Why has my power steering gone heavy?

Why steering suddenly needs both arms, how to tell a hydraulic fault from an electric one, and the two versions of this that mean stop rather than carry on.

Difficulty: beginner
Time: 12 min
Read: 5 min
Safety: warning

Short answer

First find out which kind of system you have. On an older car with a belt-driven pump and a fluid reservoir, heavy steering usually means low fluid, a slipping or snapped belt, or a failing pump — check the reservoir cold and look for a leak. On a modern car with electric assistance there is no fluid to check: it is an electrical fault, often triggered by low battery voltage, and needs the codes reading. Assistance that comes and goes is a fault developing, not a quirk.

Almost every car sold in the last fifteen years uses electric power steering — a motor on the column or the rack, drawing from the car's electrics, with no fluid and no belt. Before that, most used hydraulic assistance: a pump driven by the auxiliary belt, pushing fluid through a rack. The two fail in completely different ways and are confused constantly, which is why the first question is always which one you have. If there is a reservoir with a steering wheel symbol on the cap, it is hydraulic. If there is no reservoir anywhere and the warning symbol is a steering wheel with an exclamation mark, it is electric.

Safety

A car with no power assistance is still steerable but takes far more effort, and the effort arrives without warning at low speed — in a car park, at a junction, pulling out of a drive. If assistance fails while you are moving, keep both hands on the wheel, slow down gradually and pull over somewhere safe rather than trying to complete a manoeuvre. Never keep driving a car with a hydraulic system that has run dry: the pump destroys itself in minutes.

Step by step

Work out which system the car has.Open the bonnet with the engine off and cold and look for a small reservoir with a steering wheel embossed on the cap, usually with a belt-driven pump near it. No reservoir means electric assistance. Your handbook confirms it in a line.
On a hydraulic system, check the fluid level cold.There will be minimum and maximum marks, and often hot and cold ranges. Low fluid is the single most common cause of heavy steering, and fluid does not get used — if it is low, it has leaked. Use the exact fluid the handbook names; the wrong one attacks the seals.
Look for where it went.Reddish or amber oily patches on the drive, wet hoses, or a wet band across the front of the rack behind the engine. A rack leaking at its ends often shows as an oily, gritty concertina boot. Topping up without finding the leak just delays the same failure.
Listen while turning the wheel with the engine running.A whine or groan that rises as you turn, particularly at full lock, is the classic hydraulic pump complaint — usually low fluid, air in the system or a failing pump. A pump that is starved makes this noise shortly before it fails altogether.
On any car, look at the auxiliary belt if you can see it.A belt that is glazed, cracked or hanging loose will not drive a hydraulic pump properly. It usually also drives the alternator and the water pump, so a snapped belt means heavy steering, a battery light and rising temperature all at once — that combination means stop.
On an electric system, check the battery first.Electric power steering draws a serious current, and many cars simply switch it off when system voltage drops. Heavy steering that appeared alongside a slow crank, dim lights or several unrelated warnings is a battery or charging problem, not a steering one.
Notice whether it comes back after a restart.Electric systems that overheat during a lot of full-lock parking manoeuvres will reduce assistance to protect the motor, then restore it once things cool. That is designed behaviour. Assistance that fails and stays failed is a fault.
Get the codes read rather than guessing on an electric system.There is nothing useful to check by hand. The module stores why it shut down — torque sensor, motor, supply voltage, communication with the stability control — and that determines whether this is a connector or a rack.

Common mistakes

Topping up hydraulic fluid and calling it fixed — The system is sealed. A low level means it is leaking, and the next time it runs low may be while you are moving. Find the leak.
Holding the wheel at full lock on a hydraulic system — At full lock the pump is dumping over a pressure relief valve and the fluid heats rapidly. Holding it there for more than a moment cooks the fluid and shortens the pump's life. Back off a fraction from the stop.

If it doesn't work

Heavy only when cold, normal once warm

Cause: Thickened fluid moving badly through a partly blocked system, or a pump on the way out — Fix: Get the fluid condition checked. Dark, burnt-smelling hydraulic fluid has usually been overheated and is a sign the pump has been working hard.

Heavy one way but not the other

Cause: Internal fault in the rack or a failing valve — Fix: Garage job, and worth prompt attention. Uneven assistance is unsettling in an emergency manoeuvre.

Went heavy at the same moment as the battery light came on

Cause: The auxiliary belt has snapped or come off — Fix: Stop. The same belt almost always drives the water pump, so the engine will overheat within a few miles as well as flattening the battery.

Assistance cuts out in slow car park manoeuvres and returns later

Cause: Thermal protection on an electric system, or a marginal battery — Fix: Have the battery and charging tested first — it is the cheaper of the two and the more common. Persistent thermal cut-outs on a healthy battery need the codes reading.

Steering light on but the steering feels completely normal

Cause: A stored fault, often the steering angle sensor after alignment or a battery disconnection — Fix: Usually a recalibration with a diagnostic tool rather than a part. Ask for it to be re-zeroed before agreeing to anything larger.

Questions people ask

Can I drive a car with no power steering?

You can, but it takes real physical effort at parking speeds and the change is abrupt. Get it home or to a garage on quiet roads, and plan your manoeuvres — do not attempt a tight multi-point turn in traffic. If the cause is a snapped belt or an empty hydraulic system, do not drive it at all.

Is electric power steering worse than hydraulic?

It is more efficient, needs no fluid and no belt, and lets manufacturers add parking assistance and lane keeping. Enthusiasts argue it feels less connected. From an ownership point of view it removes an entire category of leak and is generally more reliable.

Why does the steering only feel heavy when parking?

Because assistance matters most at low speed and full lock, where the tyres are being scrubbed sideways against the ground. Most systems deliberately reduce assistance at speed for stability, so a marginal system feels fine on the motorway and terrible in a car park.