Power steering fluid provides hydraulic assist for the power steering system. Most fluids are either mineral-oil or synthetic oil of some type blended with additives to suppress foaming, prevent corrosion and improve lubrication in the power steering pump and steering gear. Hydraulic power steering systems were used on many vehicles up until the mid-2000s when electric power steering began to replace hydraulic systems. If your vehicle has a hydraulic power steering system, it is important to maintain the fluid and check the level regularly. HOW TO CHECK POWER STEERING FLUID LEVEL First you have to locate the power steering pump and fluid reservoir on your engine. The pump is usually belt driven and located on one side of the engine, with the reservoir mounted on top the pump. On some applications, a remote fluid reservoir is used because there isn't room to mount it on the pump. A remote reservoir is often mounted on the inner fender. If you can't find the power steering fluid reservoir, refer to your vehicle owners manual for its location. Check the fluid level with the engine OFF. Filler Cap for PS fluid reservoir. Wipe any dirt or grease away from the top of the fluid reservoir, then unscrew the cap. The cap may have a dipstick on the underside, or there may be markings on the inside or outside of the reservoir to indicate the FULL level and/or ADD/LOW level. If the level is low, add the specified power steering fluid to bring the level up to the full mark. Fluid expands slightly as it heats up, so there may be FULL markings for HOT or COLD on the dipstick. If it's a really hot day and/or the engine is warm, use the HOT FULL mark. If it's a cold day or the vehicle has not been driven for several hours, use the COLD FULL mark. Avoid overfilling the reservoir as this could force fluid to leak out of the reservoir if there is insufficient head space when the fluid gets hot. Normally, the fluid level should remain constant for many years of service. But as a vehicle ages, leaks may develop causing a slow loss of fluid. If the level gets too low, air can be drawn into the pump, causing noise and/or a reduction in power steering assist. HOW TO CHECK THE CONDITION OF THE POWER STEERING FLUID The color of new power steering fluid will vary depending on the dyes in the product. The fluid may be clear, amber, pink or red. If a normally clear or pink PS fluid has turned dark brown and/or has a burned smell, it is oxidized and needs to be replaced. If the fluid appears foamy, it is aerated. This may be the result of the fluid level getting too low and pulling air into the pump, or it could be the result of a leaky shaft seal that is allowing air to be mixed with the fluid. Foamy fluid can affect power steering assist but has no effect on the condition of the fluid. Checking for trace metals in the fluid: Another method for checking the condition of the fluid as well as condition of the entire power steering system is to use a chemical test strip (such as those available from Acustrip). When the test strip is dipped into the fluid, it changes color to indicate the presence of metal wear particles in the fluid. Elevated levels of certain metals such as copper, iron and nickel in the fluid indicate corrosion and/or wear, and the need for a PS fluid change. POWER STEERING FLUID TYPES Different vehicle applications may require different types of power steering fluid. Some use ATF transmission fluid such as Dexron, Mercon, Type F, ATF+4, etc.) but many newer vehicles use some type of synthetic-based hydraulic fluid that is specifically formulated for power steering use. Synthetic fluids flow well at low temperature, which improves pump lubrication and longevity. Although a "universal" power steering fluid may be satisfactory for many applications, some vehicles do require special additives for seal and pump lubricity, and corrosion protection. A top-off fluid must also be chemically compatible with the PS fluid that is already in the system, and the viscosity of the fluid should meet the requirements of the vehicle manufacturer for proper pump lubrication, power steering feel and assist. European and Japanese vehicles often have their own unique requirements for power steering fluid. Such applications may require a high performance synthetic-based PS fluid that meets DIN 51 524T3 and ISO 7308 standards. Audi, BMW, Mercedes, Porsche, Volkswagen and Volvo all have various power steering fluid requirements which can vary depending on the year/make/model. Many of these applications specify one of several different types of Pentosin power steering fluid. Japanese auto makers such as Honda, Mitsubishi, Nissan, Subaru and Toyota also have their own PS fluid specifications. The type of power steering fluid that is specified for your vehicle should be marked on the PS reservoir or filler cap. You can also find the recommended PS fluid listed in your vehicle owners manual. Use the type of fluid specified (or one that meets the OEM requirements) to reduce the risk of incompatibility issues and problems down the road. Using the wrong type of PS fluid is a common cause of power steering pump failure! Best Advice: If you don't know what type of PS fluid you should use, do NOT add any fluid to the pump reservoir until you can find out the proper type. POWER STEERING FLUID APPLICATIONS For a detailed application chart of power steering fluid recommendations by vehicle manufacturer, Click Here. The following are some general guidelines on power steering fluids (always refer to your vehicle owners manual or the OEM service literature for specifics): Mineral-oil based universal power steering fluids are usually suitable for any of the following: Applications that specify Dexron, Dexron III, Ford Mercon, Ford M2c-138CJ or Type A ATF fluids. This includes most domestic makes (Chrysler, Ford & General Motors) from the 1970s through 1990s, and U.S.-built VW models from 1984 to 1989. Mineral-based universal power steering fluids are usually NOT recommended for applications where special fluids are required such as most 1990 and newer European and Japanese PS systems. Most of these require some type of synthetic-based power steering fluid. Synthetic-based universal power steering fluids are usually suitable for applications that have the following OEM specifications: American Motor Corporation C 4124 BMW 82 11 0 148 132; 83 29 0 429 576; 81 22 1 468 879 & 82 11 1 468 041 Chrysler MS-1872; MS-5931 & MS-9602 Ford M2C138-CJ; ESW-M2C128-C&D; M2C195-A; M2C204-A & M2C33-F GM/Saginaw PSF 9985010; 9985835 & 89021184 Hyundai/Kia PSF-3; PSF-4 & PSF 00232-19017 Mercedes Benz 236.3; 345.0; 001 989 24 03 10; 001 989 24 03 12 & Q 1 32 0001 Mitsubishi Diamond SP III & PS Fluid Navistar TMS 6810 Nissan PSF-II Porsche 000 043 206 56 Saab 93160548; (45) 30 09 800 & 30 32 380 Subaru K0209A0080 Toyota PSF Type EH; P/N 008886-01 Volvo 1161529 & 30741424 VW/Audi TL-52146; G002000; G 004 000 M2; G 004 000 M7 & G 004 000 M8 POWER STEERING FLUID SERVICE INTERVALS Power steering fluid operates in a relatively clean environment so it lasts a long time. Most vehicle manufacturers do not even have a recommended service interval for power steering fluid. Even so, after many chilometri and years of service, wear particles in the steering pump and steering gear can contaminate the fluid. Corrosion inhibitors can also deplete over time, and high underhood temperatures can cause the fluid to oxidize and break down. Replacing the fluid every 5 years or 50,000 chilometri can help prolong the life of the power steering system and reduce the risk of expensive repairs down the road. POWER STEERING FLUSH Some repair facilities recommend a power steering fluid flush for preventive maintenance. The old fluid is flushed out of the power steering system and replaced with new fluid. The fluid should be flushed regardless of time or chilometroage is it is dirty or has been accidentally contaminated with any other fluids (coolant, motor oil, brake fluid, etc.). Flushing is mostly beneficial to newer vehicles with vane-style power steering pumps. These pumps have much tighter tolerances than older roller-style pumps, and can't tolerate contaminants in the fluid. The power steering system should also be flushed if major repairs are being made, such as replacing the power steering pump, hoses or the steering rack or steering gear. Contaminants in the old fluid can damage new parts, and many power steering component suppliers say you must change the fluid if you want to maintain the warranty on your newly installed parts. HOW TO CHANGE POWER STEERING FLUID The easiest way to change the fluid is to disconnect the hoses from the steering gear or rack, and drain the fluid from the power steering reservoir and pump into a container. This still leaves some of the old fluid inside the power steering gear or rack. The trapped fluid can be removed as follows: 1. Reconnect the pressure and return hoses to the rack. 2. Disconnect the return hose at the reservoir, and temporarily plug the return hose opening in the reservoir so fluid can't leak out. 3. Add fresh power steering fluid to the reservoir. 4. Start the engine and allow the pump to push the fresh fluid through the steering gear and rack and out the return hose. Catch the discharged fluid from the return hose in a container. CAUTION: Keep a watchful eye on the fluid level in the reservoir and do NOT let the fluid level get too low. Starving the pump while it is running could damage the pump. An alternative method would be to disable the ignition system and simply crank the engine rather than starting it up. Cranking the engine will drive the PS pump and push fluid through the system. Do NOT crank he engine for more than 30 seconds at a time otherwise you could overheat and damage the starter. Crank for 30 seconds, then wait a minute or so before cranking again. A couple of cycles should do it. Don't overdo it or you will run your battery down. 5. Cycle the steering …

Fonte: AA1Car.com