As a car user you are apt to know all about oil change although this generally applies to changing engine oil. A vehicle contains other liquids as well and their change should not be neglected. In addition to gearbox oil and the oil in the differential, power steering oil does not last forever. We will show how to change the oil for the brake and power steering.
Components and function of power steering
The power-assisted steering is a module which makes the steering wheel turn significantly lighter. Initially this was exclusively developed for trucks, but is now standard in compact cars as well. Power-assisted steering comprises
– a hydraulic cylinder
– a hydraulic Pump
– hoses
– an expansion tank
Generally, the hydraulic pump is driven by a belt. The revolving movement builds up pressure, enabling the power-steering system. The hydraulic cylinder is mounted directly on the steering rack. As soon as the steering wheel is turned in a certain direction, the cylinder supports the steering motion in that direction.
The pressure is sufficient to make the steering lighter, though not enough to cause independent movement. The transmission of pressure is enabled with help of power steering fluid. As long as it is fresh and pure, it works fine.
When power steering oil is up for replacement
Fresh power steering oil has a raspberry colour. Old oil turns murky brown due to abrasion, effects caused by the engine heat or particle intrusion. Yet, virtually no car manufacturer prescribes a fixed interval for power steering fluid change. As a rule of thumb 80,000 – 100,000 km can be maintained. When reaching this mileage, the power steering oil is at least up for a check.
Too old power steering oil causes noises increasingly becoming louder. The steering wheel can develop slight play or alternatively become heavier to handle.
Fresh power steering oil spares all power steering components and extends their life span.
Power steering oil change is not specifically prescribed or essential and therefore no standard components or procedures have been developed by car manufacturers. In contrast to the easily accessible oil drain plug and oil filter for the engine oil change, power steering oil replacement is slightly more complicated.
A good moment is the timing belt replacement. Its maintenance intervals have become much longer. More than 100,000 km is now standard for these wear parts in normal cars. Replacing the timing belt can be combined with the inspection or replacement of the power steering oil. The operation of the power steering pump can be checked as well. As long as it is running smoothly and silently, it is still in good condition.
Step-by-step replacement of power steering oil
For power steering oil change the following tools and equipment are required:
– car hoist
– wheel wedge
– axle stand
– vacuum pump
– bowl
– new expansion tank
– fresh and suitable power steering oil
– an assistant
| Important: When changing oil, the power steering pump should never be allowed to run dry to prevent it from sustaining damage. |
1. Jacking the car up
The car must be jacked up in such a way that the front wheels can turn freely. This is very important for venting the power steering system. First, the car is lifted with a car hoist and then positioned on suitable axle stands.
| Important: only use professional car axle stands. All other solutions such as wood or stone blocks, or a simple hydraulic jack are very dangerous. |
The car should always rest on the provided supports. An incorrectly positioned jack stand can warp the bodywork.
After lifting the vehicle front, the rear wheels are secured with wedges.
2. Removing old power steering oil
To access the expansion tank, removing certain components might be necessary. In any case, the bowl should be placed in the proximity of the expansion tank avoiding an unnecessary long flow and pollution of the engine compartment. Suitable bowls are wiper tanks cut in half or old kitchen bowls.
The power steering oil is directly sucked from the expansion tank with a vacuum pump and transferred to the bowl. A suitable pump costs about 25 EUR (± £22) and must be suitable for oil and petrol.
3. Removing residues
The vacuum pump does not remove all power steering oil. Therefore, a bit of fresh oil must be “sacrificed” to rid the system completely of old oil. Now, the assistance of a second person is required.
First remove the expansion tank to enable you to access the hoses. The supply hose is pulled from the expansion tank and put in the bowl. The hose can be identified by its larger diameter.
Then plug the inlet with tape or other material.
Now pour some fresh hydraulic oil into the tank. Your helper should start the engine and turn the steering wheel alternately fully to the left and right. Fresh hydraulic oil must be added constantly to keep up with the power steering pump to prevent it from running dry. Once the raspberry-coloured, fresh oil starts running into the bowl, the engine should be switched off.
Now, the hydraulic power steering system is flushed or “bled”.
4. Replacing the expansion tank
The expansion tank’s integrated filter cannot be removed. Maintenance of a hydraulic power steering system always includes replacement of the expansion tank.
| TIP: Cut the supply and drain hose of the expansion tank at their mounting supports and use new hose clamps. |
Hoses tend to lose tension in the depressed areas and start leaking. Connect the new expansion tank with shortened hoses. The hoses and mounting supports have individual diameters, excluding the risk of unintentional swapping. Depending on car model, a new expansion tank costs 5 – 15 euro; these additional expenses for oil replacement are not excessive.
If hoses are porous, they must be replaced as well. Porous or cracked hoses tend to leak, which can lead to dangerous driving conditions.
| TIP: check the hoses on tooth marks of rodents such as pine martens or weasels. These can be identified by opposing bite marks. If a rodent has nestled in the engine, immediate action is required: a major engine cleaning and an ultra-sound installation are durably effective. |
5. Adding power steering oil
Finally, the fresh power steering oil is added. The assistant starts the engine again and during the refill turns the steering wheel to the left and right repeatedly, thus venting the hydraulic system. As soon as the oil remains in the expansion tank, stop adding. Now the unscrewed lid is put on the expansion tank and lifted up again. The oil level is shown on the integrated oil dipstick. It should indicate the most “full” state. The hydraulic system should however not be too full. If the highest mark is exceeded, some oil should be removed with the vacuum pump until the ideal level is reached.
| TIP: Take care to use the suitable oil which fits the car. The registration certificate or car manual provides information on this. Wrong power steering oil can affect the hose interior and cause severe damage. Always buy the required amount for one refill. Large and cheap bulk purchase does not make sense because of the long oil change intervals. |
Power steering oil costs 10 – 50 EUR (± £9 – 44) per liter.
The effects of old power steering oil
Contaminated oil in the hydraulic power steering system causes damage to all components. Particularly the power steering pump is significantly affected by particles in the oil flow. The micro- particles often settle in the bearings and cause abrasion. A defective power steering pump causes a loud grinding noise. Its replacement is not difficult, although expensive. A new power steering pump costs 150 – 500 EUR (± £133 – 445), depending on the manufacturer. Fresh oil in the power steering and a new expansion tank extends the life span of the power steering pump at only a fraction of these amounts.
How to dispose of old oil
Like all lubricants, old power oil is chemical waste which cannot be disposed of with the normal household refuse nor poured into the sewer. We recommend pouring the old lubricant in the empty bottle of the new oil and handing it in at the point of purchase of the new oil. Retailers are obliged to accept it as they have partners for the professional processing chemical waste.
Foto: Babich Alexander, Jumnong, CHIEW, Andrey_Popov, Pavel Skopets, dooguzi, Komjomo, Ake Apichai Chumsri, g-stockstudio / shutterstock.com
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