Turning muscle in steering systems

Power steering more than comes in handy. And it quickly is noticed when it's gone.

underhood power steering power steering leaks power steering problems repair shop training technician training A/C training automotive aftermarket In the days of buckboard wagons, the front axle was angled by default as the horses changed direction, and Henry Ford's Quadricycle, built in 1896, was outfitted with a knobbed lever connected to the steering axle that provided the driver with steering control. That arrangement was vaguely like the snazzy red Radio Flyer wagon many of us played with as kids.

One source credits the hot rodders of the 1950s and '60s with many of the developments in the steering systems OEM engineers used beginning in the mid-20th century. There was a time when a teenage hobbyist could buy a used Model T for $35, remove the hood and stuff the frame with a souped up powertrain and wheels to convert it to a T-bucket roadster. To deal with steering and handling of these old boxes, many hot rodders salvaged steering and suspension components from dead pickup trucks and cars and handily adapted them for their own purposes.

Those guys were learning on the fly and they were pretty sharp. Just try to build a go-cart from the ground up and you'll find out just how complicated steering geometry can be, particularly with suspension factored in.

For just one example, the front wheels have to toe out on turns in both directions, because the inner wheel is making a tighter circle than the outer one during a turn. That means the inside wheel has to turn at a sharper angle than the outside wheel needs to turn.

And that is no matter which way the vehicle is turning.

A car without power steering has a more vertical caster angle than a power steering equipped vehicle, which makes the steering easier, but tends to be a bit less stable and less roady during high-speed turns. With the caster more positive (steering axis tilted back at the top), the car typically drives better, but the wheels are harder to turn during low speed maneuvers, and power steering gives the driver more muscle.

Hydraulic Help

The standard fare for power steering was, for many years, a one-piece pump with an integral reservoir. The hydraulic pump most commonly is a belt-driven positive displacement vane pump with a flow control valve at its outlet, a pressure line carrying about 1,400 pounds of pressure to the steering gear and a return line from the steering gear to the reservoir. The steering gear utilizes a spool valve to direct the pressure available to hydraulically assist the driver in turning the wheels.

The old steering gearbox we were so accustomed to before rack and pinion designs became prevalent was fairly reliable, but tended to be heavy and somewhat prone to wear and fluid leakage. A very large and peculiarly designed nut provided the connection between the steering wheel and the turning wheels, but with recirculating steel balls providing the contact for smooth operation.

When the driver turns the wheel, the heavy teeth on this ball nut engage the radially toothed pitman arm gear, which turns the pitman shaft and the pitman arm in an arc that provides steering movement through linkage to the wheel spindles.

The ball nut/rack in this old-fashioned steering gear has sealed hydraulic chambers on both ends that receive power steering fluid pressure from the pump as the spool valve directs. When the driver turns the wheels one way or the other, the spool valve connected to the steering column directs hydraulic pressure to the appropriate side of the steering gear rack to provide hydraulic steering assist.

As the steering gear wears out, steering play increases, so the pitman gear, which is slightly tapered, can be moved into closer contact with the rack using a lock-nutted adjustment screw.

Rack and pinion steering also can be either power or manual, and the steering column is directly geared to the rack that turns the wheels. On these, the power steering pump sends fluid pressure to a spool valve as well and there is sealed flange attached to the steering rack that travels inside a polished bore in the steering gear housing.

Each end of the steering rack is attached to a tie rod with a ball socket, the opposite end of each tie rod connected to the spindle arm so as to turn the wheels on their axes. Fluid directed to one side or the other of the rack's sealed flange provides the assist.

Rubber accordion style boots on each end of the assembly protect the rack (which is a polished shaft with teeth on one side) and in some cases a long metal tube travels from one boot to the other to transfer air from one boot to the other when the wheels are turned. If you see fluid in either of the accordion boots it means the rack is leaking internally and needs to be resealed or replaced. The boots obviously need to be replaced if ruptured, and on high mileage cars they might be damaged and compromised by engine oil or dry-rot.

While power assist is important during parking lot maneuvers, too much power assist at road speed tends to make the vehicle feel kind of squirrelly. Computer-controlled variable assist hydraulic power steering became very common in the 1990s and is standard equipment on higher end vehicles today.

There are about 10 different ways variable steering assist is handled, some at the gear and some at the power steering pump. If you see wires going to the power steering pump at the pressure line connection or to the spool valve area of the steering gear, you typically have computer controlled variable assist power steering, and every vehicle has a different set of diagnostics for that.

When variable assist power steering fails, some of those systems are engineered to provide maximum assist and others are engineered to do just the opposite. I saw this first hand when many years ago, a gas station mechanic in the town where I work connected the battery backwards on a 1998 Ford Taurus.

That maneuver fried the GEM module and some other things. Along with everything else that died because of that fried GEM, that Taurus defaulted to minimum power assist when the GEM went down.

What You Can DoIf you're looking for a power steering leak, start by having an assistant turn the wheels. If the pressure line is leaking it will squirt fluid, so watch for that and wear your safety glasses. Some power steering pressure lines are a pain in the fanny to replace and every technician needs a good set of crow foot line wrenches. Some pressure lines are long and convoluted so as to cool the fluid en route.

Once on a Lexus SC300, we found a leaking power steering pressure hose, and when I called the Lexus dealership I found that the cost of a new line was a gut wrenching $450!

Removing the long pressure hose with its crookedly piped ends and sending it to the parts store for re-rubbering turned out to be a disaster, because the standard power steering line is 10 mm and this Lexus line was 11 mm, which befuddled the parts guy, but it wasn't hard to remedy. I crocus-clothed the line down to a smooth round 10 mm so the ferrels and nuts would work and we fixed that power steering line in short order.

The pulley on just about all power steering pumps requires a special puller. A good one costs about $60, but you can buy a decent one for less than $20 on Amazon.com. Because of the variability in the field, some pulleys require more effort than others to remove. It's a press fit, and they're all tough, so always grease the threads on your pump pulley puller or it might weld itself together.

I've seen it happen more than once, and when that jackscrew stops turning on dry threads you have one piece of metal that used to be two. The pump shaft itself has threads tapped in the hollow end of it for pulling the pulley back on (the pulley tool has adapters that screw into those threads), but sometimes the threads are filled with rust and will need to be chased with an appropriate tap. Just make sure you use the right tap!

Turning the wheels on a Ford car without the engine started causes the reservoir level to spike to the point that it shoves the power steering reservoir cap off and squirts fluid everywhere on that side of the engine compartment. Just about everybody who has pushed a Ford into the shop has seen this happen. It also can suck air into the system, resulting in a steering shudder at low speeds your customer shouldn't be the first to notice.

Asian and European automakers have used remotely mounted power steering reservoirs for years (most domestic nameplates have them now as well), and sometimes the power steering will be noisy and not much help turning the wheels because of a clogged screen in the bottom of the reservoir that many techs don't know exists. Typically, the confused tech will replace the pump for noise and/or lack of power assist to no avail and then call for the calf rope. I've seen it a few times and I've had people call me about it.

Remove the reservoir and clean the screen, reinstall, refill and bleed, and you're back in business. As for noise, don't be fooled by those odd belts that look like Gatorback™ belts but are shiny on their traction surfaces when they're new. They can make a nasty whine that can cause a technician to replace multiple components including the power steering pump. I've seen it happen again and again.

Going Beyond OEM Recommendations

Because power steering fluid gets dirty over time, power steering flushing is a good thing to do every few years even though most maintenance tables don't have an interval for it. Some OEM shop manuals (such as GM) have a procedure for it. Here is how you do the flush.

Raise the front end of the vehicle until the tires and wheels turn freely.
Remove the fluid return hose from the power steering pump reservoir inlet connection.
Place a suitable container under the fluid return hose to collect the old fluid.
Plug the reservoir return hose inlet connection on the power steering pump so it doesn't leak.
With the key on engine off, turn the steering wheel fully to the left and to the right while your helper maintains the fluid level in the reservoir. Continue until the fluid from the return hose runs clear. This step may require up to four quarts of power steering fluid, sometimes more.

It doesn't cost much to perform the above steps, and it isn't hard to do. Oil change outlets charge a fairly heavy price for this very simple operation, so it might be something you want to add as an upsell. It's a legit repair and very necessary but often overlooked.

Then there's the bleeding process. Most of us just dump the fluid in there and turn the wheels back and forth until the whining goes away and foamy fluid stops appearing in the reservoir, but here's the right way to do it and some readers may be surprised.

Raise the vehicle until the front wheels are off the ground.
With the engine OFF, turn the steering wheel from stop to stop 12 times (Ford says to crank but not start the engine during this procedure). Vehicles equipped with brake hydro-boost systems or longer power steering hoses may require turns up to 15 to 20 stop to stops.
Verify power steering fluid level per operating specification.
Start the engine. Rotate steering wheel from left to right. Check for sign of cavitation or fluid aeration (pump noise/whining).
Verify the fluid level. Repeat the bleed procedure, if necessary.

In some cases where cavitation related whining or growling might be a persistent problem, you might try applying 20 inches of vacuum to the reservoir chamber while turning the wheels from stop to stop with the engine running (raise the wheels off the floor). Sometimes this will draw out the problem-causing air bubbles.

Kent Moore makes a $60 adapter for this (No. J-43485 Power Steering Bleeder Adapter), but we built one for GM cars out of a new rubber oil filler cap (the one for an old small block Chevy 350) for a lot less money than that cost.

A few months ago a woman who works in our front office took her Impala to a couple of shops (including the local dealership) for a whining noise in the power steering. The dealership wasn't much help at all, and the shop gave her an estimate to replace the power steering pump in spite of the GM TSB (08-02-32-004B) that outlines the vacuum bleeding procedure.

We fabricated the bleeding tool with a piece of clear hose, a barbed brass connector and the rubber oil filler cap. Using the vacuum chamber that comes with hand held vacuum pumps, we installed the rubber cap on the Impala's reservoir and connected the hose to engine vacuum. After a minute or two of turning the wheels with the engine running, we had taken care of the whining problem without replacing the power steering pump. (Editor's note: This method and more is featured in the August edition of How2, online at MotorAge.com.)

Finally, when it comes to GM cars, I've seen failed power steering pumps that had plenty of fluid but were spinning noiselessly yet not producing any pressure, so look for that. Usually the flow control valve on those units is stuck in the bottom of its bore and is practically impossible to remove. Power steering work isn't rocket science, but doing it well is what we should all strive to do.

Richard McCuistian is an ASE-certified Master Auto Technician and was a professional mechanic for more than 25 years. Richard is now an auto mechanics instructor at LBW Community College/MacArthur Campus in Opp, Ala. Email him at [email protected].