pumped up again (which is why advice on straightening them would be good). But AT BEST I'll be back to where I was before all this happened, which was:


Rear tubes seem to run more efficiently than front tubes. So when raising the top, I have to nearly close the rear-tubes valve in order for the front tubes to match the raise rate, and when lowering the top, I have to nearly close the front-tubes valve in order for the rear tubes to match the lowering rate. There is no fluid leakage except a little bit (like 2 drops per cycle) at the right rear tube, so replacing the O-rings shouldn't fix this problem. How do I fix it so all tubes raise and lower at the same rate?


Thanks in advance for your insights.

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#2 Wandering Sagebrush

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Posted 01 June 2021 - 12:38 AM

I believe there is a locking pin that goes from the top into the bottom when the top is down.  It was on the drivers side on the last Alaskan I was in.

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#3 Dr.Science



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Posted 01 June 2021 - 01:39 AM

Don't see anything that looks like a lock pin, on either side.

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#4 Jim in Idaho

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Posted 01 June 2021 - 02:26 AM

I never had this happen in all the years owned cab-over Alaskans. Or non-cabovers either. But, I never failed to close the valve after lowering.

 As far as the uneven raising/lowering, I never had that problem either, until I added a rotatable solar panel setup to one end of my current 10' non-cabover that is sitting on a single-axle trailer. That weight differential required me to install flow controllers to both front and rear cylinders. it still, isn't perfect, but better than it was. I could, probably make, it perfect, if I wanted to keep making minute adjustments to the controllers until it was right.


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#5 enelson


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Posted 04 June 2021 - 01:21 AM

The NCO models don't have the locking pin. 


The Parker flow control valves can give you some control.  https://ph.parker.co...f-series/f400s  Alaskan installs them with one valve for the front pair and one for the rear.  I still find out the overhead cabinets loading requires readjusting.


For around $1000 you can get a 4 electric actuators with a sync controller.  You'd need adapter plates or custom mounts though.  I'll switch to these once I've had enough of the hydraulics.  Also getting the space where the pump is now for storage.

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#6 wcj


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Posted 04 June 2021 - 09:14 PM

The hydraulics are fairly simple, if you can straighten the tube and it works, you are done.

On the drivers side front corner mine had a hole that allowed a pin to tie the top and bottom together when traveling. I fabricated another for the passenger side as well. A necessity dealing with cross winds. I can send pictures if wanted, but will have to be next week. 

In severe winds I frequently add a ratchet strap over the top and hooked on the jack plates. Usually only needed when cross winds are 30+, but that is not uncommon in lots of Montana. I have had it in strapped down in cross winds on Judith Gap that flipped a one ton ford and Lance in front of me. 

A manageable issue with a little thought.


Good luck

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#7 huskyrunnr


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Posted 11 June 2021 - 02:39 AM

I’ve had the top half of my 8’ nco rise up going down the road. In my case, the pirelli upholstery rubber for the seal was worn out. Others have mentioned it on here. If your seals are good and the windows were closed then I have no idea.



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