Power Steering Flushing & Bleeding Procedures?

Is there a problem you're trying to solve? Power steering systems typically get ignored because they don't require regular maintenance. Most commonly we do need to bleed the system after repairing a leak. In most cases that involves turning the steering wheel to full-left, then to full-right a couple of times with the engine running. The reservoir must be kept filled to prevent the pump from drawing in more air. In a few models, particularly with rack and pinion steering gears, it can be helpful to drive one front tire up onto a curb or on anything that will make one side higher than the other. If you don't do that, what little air might be trapped in the gear will work its way out over time. Recheck the level in the reservoir after a day or two.

To flush the system, probably the best way to do that is to remove the low-pressure return hose from the reservoir and run it into a container. That way fluid will only flow when the steering wheel is turned, giving you control to prevent running the pump empty. Keep adding new fluid so the pump doesn't draw in air.

To identify the hoses at the pump and reservoir, the high-pressure hose will have a crimped metal sleeve over the end of the rubber hose where a metal tube ends with a soft metal nut. The low-pressure return hose is usually just a rubber hose slid over a tube on the reservoir, and held on with a simple spring-type hose clamp.

There's some special considerations for Ford vehicles. First, it is extremely important to not allow any air to enter the system. This can't be avoided when replacing hoses or steering gears, so there are a number of special tools available to reduce the frustration of bleeding. One of the more popular ones is a funnel designed to snap onto the reservoir. That funnel can be kept over-full to allow air bubbles to burp out while preventing air from entering. The air pockets floating out tend to splash power steering fluid out too. That's what makes it next to impossible to keep the reservoir full. The splashed fluid stays in the funnel, then runs back into the reservoir instead of all over the engine and onto the floor. There are also vacuum pump tools designed to put the power steering fluid under a vacuum to cause trapped air to expand and come out easier, but I haven't had much luck with those.

The problem with trying to burp the system like we do with other brands, by just putting the cap on the reservoir and running the steering wheel back and forth, is so much air burps out of the steering gear that it lowers the fluid level in the reservoir until the pump just draws the air back in again. Even with the funnel, it's not unheard of for it to take an hour or two to get most of the air out.

Some people say they've had success bleeding out most of the air on Fords by raising the front tires off the ground, then turning the steering wheel back and forth with the engine off. This way the fluid is not under pressure. That keeps the air in the system from being compressed. You still won't get all of the air out, but it may be enough that you only need to top off a little a day or two later.

There's one more note that to my knowledge, only pertains to Ford models. If you do need to remove either hose from the steering gear, most of them are held on with a soft metal nut, but that doesn't do the sealing. There's a rubber O-ring on the end of the metal pipe that does the sealing. When the nut is tight, that pipe can still swivel and feel loose. That is normal and acceptable. The O-ring is a common source of leakage so new hoses and new steering gears come with new O-rings. What causes many people to be needlessly concerned is over time, the old pipe corroded to the nut and no longer swivels freely. When reinstalled, the hose does swivel, making it appear to be not fully tightened.