259D Skid Steer Loaders Machine Systems – Hydraulic Oil Contamination – Test

------ WARNING! ------

Sudden movement of the machine or release of oil under pressure can cause serious injury to persons on or near the machine.

To prevent possible injury, perform the procedure that follows before testing and adjusting the hydraulic system.


------ WARNING! ------

Escaping fluid under pressure, even a pinhole size leak, can penetrate body tissue, causing serious injury, and possible death. If fluid is injected into your skin, it must be treated immediately by a doctor familiar with this type of injury.

Always use a board or cardboard when checking for a leak.



Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting, and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids.

Refer to Special Publication, NENG2500, "Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Cat products.

Dispose of all fluids according to local regulations and mandates.


If the hydraulic oil becomes contaminated, premature component failure could result. Contaminated hydraulic oil can also contribute to overheating. Use the following procedure to sample the oil in the hydraulic system.

The recommended level of cleanliness for the hydraulic system is ISO Code 18/15. Refer to 1 for the maximum allowable particle count.

Note: The concentration of the particles by size should be monitored over a series of samples. This information can be used in order to spot abnormal wear before a failure occurs. A spectrographic analysis of the samples can be used in order to identify the composition of the particles. The analysis of the oil sample may be used in order to identify the components that are failing.

Table 1
Hydraulic Oil Contamination    
ISO Code     Particle Size (Microns)     Maximum Number of Particles Per 50 mL Sample    
18     6     125000    
15     14     16000    


The standard hydraulic oil in this system is SAE 10. If the hydraulic oil becomes contaminated, premature component failure could result. Contaminated hydraulic oil can also contribute to overheating.

Required Tools

Table 2
Parts List    
Quantity     Part Number     Part Description    
1     162-5791     Shop Towel    
2     169-8373     Sample Bottle Group    
1     162-8873     Sample Bottle Probe Holder    
1     8T-9208     Probe Assembly (1)    
( 1 ) Purging with tube

Test Preparation

  1. Start the engine and run the engine at high idle.

  1. Operate all of the hydraulic cylinders through a minimum of ten full cycles. This operation will allow the oil temperature to reach the normal operating temperature.

  1. Lower the bucket and any attachments to the ground.

  1. Install a jumper line between the auxiliary lines on the lift arms, and cycle the auxiliary flow for 1 minute.

  1. Open the engine access door.

  1. Set the throttle position to low idle.

    Note: Do not operate the hydraulic controls.

    Note: Remove any dirt or debris on the sampling valve that is located at the hydraulic oil filter base.

Test Procedure

ReferenceFor more information refer to Special Instruction, SEBF8482, "Obtaining Oil Sample for Analysis".

Illustration 1g03410744

Oil Sampling Port

(1) SOS port

    Illustration 2g03383212

    Sample bottle package

  1. Open the 169-8373 Sample Bottle package. Remove the sampling probe tube from the bag.

    Illustration 3g03383214

    Probe holder and probe

  1. Insert the open sampling probe tube into and through the 162-8873 Sample Bottle Probe Holder counter bored end. Pull the probe tube all the way through the holder until the sampling needle seats in the holder.

    Illustration 4g03383218

  1. Remove the sampling bottle from the package. Install the cap with two holes onto the bottle. Install the probe tube into one of the holes in the cap.

    Illustration 5g03383221

  1. Return the assembled bottle and return the probe back into the package in order to prevent contamination.

  1. Remove the dust cover from the S·O·S valve (1) .

  1. Clean the S·O·S valve with a clean 162-5791 Lint Free Shop Towel .

  1. Purge the S·O·S valve by pressing the 8T-9208 Purge Probe onto the S·O·S valve. Purge a minimum of one sample bottle of oil or more. More than one sample may be required to ensure all the dead volume of the fluid is purged and the sampling nipple is internally cleaned.

  1. Properly dispose of the purged oil.

  1. Remove the prepared sample bottle from the package.

  1. Rinse the sample bottle and rinse the probe tube with the system oil. Rinse the bottle by filling the bottle half full with the system oil.

  1. Shake the sample bottle vigorously for several seconds.

  1. Then empty the oil into a waste oil container.

  1. Fill the sample bottle to the "fill range" imprinted on the bottle, but do not fill beyond the fill mark.

    Note: Do not fill the bottle beyond the fill mark. Filling beyond the fill mark will not allow for proper lab mixing.

  1. Remove the sampling probe tube from the bottle lid. Save the knurled probe holder and discard the probe tube.

  1. Immediately replace the two-hole lid on the sample bottle with the solid lid (no hole). Dispose of the lid with two holes.

  1. Wipe any oil off the sample valve.

  1. Install the dust cap onto the S·O·S valve (1) and check that the cap is clean on the inside.

  1. If the concentration of contaminants is higher than the values in Table 1, flush the hydraulic system. Refer to Testing and Adjusting, "Hydraulic System - Flush and Fill" for the correct procedure.

  1. If the concentration of contaminants continues to be higher than the values in Table 1, change the hydraulic oil. Refer to Operation and Maintenance Manual, "Engine and Oil Filter - Change" for the correct procedure.

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