Need Info on Fill/Maint of Heil Dump Hoist

[Duffy]

Our 1941 1 1/2 Ton Dodge Truck has a twin cylinder Heil hydraulic hoist that has the pump and reservoir built in (see pic) and it will not go high enough.  I think it only goes to about 30 degrees.  Worse I blocked it up to work on the hoist and the block is now stuck because it will not go any higher so I can remove the block! LOL!  Hoping it just needs fluid but no idea how to add, bleed, type of oil, etc.????  I suspect oil is added thru the big brass plugs on each cylinder.  Maybe one of the lower plugs is removed and you watch to see when oil comes out??  This is a Heil model no 3S26.  Thx!!

Edited March 20, 2018 by Duffy
Fix text.

[Duffy]

OK.  After doing a little research and finding out most of the self contained units can be filled from top of cylinder, removed the brass breather plugs on top of each cylinder and dumped in 1/2 a cup of hydraulic fluid.  Made an overflow system out of clear pipe and plastic elbows and a tee and aimed stuff out of the top of cylinder connections  into a bucket.  Kept adding fluid and the hoist raised up!  Took out the block and kept adding fluid and putting clear drain hose on, then let bed down and back up.  Gained two whole inches on cylinder extension.  More tomorrow!

[Merle Coggins]

It's not uncommon to use the cylinders as the reservoir in a system like that. But there must be some extra reservoir space built in somewhere. When the cylinders extend the bottom, piston end, will hold more oil than the the top, rod end, would when retracted. So you need a little extra reservoir space to hold the the extra oil that the cylinder rod displaces. Maybe it's designed into the tops of the cylinders, or in that cross over pipe.

[Duffy]

Thanks @Merle Coggins.  Interesting thoughts.  I bet the two tops of the cylinders are connected by the crossover pipe.  I’ve been adding to each side while its up but probably only need to add to one side   It is something to think this system is 76 years old.  All I have found for info on it is advertising brochure!