Harbor Freight Jack is Sinking
- Thread starter DesertG
- Start date
Wrench97
Well-known member
It is leaking internally past the lower piston seal.
Without tearing it down, its hard to say. My money would be on a build up of trash.
We just heavily modified 5 of those jacks for a VFX shot on the film I'm working on. I had to rework the pumps and add electric solenoid dump valves. Of the 5, there were 3 slightly different styles of pumps and parts were not interchangeable. 3 of them had O-ring seals and were filled with filthy oil and cast iron shavings, Each of the 3 styles had different sizes of ports, check balls and springs.
2 of the pumps were really nice. They had clean oil with very few shavings, small screen filters and magnets on the pump intakes and even had cup seals on the high pressure circuit. I wish I had kept track of the model numbers for the higher quality versions.
We just heavily modified 5 of those jacks for a VFX shot on the film I'm working on. I had to rework the pumps and add electric solenoid dump valves. Of the 5, there were 3 slightly different styles of pumps and parts were not interchangeable. 3 of them had O-ring seals and were filled with filthy oil and cast iron shavings, Each of the 3 styles had different sizes of ports, check balls and springs.
2 of the pumps were really nice. They had clean oil with very few shavings, small screen filters and magnets on the pump intakes and even had cup seals on the high pressure circuit. I wish I had kept track of the model numbers for the higher quality versions.
This has been my luck with every HF jack I've purchased over 25 years. After a few years they either leak, or leak down, because they use a disposable/planned obsolesce design to save a few dollars. I've given up and moved on to more expensive choices like HW and AC.
It’s hard to say, Both of those jacks utilize cartridge style valve systems that are self contained, versus your traditional Ball/seat valve system. The cartridge systems can be finicky, not only do you need them to transfer oil and Hold pressure with their internal seats, they also need to seal at both ends.
It would be rather easy to determine if it’s pump valve issue on the bottle jack, when you are done lifting the load, leave the handle in the down position and check to see if pressurized oil is back feeding into the pump cylinder as it will raise the handle. The floor jack would require some weight be added to the handle to overcome the spring return and then the same test could be ran.
At the end of the day, the jacks should be used to elevate the load and then secured with jack stands. Outside of a Valve issue on the pump side, which generally would let the load only settle a small amount before the pump cylinder filled up, it could be a Main seal is getting weak, Overload/release has some junk in the seat. Generally those last two conditions would allow the load to drop at a faster rate than overnight.
It would be rather easy to determine if it’s pump valve issue on the bottle jack, when you are done lifting the load, leave the handle in the down position and check to see if pressurized oil is back feeding into the pump cylinder as it will raise the handle. The floor jack would require some weight be added to the handle to overcome the spring return and then the same test could be ran.
At the end of the day, the jacks should be used to elevate the load and then secured with jack stands. Outside of a Valve issue on the pump side, which generally would let the load only settle a small amount before the pump cylinder filled up, it could be a Main seal is getting weak, Overload/release has some junk in the seat. Generally those last two conditions would allow the load to drop at a faster rate than overnight.
dnschmidt
Well-known member
Why would you care if it sinks OVERNIGHT. Once you've got jackstands under the car who cares if the jack sinks overnight? If you're not using jackstands Darwin will eventually remove you from the gene pool.
WWheeler
Well-known member
Jack is backup to Jack stands. Duh
After lowering the weight onto the stands, I'll raise the jack just until it touches w/o putting any weight on it just as an extra level of safety while I'm there working under it. I wouldn't leave the jack like that overnight though.
bluedog225
Well-known member
Jack oil with leak stop fixes up my misc jacks. Even dad’s old stuff. $5 on Amazon.
powertrip
Well-known member
Look here for parts.
Home | Lazzar's Floor Jack & Hydraulic Cylinder Repair Center
Lazzar's HCRC is a leading supplier of repair parts and seal kits for floor jacks, air hydraulic pumps, hand pumps and rams. We also sell Metric and Standard Seals.
www.hcrcnow.com
powertrip
Well-known member
The jack with the cup seals had to be the Super Duty model. It is the only one from Harbor Freight with those seals.