When the Automotive Lift Repair Tampa Florida  system is pressurized, the check valve closes and disengages the regulator. Consequently, a leaking check valve doesn’t impact the regulator’s cutout time but does influence the cut-in time. The check valve’s role is to maintain pressure in the system during the regulator cutout, but it can’t do this if there’s leakage around the seat. Even a minor leak around the valve seat can cause the regulator to cut in faster than intended, while a significant leak leads to rapid cycling or “chatter,” as shown on the system pressure gauge. This rapid cycling is generally caused by a leaking valve, which results in a normal cutout time but a faster cut-in operation.

The regulator’s bypass valve can also leak, affecting the regulator’s cycle. If the bypass valve leaks, part of the fluid meant for the system returns to the reservoir, causing the regulator to take longer to cut out. However, once the regulator has cut out, the bypass opens and doesn’t affect the cut-in cycle.

 Maintenance

Automotive Lift Repair Tampa Florida  Hydraulic system maintenance includes servicing, pre-operational inspections, scheduled inspections, repair, and post-repair testing. Ensuring clean facilities is crucial for maintaining hydraulic system reliability, as external contaminants are responsible for more failures than internal contamination. Hydraulic contamination is discussed in detail later in this chapter. Below are procedures for maintaining common hydraulic system components.

Automotive Lift Repair Tampa Florida  Hydraulic Pumps  

All hydraulic pumps are precision-engineered. Damaged or worn pump parts typically need replacement, although some manufacturers allow minor repairs, such as restoring sealing surfaces by lapping. Light scratches, scoring, and corrosion can often be removed with a crocus cloth.

Maintenance generally involves disassembly, inspection, repair (including parts replacement), reassembly, and testing. After disassembly, clean all parts thoroughly and inspect them for damage, such as nicks, cracks, scratches, or corrosion, that could affect performance. Examine all threaded components and surfaces for wear, and check pistons, shafts, and springs for distortion. Ensure check valves seat properly, and replace any defective parts. Lubricate all internal components with the specified hydraulic fluid before reassembly.

Because pumps vary widely, refer to the relevant technical manual for detailed repair and testing instructions. Testing hydraulic pumps after repair is essential and should be done by facilities with the appropriate equipment and trained personnel. Hydraulic shops typically have the tools and expertise to test pumps and other components like relief valves, selector valves, and actuating cylinders.

Actuators  

Maintaining hydraulic cylinders is relatively straightforward, with leakage being the most common issue. Always refer to the specific technical manual for maintenance details on a particular cylinder. Maintenance for hydraulic motors is generally similar to that of hydraulic pumps.

Automotive Lift Repair Tampa Florida  Hydraulic Valves  

Hydraulic valves require minimal maintenance if the fluid remains clean, but they can occasionally fail. The most frequent issues are internal leakage and control adjustments. Valve maintenance generally involves disassembly, inspection, repair, and testing, depending on the valve type and available facilities. Some valves are non-repairable and should be replaced or scrapped when defective.

During maintenance, replace all defective, kitted, or cure-dated parts. Before reassembly, lubricate internal components with clean hydraulic fluid. After reassembly, valves should be tested for flow control, pressure settings (for relief valves and regulators), and internal leakage. Always consult the technical manual for detailed maintenance, testing, and repair procedures.

Additionally, most reservoirs are equipped with cleanout covers.

Automotive Lift Repair Tampa Florida  Accumulators  

Accumulators, which are similar in design to cylinder actuators, are repaired using the same methods. It is crucial to ensure that the pneumatic pressure is fully released before disassembling an air-operated accumulator.

Automotive Lift Repair Tampa Florida  Filters  

Filter maintenance is relatively straightforward and mainly involves cleaning the housing and replacing or cleaning the filter elements. For filters with micronic (paper) elements, the element should be replaced, while filters with porous metal elements should have their elements cleaned according to the relevant technical manuals.

Before reinstalling cleaned or repaired filters, they must undergo complete testing. This includes setting the pressure of the relief valve, checking the operation of contamination indicators, conducting leakage tests, and performing a proof pressure test. For detailed testing procedures, consult the technical manual for the equipment or filter design.

 Hydraulic System Contamination

Contamination is the direct or indirect cause of more hydraulic system failures than any other factor, making contamination prevention a top priority for anyone involved in operating, servicing, or maintaining hydraulic systems.

A single mistake, such as introducing contaminants, can lead to significant damage to equipment that can’t be easily valued. For instance, using contaminated hydraulic fluid in a line tester to service construction equipment could cause costly damage, loss of critical equipment, or even result in injury or death at the job site.

 Classes of Contamination

There are two general categories of contamination:

1. Abrasive Contaminants: These include dust, dirt, core sand, weld spatter, machining chips, and rust.

2. Non-Abrasive Contaminants: These are typically byproducts of oil oxidation or particles worn from seals and other organic materials.

The destructive action of abrasive contaminants is clear. If particle sizes exceed the clearance between moving parts, the clearance acts as a filter and traps these particles. Hydraulic pressure embeds them into softer materials, and as components move, they scratch finely finished surfaces. This leads to increased tolerances and reduced efficiency.

Oil-oxidation byproducts, known as sludge, are non-abrasive but can still disrupt hydraulic systems by clogging valves, orifices, and filters. Simply changing hydraulic fluid is not an effective solution to contamination. Abrasive particles are usually not flushed out, and friction continually generates new particles. Additionally, even tiny amounts of sludge act as catalysts, accelerating the oxidation of fresh fluid. (A catalyst is a substance that accelerates or decelerates a chemical reaction without being altered itself.)

 Origin of Contaminants

Contaminants in Automotive Lift Repair Tampa Florida  hydraulic systems can originate from the following sources:

– Particles Already in the System: These originate during the fabrication of welded components, especially in reservoirs and piping. Proper design can minimize their presence, such as using seam-welded overlapping joints rather than arc-welding open sections. Hidden passages in valve bodies that can’t be sandblasted are a primary source of core sand entering the system. Even well-designed and cleaned castings can release some sand particles under hydraulic pressure. Rubber hose assemblies also contain loose particles, many of which can be removed by flushing, though some withstand cleaning and are later freed by hydraulic pressure and heat.