Hydraulic Issues on my popup

[CaliforniaMobile]

I just bought a 1967 Alaskan cabover-style camper.  I'm having issues with the hydraulics - it's an old manual hydraulic pump and it wouldn't moved the camper. I changed out the hydraulic oil to a very lightweight airplane-fluid and it made a huge difference - the camper top raises like a charm.  Except now it takes forever to lower - it slowly, SLOWLY comes down and takes about 15 minutes when it used to take about 15 seconds! The system has four pistons and a simple hydraulic line that runs under the benches/cabinets and connects to the manual pump.  I don't think it even has a drain valve.  If anyone is familiar with these old campers I'd really appreciate your help! Could it be the bearing in the pump isn't letting the fluid back into the pump?

thanks from Oakland, CA!

[wavery]

I just bought a 1967 Alaskan cabover-style camper.  I'm having issues with the hydraulics - it's an old manual hydraulic pump and it wouldn't moved the camper. I changed out the hydraulic oil to a very lightweight airplane-fluid and it made a huge difference - the camper top raises like a charm.  Except now it takes forever to lower - it slowly, SLOWLY comes down and takes about 15 minutes when it used to take about 15 seconds! The system has four pistons and a simple hydraulic line that runs under the benches/cabinets and connects to the manual pump.  I don't think it even has a drain valve.  If anyone is familiar with these old campers I'd really appreciate your help! Could it be the bearing in the pump isn't letting the fluid back into the pump?

thanks from Oakland, CA!

There may be an adjustment on the pump. The lowering of the top takes no moving parts. It is merely the controlled release of hydraulic fluid back into the reservoir. There must be a restriction somewhere. My guess would be a flow control valve.