06/12/2000
Hydraulic floor jacks are indispensable tools in any home or professional garage, simplifying the process of lifting vehicles for maintenance and repairs. However, like all mechanical devices, they are subject to wear and tear. A common issue that leads to a floor jack losing its lifting power is a worn or damaged ram seal. This article will guide you through the intricate process of rebuilding a hydraulic floor jack, with a specific focus on identifying and replacing the ram seal, ensuring your jack can once again perform its vital function.
Understanding Hydraulic Jack Failure
A hydraulic jack operates on the principle of Pascal's Law, using an incompressible fluid to multiply force. When your jack fails to lift, or leaks down, it often indicates an internal issue. While low fluid levels or air in the system can cause problems, persistent issues, especially after attempts to purge air and top up fluid, strongly suggest internal leakage. This is frequently due to degraded seals, particularly the ram seal, which is critical for maintaining hydraulic pressure.
The lifespan of a hydraulic jack can be considerable, with older, well-made models often lasting for decades. However, after forty years of service, as in the case of the jack discussed, internal components, including seals, are bound to degrade. Attempting a rebuild can be a rewarding experience, saving you the cost of a new jack and extending the life of a reliable tool. Be prepared, however, as this is not a simple task and may require the fabrication of special tools.
Essential Preparations and Parts
Before embarking on this project, it's crucial to obtain the correct rebuild kit. Generic 'O' rings from a hardware store are unlikely to suffice; you'll need a kit specifically designed for your jack model. Identifying the correct kit can be challenging, especially for older or less common brands. Contacting manufacturers or suppliers with your jack's brand name and model number is highly recommended. The author found that their 'Fleet' branded jack was actually manufactured by someone else, requiring a kit for a Lincoln/Walker jack.
A typical rebuild kit contains numerous parts, often exceeding 19 items, including various 'O' rings, neoprene seals, steel balls, and copper washers. It's advisable to keep the kit unopened until you've disassembled the jack to ensure the parts match your specific components. This will prevent difficulties with exchanges if the wrong kit was supplied.
Choosing the Right Fluid
Crucially, always use hydraulic jack fluid. Never substitute motor oil or brake fluid. Brake fluid, in particular, will cause the seals to swell, exacerbating the problem. Hydraulic jack fluid is specifically formulated to maintain its viscosity across a range of temperatures and is compatible with the rubber and metal components within the jack.
Disassembly: Getting to the Ram Seal
The process of disassembling a hydraulic floor jack involves carefully separating its constituent parts. A floor jack is essentially a bottle jack mounted horizontally within a frame. The initial steps involve:
- Spreading the Jack Frame: Loosen the nuts on the lift arm axle to allow the frame members to be spread apart. This provides access to the bottle jack unit.
- Removing Bolts: Locate and remove the bolts securing the bottle jack unit to the frame. There are typically two bolts on each side.
- Separating the Handle Mechanism: Carefully spread the frame further to detach the handle and its associated yoke casting. This may require some gentle persuasion.
- Detaching the Bottle Jack Unit: Once the frame is spread sufficiently, the bottle jack unit can be lifted out, though it will likely still be attached to the lift arm by hinged extensions. Remove any retaining pins or springs holding these components together.
Opening the Bottle Jack Unit
This is where specialized tools and considerable force may be required:
- Draining the Oil: Place the bottle jack unit in a suitable pan and drain as much of the old hydraulic fluid as possible.
- Removing the Ram Nut: The ram nut, or tank nut, which secures the ram to the bottle jack unit, is often extremely tight. It may require a specialized spanner wrench or, as in the author's case, a custom-fabricated tool. A sturdy vise and significant leverage are essential. Be prepared for the possibility of needing to weld or modify tools for this step.
- Further Disassembly: Once the ram nut is removed, the ram can be pulled out. The outer shell of the oil tank may appear fixed but can usually be tipped off. Remove the wire mesh oil filter and set it aside. Unscrew the release valve assembly and carefully remove the cone-shaped plug. The plunger mechanism can then be unscrewed from the base, often requiring a firm tap with a hammer on a wrench to break it free.
Addressing Internal Valves and Seals
The bottle jack unit contains several critical valves and seals:
- Check Valves and Safety Overload Valve: These are typically accessed via threaded plugs in the body of the unit. Removing these plugs can be challenging, and the screws are often very tight. The author had to fabricate a specialized screwdriver from a hardened bolt to remove the screw for the check valves. The safety overload valve's setting is crucial; it regulates the maximum pressure the jack can generate. It's important to note the original setting (e.g., 1 3/4 turns out from bottomed) for reassembly. Be extremely careful when working with these components, as the small balls within the valves can be easily lost. Using a shallow pan or box to contain any dropped parts is highly recommended.
- The Plunger Seal: The plunger has a single seal at its end, often made of a smooth machined surface or a specific type of seal without an 'O' ring or washer. Replacing this seal requires compressing a strong spring within the plunger. A special tool, often made from wire and used with a drill press, can aid in collapsing the spring to allow the retaining 'C' ring to be removed and replaced.
Replacing the Ram Seal
This is the core of the rebuild process for a jack that won't lift:
- Accessing the Ram Seal: The ram seal is located at the bottom end of the ram, within a groove. It can be difficult to remove due to its hardened state after years of service. A small screwdriver or similar tool may be needed to pry it out. Be careful not to scratch the ram itself. Remove any nylon collar behind the seal and clean away debris.
- Selecting the Correct Seal: Rebuild kits often contain multiple ram seals. It's vital to select the one that precisely matches the cylinder's opening. Measure the cylinder bore with a caliper and compare it to the dimensions of the seals in the kit. A seal that is even slightly too large will make installation extremely difficult.
- Installation: The new ram seals are typically made of a tough material and may not be very pliable. You might need to press down on the ram while positioning it over the seal's opening to get it started. Then, carefully work the seal onto the ram. The open, cup-like portion of the seal must face the bottom of the ram and the jack unit.
- Cleaning and Lubrication: Ensure the ram and the inside of the cylinder are thoroughly cleaned of any grit or debris. Coat both the new seal and the inside of the cylinder with fresh hydraulic jack fluid before inserting the ram.
Reassembly and Filling
With the new ram seal installed and other components addressed, reassembly is the reverse of disassembly:
- Reassemble the Plunger: Carefully reassemble the plunger, ensuring all parts, especially the small balls for the valves, are correctly seated. Tighten the locking nut on the plunger assembly until the plunger operates smoothly but without sluggishness.
- Reassemble Valves: Reinstall the check valve screws and the safety overload valve, ensuring the correct settings are maintained. Use new copper washers where applicable.
- Reattach Tank Shell and Ram Nut: Clean the tank shell and the ram nut thoroughly. Replace the neoprene seal ring in the ram nut. Apply jack fluid to mating surfaces and thread the ram nut back onto the bottle jack unit, tightening it securely.
- Mount Bottle Jack Unit: Bolt the bottle jack unit back into the jack frame, ensuring the handle mechanism is correctly positioned.
- Fill with Fluid: Use a funnel with a narrow tip to fill the reservoir with fresh hydraulic jack fluid. The amount of fluid needed can vary, but it's often around 12 ounces for a typical floor jack, with the remainder used for flushing.
- Purge Air: With the release valve open, periodically pump the handle to draw fluid through the system and expel any trapped air. Repeat this process several times until the ram lifts smoothly. Fully extending and slowly lowering the ram multiple times can help remove stubborn air pockets.
Final Checks and Maintenance
After refilling and purging, check the fluid level. It's normal for a jack to expel a small amount of excess oil through the reservoir cap's filter, especially during initial use as trapped air is released. Monitor the oil level and top up if necessary. Regular maintenance, including periodic fluid changes and inspection of seals, will prolong the life of your rebuilt jack.
Frequently Asked Questions
Q1: Can I use any type of oil in my hydraulic jack?
A1: No, it is critical to use only hydraulic jack fluid. Other oils, like motor oil or brake fluid, can damage the seals and internal components.
Q2: My jack still doesn't lift after replacing the seals. What else could be wrong?
A2: Other potential causes include blockages in the hydraulic lines, worn pump components, or issues with the check valves. A thorough cleaning of all internal passages and components during the rebuild is essential.
Q3: Is it always worth rebuilding an old hydraulic jack?
A3: For older, well-constructed jacks (often those made in the USA), rebuilding is usually cost-effective and extends the life of a reliable tool. For cheaper, low-quality imported jacks, the cost of parts and labour might approach that of a new, comparable jack, and the quality of the original components may not justify the effort.
Q4: How often should I change the hydraulic fluid?
A4: While some manufacturers recommend changing the fluid annually, a good rule of thumb is to change it if it appears dirty, contaminated, or if you're experiencing performance issues. Flushing the system during a rebuild is also a good opportunity to start fresh.
Q5: I can't find a rebuild kit for my jack. What should I do?
A5: Try contacting the manufacturer or a specialized hydraulic parts supplier. Providing the exact model number and brand is key. If a specific kit isn't available, you might consider taking the bottle jack unit to a professional hydraulic repair shop.
If you want to read more articles similar to Revitalising Your Hydraulic Floor Jack: A Comprehensive Guide, you can visit the Automotive category.