Automobile maintenance: Power steering fluid

10/01/2011

Pint-for-pint, the one or two quarts of power steering fluid required by your passenger car are probably some of the least appreciated fluids under the hood. Considering what it does, and how much a motorist depends on it, we’re talking about the lifeblood of your steering system. Yet keeping it clean and doing its job doesn’t require all that much effort.

The function of this fluid is basic: transmitting hydraulic pressure to make steering easy—but achieving a seamless system operation over a wide variety of conditions is not. The fluid must perform consistently in any situation, from sub-zero to triple-digit temperatures, and both ambient and under-hood temperatures. It also must function when the engine is at idle or full-throttle, and under high pressure, all the while providing adequate lubrication to pump and control valve assemblies, maintaining integrity of rubber components in the system, and promoting noise-free system operation. And your fluid has to do all of these things over an extensive period of time!

Transfer Tool

Of course, these demands take their toll on the fluid and break it down, which can lead to inconsistent performance and expensive component failure. Although vehicle manufacturers haven’t generally specified in the past when to actually change the fluid, some are doing this now, or they have designed a fluid that they feel will last “the life of the vehicle.” Of course, your opinion on a vehicle’s lifespan may differ from that of the manufacturer. That said, we’ll share a couple of relatively simple and mess-free methods for maintaining the fluid for a much longer period.

If your vehicle’s manufacturer recommends a fluid change interval, definitely follow that. Do-it-yourselfers will need to consult a service manual for the procedure on their particular vehicle. If there is no recommended change interval, however, here’s a good rule of thumb to follow: Change it as often as you would your engine coolant. Power steering fluid of the “long-life” variety should be changed every five years or 100,000 miles.

For conventional fluid, the interval is every three years or 50,000 miles. Most likely, the fluid will appear normal at this point—either amber (on most vehicles) or pink/red in color. This is good, as no serious problems are indicated.

Filler Cap

As with other vehicle fluids, changing before visible deterioration occurs is ideal. The fluid should be checked at every routine service interval, but if at any time before the interval recommended here, it appears significantly darker than new fluid, it should be changed at that time. Use the following easy procedure for evacuation and filling.

Simply withdraw only the fluid that’s readily accessible in its small reservoir, and replace that portion with fresh fluid. You’ll be doing this several times over a week or so until the fluid color looks normal. To use this technique, you first have to acquire the proper tool. It’s sold as a “fluid removal/transfer tool” or battery filler, and resembles a turkey baster (but that’s made of different materials, so don’t use one of those from your kitchen). You’ll also need to purchase the proper type and amount of fluid as indicated in your manual. Older vehicles use automatic transmission fluid, but later-model vehicles use some form of mineral-based fluid with a “universal” type fluid sufficing as a replacement. Other vehicles, such as Honda and Mercedes-Benz, require a very specific type of fluid.

Next, locate the reservoir and remove the filler cap/dipstick. Withdraw what fluid you can with your newfound “fluid removal tool,” being careful not to slop, spritz, or squirt the fluid carelessly on the engine. If you do, immediately and thoroughly clean the spill up with a shop towel. Dispose of the used fluid responsibly, as you would do with used motor oil. Now, fill the reservoir up to the recommended mark on the dipstick (“cold” or “hot”) and then start the engine. Cycle the steering from left to right a couple of times, and do a final check and correction of the level.

Final Check

If the fluid is only somewhat darker than new—but not dark brown—you can perform this procedure on consecutive weekends (or a little more often, if you can’t stand the suspense!) until you get the desired “good as new” fluid appearance. If the fluid is dark brown or black that indicates a serious system contamination (likely due to breakdown of internal rubber parts or hoses) and more extensive repairs are called for. In this case, solvent flushing is not recommended, as it won’t stop the internal breakdown described, and will likely make it worse.

Just as with fluid maintenance for your cooling system and transmission, it’s not necessary to change all of the power steering system’s fluid to keep it in good condition—as long as it’s being done before visible deterioration occurs.

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Changing Your Transmission Fluid

You drive the same route to work every day—same open stretches, same intersections, same stop-and-go. But today there’s a subtle discord in the usual harmony, a blip on your vehicular radar, a bad vibe in your mechanical karma. Shifts seem oddly late and soft. Later, as you pull into the drive, you sense something peculiar. Letting your car idle, you pull the dipstick out of your auto transmission. Fresh automatic transmission fluid (ATF) is bright red and has a distinct petroleum smell. Your dipstick shows a low level, is the color of institutional linoleum and smells like the bottom of a barbecue pit after a biker wedding. Your transmission fluid is badly in need of changing, and the tranny may already be damaged.

Take A Look-See
An overall inspection is the logical first step. A low fluid level may indicate a leak somewhere in the system, possibly at a cooler line that runs to the bottom of the radiator. Find it and fix it, then top up the level. Remember that, unlike the engine crankcase, it only takes about a pint to make the difference between the “Add” and “Full” marks. Also, make sure you use the correct ATF, which we’ll discuss later. If you’re lucky, the lag or shifting problem may just disappear after you add ATF.

The fluid should be bright red, clear and “sweet” smelling. If it’s a smoky dark color, or has a burned odor, a complete change is needed, but the damage may already have been done.

Lockup?
All modern automatics (except for the continuously variable transmissions—CVTs—found on a few late-model cars) have locking torque converters to eliminate slip at cruising speeds, thus saving fuel. These are controlled by the powertrain control module (the engine and transmission management computer) on the basis of speed, temperature, throttle position, etc. If the engine is running at a higher rpm on the highway than usual—300 to 500 more—to maintain the same speed, it’s possible that lockup isn’t occurring. Besides reducing fuel economy, this can have the much more disastrous effect of causing the transmission to overheat.

Check that the transmission converter clutch wire that runs from the harness to the transmission is connected and intact.

Fresh Fluid
The single most important thing you can do to head off big-bucks transmission repairs is to change the ATF on a regular basis.

Some carmakers have backed down from the unrealistic 100,000-mile trans fluid change interval recommended in the past. Every 30,000 miles is much more reasonable. If you tow heavy loads in hot weather, you might even think about annual changes.

Going through the messy operation of dropping the transmission pan and replacing the filter is fine as far as it goes. The trouble is, it doesn’t go far enough. At least half of the old, burned-up ATF and its contaminants remain in the torque converter (the days of those convenient converter drain plugs are long gone), clutch drums, valve body and elsewhere. If you want to get the full benefit from this maintenance service, you’ve got to work a little harder.

Regardless of how far you’re willing to go here, you still must take the transmission pan off, and there are a couple of ways of making this job a little neater. Start by putting the car on sturdy jackstands or, better yet, ramps. Block the rear wheels. If you have a gravel driveway, toss a 4 x 8 sheet of plywood down first to prevent the stands from tunneling into the ground while you’re under the vehicle.

If you just remove the pan (leave a few bolts along one side partway in), ATF will flow out in a wave all around the seam, probably splashing outside the radius of your catch pan. If you’ve got a suitable pump, you can run the pickup hose down into the dipstick tube until it bottoms out, then pump until you stop getting fluid. This will vastly reduce spillage.

To extract as much of the old ATF as possible, leave the pan on, remove a trans cooler line at the radiator, put a drain pan under it, then start the engine for a few seconds to find out which way the fluid is flowing. It doesn’t matter whether you use the inlet or outlet line except that you have to attach a small hose either to the line connector or the radiator outlet in order to collect the ATF. Put the hose into the largest jug you can find, and let the engine idle until air starts spurting. Many professionals enhance this procedure by pouring a few quarts of fresh fluid into the dipstick tube at roughly the same rate that the old fluid is coming out, thus adding flushing action.

Now you can remove the pan. This is not only necessary for changing the filter, but also allows deposits and sediment to be washed out of the pan. There’s another important consideration: This operation provides the opportunity to find out if failure is impending. Judging this is somewhat subjective, so we asked an ASE Certified Master Automotive Technician (CMAT) his opinion.

“You should see next to no swarf or debris, and then only on the first change,” he says. “Subsequent changes should be nearly dead clean. If a newer gearbox is making junk, it’s in trouble. You might find just a trace of aluminum shavings, or other very minor debris, but the assembly process is so clean, and the newer gearboxes so unforgiving of dirt, that any real accumulation generally means a problem is in development.”

Now’s the time to replace the filter and its seal, which probably can be purchased in the same kit as the transmission pan gasket. When reinstalling the pan, start every pan bolt by hand for at least two threads before tightening any of them.

If the last person to install your pan got overly enthusiastic with the wrench, you may find the pan rail has dimples around the bolts. Use a hammer and dolly to flatten them out. Otherwise, the pan gasket will leak. A cork gasket often can benefit from a thin layer of gasket sealer or adhesive, especially to keep it in place while you’re trying to start those first few bolts. Don’t use a thick bead of silicone sealant, as it will squish out between the mating surfaces into little silicone worms, which will eventually break off and clog the pump intake.

Delegate
Of course, you can go to your favorite auto service facility and have a trans flush and refill done. Many shops today have a machine for this purpose, but you’ve got to be sure of what you’re getting. Some quick-lube places will just attach the machine to a cooler line, exchange the fluid, and call it done. We beg to differ. The pan should be removed for cleaning.

The Right Stuff
Most of the automatic transmissions on the road will work just fine on Dexron III/Mercon ATF, except for ’92 and earlier domestic Fords, which need Type F. But the Dexron is essentially a generic fluid, and some experts say they’ve cured shifting problems simply by replacing it with the exact O.E.-specified stuff. They have also confided in us that they’ve inadvertently caused trouble by using bulk ATF that was labeled, “Will also work in …” So, especially with imports, you might want to read your owner’s manual carefully where fluid specifications are listed.

You want real peace of mind? Then think about spending the extra money for synthetic ATF. The master technician mentioned earlier always uses straight $5-per-quart synthetic for his own vehicles.

http://www.popularmechanics.com/cars/how-to/maintenance/1272521

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