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Unit Operating Information

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All Geoprobe® machines use Mobilfluid 424™ Hydraulic Fluid. If Mobilfluid 424™ is not available, alternative fluid brands include Phillips 66 Philube™ HG Fluid, and Cat® HYDO™ (Hydraulic Oil).

Part numbers for Cat® HYDO™ are:

  • 1 gal container = 8T9579
  • 5 gal pail = 8T9580
  • 55 gal drum = 8T9581

Hydraulic Oil ReservoirThis gauge shows the hydraulic oil temperature.

Operating temperature range for Mobilfluid 424™ is
-40 degrees F ~ 180 degrees F (-40 degrees C ~ 82 degrees C).

  • Extremely hot fluid temperatures mean it is more likely to cavitate. Over-heated fluid thickens (viscosity increases) because additives are cooled out. High operating temperatures for sustained periods will cause the fluid to break down.

If fluid becomes too hot, it is recommended to operate probe cylinder (with no load) to help circulate fluid through the cooler. This only applies to Geoprobe® 66 and 77 series direct push machines.

  • This process allows large volumes of fluid to flow through the cooler under low pressures (usually less than 1000 psi) thereby rejecting its heat through the cooler element.

Change hydraulic fluid and filter after the first 200 hours of operation, and then every 500 hours of operation or 12 months, whichever come first.

Hydraulic Fluid Capacities: Refer to your Geoprobe® Owner’s Manual for system capacities.

  • When it’s time to replace the hydraulic fluid, fill to the full-line either on the dipstick or as noted by the decal near the sight glass on the hydraulic reservoir. If there is no decal near the sight glass, then fill to about one inch below the top solid black line on the sight glass. The hydraulic fluid level is checked with all cylinders retracted (in) and when hydraulic fluid is cool or before any work has been performed by the unit.


Engine Compartment


Use SAE 10/15W-30/40 for all weather conditions

Do not over-fill oil pan.

  • This can cause engine oil to be drawn into the combustion chamber and burned along with the fuel.
  • Over-revving or over-running of the engine can occur because the engine oil is being burned along with the diesel fuel.

Change engine oil after the first 50 hours of operation, and then every 200 hours of operation or every 12 months, whichever comes first. Refer to Kubota operator’s manual for procedures…

Engine Oil Capacities:

  • 7730DT: 14 quarts (check level after 13 quarts)
  • 6620DT, 6610DT, 66DT, and BP49: approximately 9 quarts (check level after 8 quarts)
  • 540UD and 54LT approximately 6 quarts (check level after 5 quarts)
  • 54DT: approximately 7 quarts (check level after 6 quarts)




(as recommended for all Geoprobe® direct push machines powered by a Kubota diesel engine)

Operating angle should not exceed 20 degrees in any direction for continuous operation.

No more than 30 degrees any direction for intermittent operation (less than 10 minutes).

  • If operating angles of the engine exceed 30 degrees, the engine could starve of oil.


Air Filter

Geoprobe Systems® uses a 12 volt 535 CCA top post battery to power our units. (CCA stands for Cold Cranking Amps.) You can go with a higher rated CCA battery if you would like. Be sure to take a measurement of the height, width, and length of the existing battery in your unit. It is important that the new battery is the correct-sized battery dimensionally in order for it to fit in the location it was designed to go in as well as work with the battery tie downs provided for it.