Resealing hydraulic cylinders is an important part of equipment maintenance and most of the time can be done with a few tools and techniques. Leaking cylinders only get worse with time and can eat a hole in your pocket book and leave oil spills on your property. The majority of leaking cylinders can be fixed by a light cleaning and resealing the piston and packing head, but because it takes a decent amount of time to get the cylinder off, apart, back together, and back on the machine it is important to take a few steps to ensure that you don’t have to redo the rebuild too soon.
1. Always replace every seal
Because it only takes one seal to fail to cause a leak or weaken performance it is important to replace every seal when you are rebuilding your cylinder. Seals are wear parts and have a finite lifetime of service in a cylinder. If your cylinder is leaking from one seal failure, chances are the rest of the seals are getting close to the end of their serviceable life too. Replacing all the seals will help maximize the time between reseals.
2. Inspect the rod and barrel
Any sharp scratches, dents, or flaking chrome on the rod (shaft) or in the barrel will tear up your new seals shortly after resealing. Small scratches can sometimes be buffed out, but any large scratches or other damage should be taken to your local hydraulic repair shop to fix.
3. Clean out the seal grooves
After you’ve removed the old seals from the piston and packing head (gland) be sure to clean out any remaining seal parts, dirt, trash, or rust. Leaving this in the seal grooves will prevent the new seals from maintaining a clean sealing surface on the piston or packing head and may continue to leak after the reseal.
4. Use petroleum jelly when assembling the cylinder
Applying petroleum jelly will reduce the chances of a seal tearing or getting cut on a sharp edge of metal during assembly. Apply it to the seal grooves before installing the seals, inside the packing head (gland) before sliding it on the rod, and on the piston and packing head before sliding it in the barrel.
5. Install seals facing the right direction
Most hydraulic seals can seal in both directions, but U-cups and V-stacks are two common types that are designed to seal primarily in one direction. They have a sharp lip (either on the inside or outside diameter) that is designed to face the side that experiences the most pressure. Almost every cylinder uses a U-cup or a stack of V rings inside the packing head (gland) to seal the area where the rod comes out of the cylinder. When installing, always make sure the sharp lip is facing the bottom of the packing head so that the lip is angled down into the barrel. If the buffer seal has a lip it will always face down as well. If there is a U-cup or V-stack on the piston the lip needs to face down if the cylinder does the majority of its work extending and up if it does the majority of its work retracting.
6. Find the right seal kit for your cylinder
Getting the right seals for the cylinder you’re rebuilding makes the process go a lot smoother and ensures you have the correct type of the seal for the job your cylinder is doing. On HW Part Store we have done a lot of research to make it as easy as possible to find the right seal kits for your cylinder for a fraction of the price from the OEM and we’re adding new models of construction equipment every week.