Heavy steering and power steering fluid loss: is it the hose, the pump or the rack?

Hydraulic power steering turns heavy when its fluid runs low or pump pressure stops reaching the steering gear. The fluid does not use itself up: it leaks from a hose, a connection, the pump or the rack. Electric power steering (EPS) has no fluid and no hoses, so heavy steering there has another cause. First find out which system the car has.

Is the steering hydraulic or electric?

The fluid reservoir settles it: a hydraulic system has power steering fluid and hoses to carry it, an electric one has neither. A training module on steering systems from Turkey’s Ministry of National Education describes the electric type:

“Electronic steering removes the need for a power steering pump and does away with the hoses, the hydraulic fluid and the engine-driven pulley system.”

Turkish Ministry of National Education, Steering Systems module, 2011 (our translation, here and below)

Open the bonnet. The module puts a steering wheel symbol on the reservoir cap; a reservoir means a hydraulic system. That a system without fluid has no reservoir is our inference, not the module’s wording. If you find none, check the owner’s manual.

Where an electric motor drives the pump instead of a belt, the system still runs on fluid: “Both produce hydraulic pressure”, the module says. On an electric system, a steering warning lamp that stays on after the engine starts means a fault.

Why is my steering wheel hard to turn?

On a hydraulic system the wheel gets hard to turn when less pressurised fluid, or none, reaches the steering gear. The car still steers, unassisted. The module names two causes: “If the pump belt breaks or a leak develops in the hydraulic system, the hydraulic assistance in the steering system is lost.”

• Low fluid. If the level gets too low, Larry Carley writes in the US trade magazine Brake & Front End, “the pump may suck in air causing noise and a loss of power assist”.
• The belt. A broken belt ends the assist. A squeal with the wheel cranked to one side “usually indicates a loose or oil-soaked belt”, Carley says.
• A hose breaking up inside. Flakes of rubber, Carley adds, can lodge in the valves of the pump or steering gear; noise and steering effort go up.
• Internal leakage in the rack. With leaking spool valve seals, he writes, the steering “may feel stiff or sluggish especially when a cold vehicle is first started”.
• Outside the hydraulics. For stiff steering the module also lists the steering gear itself, ball joints and too much caster.

Why does the power steering fluid keep going down?

Power steering fluid only goes down when it leaks: from the high-pressure hose, the return hose, their connections, the pump or the steering gear. Carley:

“Normally, the power steering system should not use any fluid. The level should remain the same regardless of the age of the vehicle or how many miles on the odometer -unless, of course, the system is leaking.”

Larry Carley, Brake & Front End, 1 April 2005

A rack, Carley writes, leaks where the rack bar passes through the end seals, at the pinion input shaft seal, or internally in the spool valve housing. An end-seal leak may never reach the ground; the fluid can stay inside the bellows.

In a 2012 defect report to the US regulator NHTSA, Honda wrote of certain 2007 and 2008 Acura TL cars: “Prolonged high under-hood and power steering fluid temperatures may cause the power steering hose to deteriorate prematurely”; the hose can then crack and leak. The remedy was a heat-resistant hose. The finding covers those cars only.

In the UK’s MOT inspection manual for cars, a power steering leak from a failed component, joint or seal is a Major defect, as is an empty reservoir.

How do you spot a leaking power steering hose or pipe?

A leaking steering hose is wet, sweating or cracked. Andrew Markel’s list in Brake & Front End goes further:

• Abrasion. With the outer layers damaged, the inner ones are exposed to heat and chemicals. Find the cause: worn motor mounts, missing mounting tabs, an exhaust gasket leak.
• Bulges, soft spots, cracking. The layers are breaking down. With a bulge, fluid is working between them and “complete failure is imminent”.
• Heavy corrosion on a fitting. A fitting that has lost its coating will eventually fail.
• Grey or black fluid. Rubber or metal particles are in it; the hose’s inner layers may be compromised.

Markel describes high-pressure hoses built “to handle up to 1,500 psi”; return hoses are of a type “tested only to 250 psi” and are typically held by spring clamps. A worm-drive clamp there “may result in a leak as the hose material compresses”.

On steel pipes and connections the module lists three faults: cracking, breaking and working loose. Vibration is the cause; a connection that is not properly secured loosens and seeps. A leaking connection may need new seals or O-rings. Carley warns against trying to stop the leak “by simply tightening the hose or line connection”, which can strip the threads. Freeing a corroded fitting is covered in the seized line nut article.

Is it the pump or the rack?

Noise points to the pump, fluid in the bellows to the rack; check both once the hoses and connections are dry. A pump that whines, Carley writes, has worn-out shaft bearings and needs replacing. But “Groaning noises can be caused by restrictions, low fluid level or air in the system”, so check the fluid first.

On the rack, feel the bellows: squeeze soft rubber ones, unclamp and slide back hard plastic ones. “A few teaspoons of fluid in the bellows of a high mileage vehicle is not unusual”, Carley notes; a lot means a leaking rack. Such a rack is usually replaced complete, not resealed: corrosion or scratches on the rack bar quickly ruin a new seal.

In what order should you check?

1. The system. Is there a fluid reservoir? If not, stop looking for fluid and hoses.
2. Level and colour. The module’s way: engine idling, wheel turned fully left and right a few times, then held straight.
3. Hoses, end to end. Engine running, as the module asks: wetness, sweating, cracks, bulges, rub marks.
4. Connections and pipes. Fluid around the fittings; clamps loose or missing.
5. Belt, bellows, pump. Belt tension, cracks and oil; fluid in the bellows; pump noise.
6. After the repair. The right fluid, bleeding, the level; then check the connections again.

Our sources give no prices; what follows from them is that cost depends on where the leak is: a connection seal and a complete rack are different jobs. Hose replacement and bleeding are covered in the truck steering hose article, and why a hose is not patched in the hydraulic hose repair article.