Diagnose power steering noise
Your car’s power steering noise can sound like a whine, growl or squeal. This post will help you diagnose power steering noise. Power steering pumps and steering gears can make a whining sound that is caused by four things:
• low fluid level in the power steering reservoir. When fluid is low is because you have a leak. If you don’t fix the leak, the noise will return.
• air in the system caused by a leak, or a loose or leaking power steering hose or O-ring
• pump is starved for fluid caused by a clogged power steering fluid reservoir screen
• power steering pump is worn
How a power steering pump works
Most car makers use a centrifugal vane style power steering pump. The belt driven portion contains a series of slots with movable vanes. As the center portion spins, centrifugal force throws the vanes outward into the oblong areas of the pump chamber. Each vane pushes a small amount of fluid into a smaller section of the chamber. As the chamber size decreases, the vane is pushed back into its slot. Over time, the worn vanes can cause fluid to leak around the sealing edge, causing the high pressure fluid to escape and cause a power steering whine noise.
But what’s actually causing the noise? Cavitation. The power steering pump’s job is to suck in power steering fluid and raise it’s pressure. The pump is always creating suction when it’s running. But if there’s a restriction in the supply line, the pump creates a vacuum condition. That vacuum is what causes pump cavitation. The vacuum lowers the boiling point of the fluid, turning it from a liquid into gas bubbles. When those bubbles are compressed (pressure rises) the explode as they turn back into a liquid. Exploding bubbles is what causes your power steering whine and power steering growl.
Cavitation damages the pump by erroding the vanes and housing. If you don’t fix the problem, you will destroy your power steering pump.
Check power steering fluid level first
Check for power steering fluid starvation
If your power steering whines when the system is cold but the noise goes away or gets slightly better once it warms up, you may have a fluid starvation problem caused by a clogged reservoir screen/filter. Many newer vehicles have a filter screen in the bottom of the reservoir. As power steering fluid ages, crud can accumulate at the bottom of the reservoir and clog the screen. That causes fluid starvation to the pump so you get a power steering whine when cold. The whining goes away as the fluid heats up and loosens up the crud buildup. But it settles back into the screen when you turn the vehicle off. You can clean some filter screens while others must be replaced. See this post on how to do it on a Chrysler vehicle.
Check and clean the power steering fluid remote reservoir filter screen
If your power steering still makes noise after refilling, check for a clogged filter screen at the bottom the remote power steering fluid reservoir (if your vehicle is equipped with one). You can try cleaning the filter screen. Remove it from the vehicle. Drain it. Spray with brake cleaner and shake while spraying. If you can’t access the screen, replace the entire reservoir.
Check for a slipping belt
If you have a power steering whine or squeal that’s only present when turning, that’s the sign of a slipping belt. If you have an automatic belt tensioner and a multiple ribbed belt, read this post on how to test the automatic tensioner to see if it’s working properly. Replace the tensioner if it fails the test.
If you have a whine when hot condition, this can also be an indication of a slipping belt, a low fluid condition, contaminated fluid, or a sticking pressure relief valve in the pump.
Check the idler if you have a growling noise
Many serpentine belt systems use idler rollers to make sure the belt wrap at least 270° around the power steering pump pulley. The idler roller is supported by a bearing. When that bearing wears, it makes a growling noise. The best way to check the idler roller bearing is to use a mechanic’s stethoscope. See this post for information on how to use a mechanic’s stethoscope to check for worn bearings.
Check for air in the reservoir
Remember those air bubbles I talked about
previously. If you’ve filled the system and cleaned the reservoir screen but still have air bubbles, you’ve got a leak somewhere that’s letting air into the system. The most likely culprit is the return line from the rack. Check for loose hose clamps or deteriorated rubber hose. On some vehicles, the return hose connects to a fitting on the pump that seals with an O-ring (Honda). Replace the O-ring.
Purge the air from the power steering system
If you’ve fixed the leak and still have noise, you’ve got air in the system. The old way to remove air was to turn the steering fully right and then fully left. That procedue allowed pressurized fluid into the chambers of the steering gear and force the air out. But most car makers no longer recommend that procedure because turning the steering wheel to full left and full right (also known as “lock to lock”) causes the power steering pump to create up to 2,000-psi. That high pressure can blow out seals in a rack and pinion steering gear and it can rupture seals in high pressure lines. The new method is to apply vacuum to the fluid reservoir to get rid of the power steering whine.
To do that you’ll need a hand held vacuum pump and some sort of adapter. Apply the adapter to the reservoir and pump the hand held vacuum pump to apply a vacuum to the entire system. Leave it under vacuum for about 5-mins. Then start the vehicle and observe the fluid. If it appears pink and foamy or still has a power steering whine sound, you still have air in the system. Let the bubbles dissipate and try the procedure again later. Find more information here
©, 2015 Rick Muscoplat
Posted on by Rick Muscoplat