Foamy power steering fluid is usually accompanied by a heavy feeling steering and a noisy power steering pump. It’s caused by air being sucked into the power steering system through some opening.
Air gets into the system and gets whipped into a foam with the power steering fluid by the vanes of the impeller in the power steering pump. Since the foamy fluid can’t transmit force, your steering becomes heavy.
A power steering system that’s been compromised by an opening that allows air seepage may also cause the power steering fluid reservoir to overflow. Here are some more reasons why your power steering fluid is foamy.
1. Brittle or Cracked Power Steering Hydraulic Seal
Power steering fluid becomes foamy because of air that’s made its way into the system. Your steering wheel is connected to a steering shaft which runs through the dash and down to a gearbox where it joins the power steering system.
Most steering wheel systems in modern cars today are hydraulic. A seal is used to keep power steering fluid from leaking out. The power steering shaft seal is actually two seals comprising of an outer seal designed to prevent dust, dirt and debris from damaging the inner seal. The inner seal is the power steering input shaft seal designed to keep power steering fluid in and provides a second barrier against contaminants entering the power steering system.
Since it’s a component designed to work 24/7, this seal is prone to wear and tear as well as exposure to caustic power steering fluid. Over time, the seal becomes brittle and cracked allowing air to pass into the power steering fluid causing it to become foamy.
2. Issues with the Low-Pressure Return Hose
Although power steering was introduced in automobiles as early as the 1930s, not all cars were equipped with this feature. In fact, my brother’s 1994 Honda Civic DX didn’t come with power steering which made turning at low speeds challenging, especially with bigger-than-factory aftermarket rims.
This lack of power steering is one of the reasons why the diameter of steering wheels prior to the 1980s were bigger than the ones in modern vehicles. The wider diameter provides extra leverage for turning. Below are other components of the steering mechanism that can get compromised creating foamy power steering fluid.
The power steering pump
The power steering pump is an important component to the power steering system – it’s driven by the engine via an accessory belt. The power steering pump is connected to a power steering reservoir which holds power steering fluid. To carry the power steering fluid from the reservoir to the steering box and back to the reservoir, there’s a high and low-pressure hose.
The high-pressure hose is more robust, able to withstand temperatures of over 270 degrees Fahrenheit and pressure of over 1500 PSI: it’s responsible for carrying power steering fluid from the reservoir to the steering box.
But the low-pressure hose is not as robust which is why it’s a common point of failure in a power steering assembly. Its only job is to carry the power steering fluid back to the reservoir. Even though the low-pressure hose doesn’t have to work with as much pressure and heat it can also become worn through use. Sometimes metal flakes and impurities from the worn-out hose causes deterioration. This worn low-pressure hose is what can allow air into the power steering system causing the power steering fluid to foam.
3. Faulty Clamps Between the Pump and Reservoir
Another issue that can cause foamy power steering fluid is if the clamps on those rubber hoses between the reservoir and pump inlet connection have become loose. One of the most overlooked areas of an automobile when it comes to maintenance is the power steering hose. Most people won’t know there’s a problem until something goes wrong.
At least that’s what happened to me with my 2001 Nissan Maxima. Corrosion prevented the clamps from maintaining a firm fit around the hoses. Given the amount of pressure necessary for a power steering system to work, it’s no surprise if air passes through these weakly clamped areas.
4. Leak in Power Steering Pressure
Like many other systems in your car, truck or SUV, the power steering is a closed system. A leak in power steering pressure might also mean a power steering fluid leak. The power steering system works under a great deal of pressure and heat. Over time, the system begins to degrade. As your vehicle collects more miles, the O-rings and seals lose flexibility and tiny bits of the seals we talked about wind up in the fluid. The supply and pressure hoses develop holes as they age.
An aging power steering system can develop numerous breaches that allow the invasion of air into the system causing foamy steering. Some obvious signs is a leak on your parking space. Power steering fluid is highly flammable and can be a hazard if you let it keep leaking on your engine.
You’ll want to check for abrasions or signs of chaffing which can be caused by loose mounts, leaking gaskets from the engine or anything else that can cause damage to the hoses.
5. Puncture in the Pressure Line
If you find evidence of damage to the outside of the hoses, chances are the inner layers are compromised as well. A power steering hose that’s bulging or feels soft are definite signs of deterioration. This is usually a sign that the inner layers of the hose are degrading.
Cracks or obvious holes (especially in the high-pressure line) can introduce air into the power steering system which will cause the power steering fluid to become foamy. If you observe any cracks or obvious holes on the hoses, you’ll want to replace them quickly. Like the E-Gear hoses on a Lamborghini Gallardo, when you do, it’s best to get the high and low-pressure hose replaced at the same time.
6. Cracked Power Steering Reservoir
How do you know if your power steering reservoir is cracked? The most obvious sign of a bad power steering reservoir is leaking power steering fluid. Power steering fluid is clear with an almost amber color that makes it harder to see than other fluids that can leak from your car. As you turn the steering wheel, the power steering pump pushes power steering fluid into the steering gear.
The gear applies pressure that turns the tires. If the leak you’re investigating has a burnt marshmallow smell. There’s a good possibility that the leak is coming from the power steering reservoir. Constant temperature changes will cause deterioration of the power steering reservoir leading to a leak. But if there is a leak, it also means that air can get sucked in causing the power steering fluid to foam.
Old Power Steering Pump
A power steering pump pressurizes power steering fluid. A failing power steering pump will either start to leak; make a whining noise when you turn the wheel; or decrease power steering assistance.
But if you experience an immediate loss of power steering assistance it’s usually a sign of a broken drive belt or loss of steering fluid. An old power steering pump could have fissures that allow air to be sucked into the power steering system causing foamy power steering fluid.
Given their job, power steering pumps are prone to wear out. This is one of the reasons why many new cars are now manufactured with electric power assistance.