TM   5-3805-258-24-1 H  Y  D  R  A  U  L  I  C   S  Y  S  T  E  M T E S T I N G  A N D  A D J U S T I N G Cycle  times  in  the  lift  and  tilt  circuits:  Cycle times that are longer than those shown are the result of leakage, pump wear and/or pump speed (rpm). If the basic tests give an indication of circuit leak- age, install a Flow Meter and do a system test. This procedure will find the source of the leakage. Relief valves in the tilt circuits give protection to the components from pressures in the circuits when the tilt control valve is in the HOLD position. 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, lower the bucket to the ground. To remove the tank filler cap, slowly turn the filler cap until it is loose. If oil comes out the bleed hole, let the tank pressure lower before the filler cap is  removed.  Make  the  following  inspections: 1. 2. 3. 4. 5. Measure the oil level. Look for air in the oil that is in the tank. Do this immediately after the machine is stopped. Use a clear bottle or container to get a sample of the oil. Look for air bubbles in the oil that is in the bottle. Remove the filter elements and look for particles removed from the oil by the filter elements. A magnet will separate ferrous particles from non- ferrous  particles  (piston  rings,  O-ring  seals, etc.). Inspect all oil lines and connections for damage or leaks. Inspect control linkage for bent, broken or dam- aged  components. PUMP EFFICIENCY CHECK For  any  pump  test,  the  pump  flow,  measured  in liter/rein  (U.S.  gpm)  at  690  kPa  (100  psi)  will  be larger than the pump flow at 6900 kPa (1000 psi) at the  same  rpm. The difference between the pump flow of two oper- ating pressures is the flow loss. Method of finding flow loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pump flow at 100 psi . . . . . . . . 57.5 gpm (liter/min)* Pump  flow  at  1000  psi  .  .    -  52.0  gpm  (liter/min)* Flow loss 5.5  gpm  (liter/min)* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Flow  loss  when  expressed flow is used as a measure of as  a  percent  of  pump pump   performance. Example of finding percent of flow loss . . . . . . . . . . . . . . . . . Percent gpm flow loss X 100 = of flow Pump flow @ 100 psi loss *15.5 or X 100 = 9.5% *57.5 If the percent of flow loss is more than 10%, pump performance  is  not  good  enough. *Numbers in examples are for illustration and are not  values  for  any  specific  pump  or  pump  condi- tion. See SPECIFICATIONS FOR 950B WHEEL LOADER HYDRAULIC SYSTEM, Section 2, for pump flow of a new pump at 100 psi and 1000 psi. Test On The Machine Install a Flow Meter. Run the engine at high idle. Measure the pump flow at 100 psi (690 kPa) and at 1000 psi (6900 kPa). Use these values in Formula I. Formula  I Percent gpm @ 100 psi - gpm @ 1000 psi X 100 =  of flow gpm @ 100 psi loss Test On The Bench If the test bench can be run at 1000 psi and at full pump rpm, find the percent of flow loss using For- mula I. If the test bench can not be run at 1000 psi at full pump rpm, run the pump shaft at 1000 rpm. Mea- sure the pump flow at 100 psi (690 kPa) and at 1000 psi (6900 kPa). Use these values in the top part of Formula II. For the bottom part of the formula, run the pump shaft at 2000 rpm. Measure the pump flow at 100 psi. Formula II: Percent gpm @ 100 psi - gpm @ 1000 psi X 100 = of flow Pump flow @ 100 psi @ 2000 rpm loss OPERATION CHECKS The operation checks can be used to find leakage in the system. They can also be used to find a bad valve or pump. The speed of rod movement when the cylinders move can be used to check the condition of the cylinders and the pump. 4-68