common power steering malfunctions

Because of exposure to underhood heat, high fluid temperatures, ozone, flexing, abrasion, grease, oil and road salt, power steering hoses should be replaced at least every 5 years.

When checking power steering hoses, watch for symptoms indicating the hose has deteriorated and should be replaced:

-hose is brittle or hard
With age the hose loses its ability to expand and contract properly, and cracks appear. Exposure to excess heat (which "overcures" the rubber compounds) can cause this.

-hose is soft and spongy
A good sign that the hose has started to deteriorate inside. Oil and grease-soaked hoses are soft when squeezed, and should be replaced.

-exterior is worn
Caused by abrasion and contact with metal parts, this can eventually wear a hole in the hose, causing it to burst under pressure.
Remember that not all power steering hose failures can be spotted by exterior signs. Hoses can deteriorate from inside, causing small particles of the tube to flake off and be carried away in the fluid. These small particles can cause expensive damage to the pump, pump cylinder and other units.
Composite deteriorations are shown in the link on page 14.

Troubleshooting Guide:


Heavy Steering Effort
1. low on power steering fluid
2. loose rack piston
3. restricted fluid passages in gear assembly
4. bent or damaged rack assembly
5. internal fluid leakage in valve assy
6. external fluid leakge at pump
7. incorrect drive belt tension
8. external fluid leakage at hoses
9. incorrect engine idle speed
10. weak pump flow pressure


Hissing noise when parking
1, internal leakage in steering gear
2. steering wheel at end of travel (normal)
3. when turning steering wheel at standstill (normal)


Growl in steering pump
1. excessive pressure in hoses
2. worn cam ring in pump
3. scored thrust plates or rotor in pump
4. scored pressure plates


Swish noise in pump
-defective flow control valve


Whine in pump
1. air in power steering fluid
2. low power steering fluid level
3. pressure hose or line contacting other parts
4. mis-aligned hose and line brackets
5. missing or damaged pump cover O-ring


Rattle in steering
1. pressure hose contacting another part
2. loose pitman shaft
3. lost pitman arm
4. loose tie rod ends
5. loose rack and pinion mounts
6. loose steering gear housing bolts
7. loose steering gear adjustments

Car wanders to one side
1. incorrect front wheel allignment
2. unbalanced steering gear valve
3. loose tie rod ends


Steering wheel surges or jerks
1. low power steering fluid level
2. loose pump drive belt
3. weak pump pressure
4. sticking flow control valve


Excessive play in steering wheel
1. air in hydraulic system
2. incorrect steering gear adjustment
3. loose steering gear coupling
4. loose steering shaft universal joint
5. faulty rotary valve


Increased steering effort
1. slipping pump drive belt
2. internal pump leakage
3. low power steering fluid level
4. too low engine idle speed
5. air in hydraulic system
6. weak pump output
7. malfunctioning steering gear


Poor return of steering wheel
1. mal-adjusted steering wheel
2. dry ball joints or linkage joints
3. binding ball joints or linkage joints
4. incorrect front wheel alignment
5. mal-adjusted wheel bearings
6. kinked return hoses
7. internal pump leakage
8. contaminated power steering fluid
9. mis-aligned steering gear to steering column
10. tight steering shaft bearings or bushings
11. bent or damaged rack
12. sticking or plugged spool valve


This of course does not all fit for our BMW system, but most of it. >30 pages of education from
http://www.gates.com/ Gates Auto Education

http://www.gates.com/common/downloads/files/Gates/autoEducat ion/428-7172.pdf