TM 10-3930-641-34-1
HYDRAULIC SYSTEM TROUBLESHOOTING GUIDES
(Sheet 1 of 2)
NOTE
A failure of any component of the hydraulic system indicates the presence of other problems in the system. When troubleshooting the
hydraulic system remember that the problem you correct may be the end result of a series of malfunctions that the operator or
organizational maintenance didn't recognize - so, when you replace components, stop and think and look for causes of components
failure.
When troubleshooting the hydraulic system, examine the filter element - use a sharp knife and slice it open. When you see large metal particles you must drain,
flush and refill the system after you make necessary repairs.
When the hydraulic oil cooling system is functioning normally, the hydraulic oil will cool on the return trip of the loading cycle. If the loading cycle is short, the oil
will not get a chance to cool.
A quick and effective solution to air leaks at the hose connections is simply to add another hose clamp on the leaky connection.
Testing system for air.
If an excessive amount of air bubbles are found in the hydraulic reservoir sample bottle, do the following steps to find the source of the air leak.
1. Allow the hydraulic system to remain idle for a short period. It is characteristic of this type of system, that a short period of idleness will cause the air
bubbles to disappear.
2. Run the engine at high idle with control levers in NEUTRAL position.
3. Take a sample from the reservoir and check for the presence of air bubbles. If there are bubbles in the oil then the air leak is on the suction side of the oil
pump.
4. If there are no bubbles, maintain the engine speed at high idle and cycle the mast circuit, lift, tilt, side positioning, one at a time.
5. After each circuit, take a sample and check for bubbles.
NOTE
When pump failure is the problem, there are three areas to investigate.
1. High oil temperature
3. Aeration
Go on to Sheet 2
2-26