Replace the piston seal in an old style Harbor Freight Lift
For many years Harbor Freight has sold these very popular motorcycle lifts. Mine is more than 20 years old and has proven to be rugged and reliable. But nothing lasts forever. A common problem with these old lifts is that the seal on the pump piston deteriorates. The symptom is leaking hydraulic fluid on the floor requiring constant topping off and eventually complete failure to raise the bed. Fixing this is amazingly easy. Before we go on I must tell you that about 3 years ago they came out with newer model that used a different hydraulic pump, not better, just different. Look closely at the pump in the picture above. If this looks like your lift then read on.
First obtain a replacement seal. Go to www.oringsandmore.com. You want a
5mm ID x 12mm OD x 6mm hydraulic U cup seal. At the time of this writing (2020) they were less than $3 each. Then raise the bed
to the top if you can and put the locking bar in place. The seal can be replaced with the bed down through the trap door but not so easily
The picture shows the pump and the linkages. The black rubber plug on the top of the pump is where you can add hydraulic fluid. If it has been leaking fluid you may have trouble raising the lift all the way because there is not enough fluid. To add fluid, lower the lift all the way down and through the trap door remove the plug. Fill the pump with hydraulic jack fluid to near the top. I got my Jack fluid from Auto Zone. Do not use brake fluid. After filling you may have to bleed the air out of the pump. To bleed it, pump the lift pedal a few times while holding down the release pedal.
Next, remove the clevis pin at the piston (the green circle in the picture). Under no circumstance should you try to remove the pin back by the spring because the spring is under very high tension. With the clevis pin removed, you can push the linkage away from the piston and that will allow the piston to slide right out. At the end of the piston you will see the bad cup seal. Mine had a big crack in it. Take the bad seal off and push the new seal on. Gently push the piston back into the pump taking care not to fold back the lip of the seal. Position the piston so you can
slide the clevis pin back in. Fill and bleed the pump as described above and you are ready to go.
Finally, you may have lost the user manual for your lift. You can download a new copy
here. It has a parts list and a replacement pump is available for $120. Replacing the pump looks like a bear of a job but I was able to fix mine in 15 minutes for just a few dollars.