芒果体育

Fixing the Bum Steer

Redesigning the failure-prone Mini Cooper electric power steering pump for greater durability

INNOVATION CASE STUDY    |    

The compact Mini Cooper is a great example of a vehicle that benefits from the advantages of electric power steering assist. Its electro-hydraulic power steering pump is mounted to the front subframe in an otherwise unused space between the engine and the firewall. A horizontally mounted cooling fan pulls air over the pump to keep it cool.

These electric power steering (EPS) systems are more efficient, creating hydraulic pressure only when needed instead of wasting energy by continuously pumping fluid. They also allow for more convenient packaging under the hood; they can be mounted almost anywhere since they don’t rely on a belt-driven pulley mounted on the engine.

This design generally works well, but a pattern of premature pump failures eventually developed as these vehicles gained some age and miles. The cooling fan, it turns out, can become clogged with road debris such as leaves and litter, allowing the pump to run hot.

By examining the failure points, Dorman’s engineers worked on more robust designs for the armature and brushes.

The compact Mini Cooper is a great example of a vehicle that benefits from the advantages of electric power steering assist. Its electro-hydraulic power steering pump is mounted to the front subframe in an otherwise unused space between the engine and the firewall. A horizontally mounted cooling fan pulls air over the pump to keep it cool.

This design generally works well, but a pattern of premature pump failures eventually developed as these vehicles gained some age and miles. The cooling fan, it turns out, can become clogged with road debris such as leaves and litter, allowing the pump to run hot.

Overheated pumps often resulted in excessive wear of the soft copper commutator or the carbon brushes in the electric motor. A groaning noise from the pump is usually the telltale sign of internal wear. Sometimes the motor driver circuit would simply burn out, resulting in no power assist at all. The only remedy for either condition is to replace the pump.

Dorman’s product team noticed the abnormally high failure rate for this part and decided to investigate the root cause before offering a direct replacement. Excessive heat was the culprit, but they realized there was little they could do to prevent the cooling fan from becoming clogged. So instead they chose to focus on making the pump itself more resilient to the effects of heat.

By examining the failure points, Dorman’s engineers worked on more robust designs for the armature and brushes to make them more durable under all conditions. They also discovered that the motor driver circuit was often the victim of heat buildup, so they redesigned it with greater thermal protection.

To ensure an affordable replacement part, Dorman applied all these improvements into the existing original equipment assembly. The result is an OE FIX remanufactured power steering pump (599-950) that looks like the original part, performs like the original part, and installs like the original part right out of the box, but has been thoroughly improved to deliver better-than-original durability. In testing, this upgraded design has proven more reliable, allowing Dorman to place a limited lifetime warranty on it.

“This redesigned pump is the kind of part my customers always appreciated,” says Nick D’Alessio, Master Technician for Dorman’s Proving Grounds testing and validation garage. “They liked the peace of mind that comes from better-engineered products, and they knew I was looking out for them down the road whenever I recommended them.”

To further reduce the chance of similar issues in the future, D’Alessio also recommended replacing the cooling fan, which Dorman produces a direct replacement for (979-750).

“If you’re changing the pump, that fan has probably already had a rough life, too,” D’Alessio said. “If you only have to do the job once, your customers will be even happier.”

Remanufactured Power Steering Pump

599-950
Mini Cooper 2008-02

View Product

Problem:

The original equipment pump overheats when its cooling fan becomes clogged with debris, causing premature internal wear and failure of the motor driver circuit.

Dorman’s redesigned pump features improved carbon brushes and copper armature, and the motor driver circuit has been upgraded to better withstand high temperatures.

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