How do you fill a ac delco hydraulic 3 ton floor jack model 34123 with hydraulic fluid

=release the valve so no pressure in cylinder.
-clean area around filler hole on both cylinders
-use compressor to blow out area so no contaminants in hydraulic cylinder.
-USE ONLY HYDRAULIC JACK FLUID
-fill cylinders till you can see fluid just below opening
-close valve to activate jack
-bleed cylinders by pumping arm of jack to remove air from cylinders 10-15x.
-replace filler hole plug
-test jack (if doesn't work properly, bleed again

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possible blown internal seal

Presume it a hydraulic jack. Most are sealed, some of the more expensive types will have a valve, usually hidden somewhere.
But what you need to look for first is where it is leaking from.
If it has lost fluid chances are one of the seals have blown.

Sounds like a bad seal on that plunger that pumps up and down. That plunger should unscrew and then it's pilled out , there should be an O ring. That is where it probably is leaking. You probably need to top off oil. You can jack oil in an auto store or Lowes, etc.

MOST JACKS HAVE A BOLT LOOK PLUG TO REFILL THE JACK AND YOU DO IT WITH THE JACK AT THE LOWERS POINT, SOME HAVE A RUBBER PLUG. YOU CAN USE P/S FLUID OR TRANMISSION FLUID TOO TO REFILL IT.

Dan, just a guess but my floor jack has two set type screws in the top of the base. Take out one of the screws and turn it over to drain out the fluid into a pan or use a suction tool to remove it. Then fill it up again. good luck

It was made by Hein-Werner, Similar to the WS model also 3,000lbs (not 3 tons). Been out of production at least 20 years or more. Guardian was Hein-Werner's cheaper off brand. Kind of a "dumbed-down" version. Also made an H-101 which was similar to H-W OS (O-Boy) model of 2500lbs.

Try a hydraulics dealer who sells Hein Werner parts. although obsolete, about 1/2 the parts are still available.

Lastly: Hydraulic jack oil. Never use brake fluid. Engine oil in a pinch, by I would never do it.

Sounds like it needs some hydraulic fluid added.Look for a rubber plug or screw on the side of the hydroelectric cylinder where the ram comes out.Buy a zoom spout oilier and save the oil.Use some solvent and clean it out.Add some hydraulic fluid and fill until it starts to come out.You may be able to find an oil can that will work for you. Leave the jack in the closed position when you fill it.

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how do i bleed my floor jack

Hi,

I think I have the same jack. Th serial number was on a little sticker that is long gone,but the model number you need might needs is: 875.501390.

Hope this helps.
Gary