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Power Steering – a simple fluid that can cause so much damage! It’s surprising that there are so many different types of fluid and most people have no idea what type is in their power steering system.
What Power Steering Fluid Actually Is
Power steering fluid is a type of hydraulic oil. It is not to be confused with oil for your car’s engine, oil for your car’s gearbox or even with brake fluid. A hydraulic oil for high pressure applications, power steering fluid contains additives to protect seals and to reduce wear. Some of these additives will also counteract the effects of heat generated by the steering pump.
Why the Wrong Fluid Causes Damage
Sometimes confusion can arise when it comes to using different types of fluid. Some older cars have specified the use of ATF (automatic transmission fluid) and as long as the correct specification is used, then this is usually okay. However, the seals in power steering systems are designed to work with dedicated power steering fluid, and using any other type of fluid can cause them to swell and degrade rapidly. Brake fluid, on the other hand, is far worse than ATF and can strip rubber components quickly. In fact, using brake fluid in a power steering system can cause serious damage, including the complete destruction of a steering pump internally.
Finding the Correct Spec for Your Car
You can find the correct fluid for your power steering system in your owner’s manual or on the reservoir cap of your power steering system. Most power steering systems use Pentosin CHF 11S fluid. Some older models use Dexron III ATF. There are many different brands of fluid for power steering systems. A useful reference for Steering Pump is https://westernpowersteering.co.uk/steering-parts/pump/.
Mineral or Synthetic
Most modern power steering units are filled with a mineral-based lubricant and will use a synthetic lubricant in later models. Avoid mixing a mineral-based lubricant with a synthetic lubricant as this can create problems with foaming in the system and also reduce the lubrication in the pump. It is advisable to carry out a complete flush of the system and then top up with the correct lubricant.
Topping Up Correctly
When topping up you must use a clean dedicated funnel and wipe the reservoir cap before removing it. You must then add the fluid slowly in small quantities, checking the level in the reservoir against the min and max marks on the side. Never over fill the reservoir.
When to Change Rather Than Top Up
A top-up is usually used for adding small quantities of new fluid to a reservoir that has leaked. If the fluid in your reservoir is discoloured, darker than normal, or has started to go frothy then you should change the lot. Old fluid in a power steering system has long since stopped providing any protection to seals and wear surfaces and will continue to allow further damage as you continue to use it.
One of the easiest ways to extend the life of your power steering system is by getting the right fluid in it.
