TM 5-3895-382-24 Problem: Noisy vibratory mechanism. Probable Cause: 1. Low oil level in the drum. 2. Failure   of   the   vibratory   drive   shaft   or   components leading up to the vibratory drive shaft. 3. Loose retaining bolts for the vibratory motor. Problem: Hydraulic circuit oil overheats. Probable Cause: 1. Incorrect type of oil used in the hydraulic system. 2. Hydraulic oil cooler is restricted. 3. Excessive internal leakage in the closed loop circuit. 4. Low charge pressure. 5. Cooling relief valve pressure setting higher than pump charge relief valve pressure setting. 6. Failure    of    vibratory    shaft    bearings    which    causes extended periods of time over the vibratory pump high pressure reliefs. Problem: Maximum VPM is too high. Probable Cause: 1. Faulty VPM gauge. 2. Engine RPM is too high. 3. Incorrect internal displacement stops were supplied. System Tests and Adjustments Pump Efficiency Check For any pump test at a given rpm, the pump flow at 690 kPa (100 psi) will be larger than the pump flow at 6900 kPa (1000 psi).      The   difference   between   the   pump   flow   of   the   two operating 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 as a percent of pump flow is used as a measure of pump performance. Example of finding percent of flow loss: gpm flow loss Pump flow @ 100 psi X 100  = Percent of flow loss *5.5 or *57.5 X 100 = 9.5% If    the    percent    of    flow    loss    is    more    than    10%,    pump performance is not good enough. * The numbers in the examples are for illustration and are not values   for   any   specific   pump   or   pump   condition.      See Specifications for pump flow of a new pump at 690 kPa (100 psi) and 6900 kPa (1000 psi). Machine Test Install a Flow Meter.  For Formula I, measure pump flow at 690 kPa (100 psi) and at 6900 kPa (1000 psi) with the engine at high idle rpm. Formula I gpm @ 100 psi - gpm @ 1000 psi gpm @ 100 psi X 100 = Percent of flow loss Bench Test If the bench test can be run at 6900 kPa (1000 psi) and at full pump rpm, find the percent of flow loss using Formula I. If the bench test cannot be run at 6900 kPa (1000 psi) and at full pump rpm, run the pump shaft at 1000 rpm.  Measure the pump flow at 690 kPa (100 psi) and at 6900 kPa (1000 psi). 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 690 kPa (100 psi). Formula II gpm @ 100 psi - gpm @ 1000 psi gpm @ 100 psi @ 2000 rpm X 100 = Percent of flow loss 13-32