301H: Hydraulic System Testing & 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’s manuals

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Question 2

What is the best source of information about how a machine had been performing prior to a failure?

Answer 2

The operator

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Question 3

What conditions should be looked at when performing a visual inspection of a hydraulic system?

Answer 3

• Hydraulic oil level and type
• Hydraulic oil condition
• Hydraulic oil leaks
• Signs of overheating
• Damaged cylinders

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Question 4

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 4

• Machine response (slow, jerky)
• Smoothness of the controls (no binding)
• Unusual noises

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Question 5

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

Answer 5

Excessive internal leakage.

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Question 6

You found that engine speed dropped excessively when performing a hydraulic stall test on an open centre 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 6

B) Lack of engine power

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Question 7

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

Answer 7

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

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Question 8

What is a hydraulic snubber?

Answer 8

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

Three Types:
- Porous Element
- Metering Pin
- Threaded Plug

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Question 9

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 9

D) All of the above responses

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Question 10

Excessively high neutral pressure in an open centre hydraulic system indicates that:

Answer 10

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

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Question 11

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 time
c) excessive friction or binding in the actuator or connecting linkages
d) system refief valve is set too high

Answer 11

c) Excessive friction or binding in the actuator or connecting linkages

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Question 12

Low charge pressure in a closed circuit hydrostatic transmission could cause what type of damage?

Answer 12

Cavitation

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Question 13

The problem with a cylinder that heats up more rapidly than normal is:

a) Operating at excessive pressure
b) Return line restricted
c) System relief valve is set too high
d) Piston seals leaking

Answer 13

D) Piston seals are leaking

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Question 14

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. (T/F)

Answer 14

True

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Question 15

Three disadvantages of testing a hydraulic system with a flowmeter are:

Answer 15

• Flowmeter testing of a hydraulic system is often more time consuming than performing operational tests.
• Connecting a flowmeter into a system requires that the system be opened up, running the risk of contamination entering the system.
• If the flowmeter was last used to test a system that has experienced a serious failure, contamination may be passed on to other systems being tested.

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Question 16

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) Pump inlet restricted
b) Pump is overloaded
c) Flowmeter needs calibrating
d) Oil temperature is too low

Answer 16

A) Pump inlet is restricted

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Question 17

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

Answer 17

False

In parellel for Tee Test

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Question 18

How is pump efficiency calculated?

Answer 18

Full load flow rate / No load flow rate

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Question 19

Flowmeters can be connected to a hydraulic system to test pump efficiency. What two connection configurations could be used?

Answer 19

Bypass: Pump oil bypasses all other system components

Inline: Pump oil through flowmeter continues through the regular system

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Question 20

What pump efficiency test connection method has the flowmeter inlet receive all the system’s oil flow and has the outlet connected directly to the reservoir?

Answer 20

Bypass Connection

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Question 21

What pump efficiency test connection method has the oil flow through the flowmeter and return back to the system to be used?

Answer 21

Inline Connection

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Question 22

How would a flowmeter be connected into a hydraulic system to measure circuit leakage?

Answer 22

Tee Test / Parallel

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