Power steering hose for Volkswagen Transporter T4

Three sections, three constraints

• The suction section, between the reservoir and the pump. Pressure is virtually zero, but the hose must withstand the vacuum without collapsing. A softened hose flattens out and the pump draws in air, which will eventually destroy it.
• High pressure, between the pump and the rack. This is the section of the circuit under the greatest strain: a reinforced hose, sometimes crimped onto rigid fittings, designed for high pressures and hot oil.
• The return line, from the steering rack to the reservoir. Low pressure, but high temperature and constant exposure: this is the hose that leaks most often, and is the easiest to replace.

A return hose fitted in place of a high-pressure hose will burst. The reverse is possible but unnecessarily expensive. Identify the section before looking for the part.

Spotting a power-assisted steering leak

• The reservoir level drops without any visible puddles: the leak is often at a fitting, and the oil sprays out as a mist onto hot components.
• A whining noise when turning the wheel, especially when the system is cold and the wheel is turned to full lock: there is air in the system, indicating a suction leak or a low fluid level.
• Intermittent heavy steering, which returns to normal after a few kilometres: typical of a suction hose that collapses.
• A reddish or amber-coloured streak on the rack mount or rack bellows: steering oil can be distinguished from engine oil by its colour and viscosity.
• Foam in the reservoir: a sign that air has been drawn in, not pump wear.

In all these cases, the hose costs a fraction of the price of a pump. It’s best to start there, especially as a pump running dry or with air in the system will eventually wear out completely: a leak left untreated will lead to the breakdown you were fearing.

What to check before ordering

• The two connected components: reservoir to pump, pump to rack, rack to reservoir. This is how these parts are designated, and it is the most reliable way to identify them.
• The type of fitting at each end: push-fit and clamp, banjo with its hollow screw and seals, or screw-in fitting with its sealing cone.
• The routing, as these hoses are pre-formed: the bends, branch connections and mounting brackets are what make them specific.
• Diameter applies only to sections sold by the metre, which concerns only the suction and return lines.

Make sure you have new seals for the banjo fittings: they are single-use, and reusing them is what causes leaks even in a brand-new part.

After replacement, bleed the system

Any opening in the circuit allows air to enter, and a pump that draws in air will quickly fail. Bleeding is therefore the final step, not an option.

With the engine switched off, fill the reservoir with the oil specified for installation, then slowly turn the steering wheel from one stop to the other several times, with the wheels off the ground, topping up the level each time. Then start the engine and repeat the process gently, without holding the steering wheel at either stop for more than a few seconds, until the foam disappears from the reservoir and the whining sound stops. Check the level when the engine is cold the following day: it always drops slightly as the remaining air escapes.