Hydraulic System Testing and Service

Question 1

List three sources of information that can be used as resources for technicians troubleshooting hydraulic systems:

Answer 1

Manufacturer service manuals
Manufacturer service bulletins
Operator manuals

Question 2

List four conditions that should be looked at when performing a visual inspection of a hydraulic system.

Answer 2

Hydraulic oil level and type
Oil leaks
Obvious damage
Machine Modifications

Question 3

It is useful to operate the machine as part of the troubleshooting process. List three things that you should be looking for while operating:

Answer 3

Machine response
Unusual noises
Engine performance

Question 4

Actuator cycle times that are longer than manufacturers specifications normally indicate:

a. excessive internal leakage
b. excessive pressure drop
c. excessive pressure
d. insufficient pressure

Answer 4

a. excessive internal leakage.

Question 5

List four safety precautions that must be observed before installing hydraulic test equipment.

Answer 5

Lower or secure all suspended loads.
Relieve the pressure from the hydraulic tank if there is a pressurized reservoir.
Relieve any static pressure trapped in the system.
Depressurize any accumulators in the system.

Question 6

If your wanted to measure the maximum pressure in a hydraulic system that is designed to operate at a maximum pressure or 18mpa, you should use a gauge with a range of:

a. 0 to 18 mpa
b. 0 to 22 mpa
c. 0 to 30 mpa
d. 0 to 36 mpa

Answer 6

d. 0 to 36 mpa

Question 7

Excessive high neutral pressure in an open center hydraulic system indicates that:

Answer 7

Excessive resistance in lines, fittings, directional control valve, filter or other return line components.

Question 8

Low charge pressure in a closed circuit hydrostatic transmission could cause __________ damage to the hydrostatic pump.

Answer 8

cavitation

Question 9

Internal leakage in a hydraulic motor can be quickly checked by measuring the amount of oil flowing from the drain line when the motor is at full load.

Answer 9

True

Question 10

When testing pump efficiency with a flowmeter, no load flow is found to be significantly lower than specification. The most likely cause is that:
A. The pump inlet is restricted.
B. The pump is overloaded.
C. The flowmeter needs calibrating.
D. Oil temperature is too low.

Answer 10

A. The pump outlet is restricted.

Question 11

In order to perform circuit leakage tests with a flowmeter, the inlet of the flowmeter is connected in series in the pump outlet line.

Answer 11

False

Question 12

What is the best source of information about how a machine had been performing prior to a failure?
A. Manufacturers service manual
B. Operator's manual
C. The operator
D. Service bulletins

Answer 12

C. The operator

Question 13

Hydraulic oil temperature is not an important factor to consider when performing hydraulic tests.

Answer 13

False

Question 14

Define the term actuator cycle time.

Answer 14

Amount of time required for the actuator to complete one cycle.

Question 15

You found that engine speed dropped excessively when performing a hydraulic stall test on an open center hydraulic system. The cause could be:
A. Increased engine power
B. Lack of engine power.
C. The system relief valve is set too low.
D. None of the above responses are correct.

Answer 15

B. lack of engine power.

Question 16

What is a snubber?

Answer 16

An orifice that is placed in the inlet of a pressure gauge to dampen pressure spike that could damage the internal mechanisms of the gauge.

Question 17

Excessively low pressures measured at the pump inlet indicates that:
A. The pump inlet is restricted.
B. The pump driveshaft speed is too high.
C. The wrong oil is being used.
D. All of the above responses are correct.

Answer 17

D. All of the above responses are correct.

Question 18

When pressure testing a hydraulic system, you found working pressure to be abnormally high. One cause for the high reading could be:
A. excessive internal leakage.
B. Slow cycle times.
C. Excessive friction or binding in the actuator or connecting linkages.
D. System relief valve is set too high.

Answer 18

C. Excessive friction or binding in the actuator or connecting linkages.

Question 19

The problem with a cylinder that heats up more rapidly than normal is:
A. It is operating at excessive pressure.
B. The return line is restricted.
C. The system relief is set too high.
D. The piston seals are leaking

Answer 19

D. The piston seals are leaking.

Question 20

Three disadvantages of testing a hydraulic system with a flow meter are:

Answer 20

1. More time consuming than performing operational tests.
2. Requires opening the system and could introduce dirt and contamination.
3. The flow meter itself may be contaminated if it was used previously on a system experiencing mechanical failure.

Question 21

Flowmeter tests showed that the no load flow of a pump is 185L/min and full load flow is 133L/min. The pump efficiency is _____%
Is the pump serviceable?

Answer 21

72%

No, the pump is less than 80% efficient.

Question 22

Why is it important to determine the root cause of a hydraulic system fault?

Answer 22

Repairing the root cause will prevent the system from failing again after the initial repair.