SFWR GP-A1004 4754781 - Caterpillar

Troubleshooting
Introduction
For Specifications with illustrations, make reference to SPECIFICATIONS FOR 637D PUSH-PULL HYDRAULIC SYSTEM, Form No. SENR7288. If the Specifications in Form SENR7288 are not the same as in the System Operation and the Testing and Adjusting, look at the printing date on the back cover of each book. Use the Specifications in the book with the latest date. For Air, Electrical and Hydraulic Systems schematics, make reference to SCHEMATICS FOR 637D TRACTOR-SCRAPER, Form No. SENR7352.The 5P5224 Pressure Gauge Kit can be used to make the pressure tests of the hydraulic system. Before any tests are made, visually inspect the complete hydraulic system for leakage of oil and for parts that have damage. For some of the tests a magnet and a measuring rule (either for inches or millimeters) are usable tools.
When testing and adjusting the hydraulic system, move the machine to a smooth horizontal location. Move away from machines that are at work and personnel. There must be only one operator. Keep all other personnel either away from the machine or where the operator can see them.
Visual Checks
A visual inspection of the hydraulic system and its components is the first step when a diagnosis of a problem is made. Stop the engine and lower all implements. When the oil is cool (so any pressure in the tank will be at a minimum), make these inspections:1. Measure the oil level. Slowly turn the filler cap until it is loose. If oil comes out the bleed hole when the filler cap is turned, let the tank pressure lower before the filler cap is removed. Look for air in the oil in the tank.2. Remove the filter elements and look for particles removed from the oil by the filter element. A magnet will separate ferrous particles from nonferrous particles (piston rings, O-ring seals, etc.)3. Check all oil lines and connections for damage or leaks.Performance Test List
Performance tests of the Push-Pull system can be used for a diagnosis of poor performance and to find the source of oil leakage inside the hydraulic system. PROBLEM: Slow bail movement. PROBABLE CAUSE:1. Relief valve setting is low.2. Valve spool in control valve does not move freely or low signal pressure from selector valve.*3. Output of Push-Pull pump is low.4. Seal failure on piston of bail cylinder. For a check of the signal pressure, see the Pump Check (Resistance) Valve story in the Cushion-Hitch Hydraulic System book, SENR7269. PROBLEM: Bail lowers too fast or does not lower smoothly. PROBABLE CAUSE:1. Loose hose connection on inlet side of pump.2. Shuttle valve does not move freely. PROBLEM: Pump makes noise and the cylinder rods do not move smoothly. There are air bubbles in the tank. PROBABLE CAUSE:1. Loose hose connection on inlet side of pump.2. Oil viscosity is not correct.3. Relief valve setting is low.4. Pump is worn. PROBLEM: Oil temperature is too high PROBABLE CAUSE:1. Oil viscosity is not correct.2. Relief valve setting is low.3. Pump is worn.4. Restriction in an oil passage. PROBLEM: Low pump output.