Reading through the '5th Annual Minis on The Dragon' forum, 'So what happened to YOUR Mini' thread, I see frequent comment about power steering failures. I understand that these are probably not R56 cars but was wondering if the R56 power steering was the same unit, or design? Any assurances that the R56 will not also have a failure frequency on this Critical function? This is not intended to be a warranty question. ajm

 

The two units are very different and of the same design.

 

The early design is a conventional hydraulic steering rack fed with a hydraulic pump driven by an electric motor There is little difference between this system and one that has an engine-driven power steering pump. The electric motor has it's power 'modulated' according to the amount of assist needed. A steady state cruise on a straight road or sitting in traffic with no steering input lets the pump 'idle down' to save power and to keep it from running hot. Give the wheel a twist and the power to the motor ramps up accordingly. Give the system a reason to keep the power levels up by sawing away at the steering wheel (track days, Dragon) and the system runs much hotter. Couple that with high underhood temps from hard running and maybe even a faulty power steering cooling fan, and the system will overheat and shut down. The shutdown is supposed to protect the system from damage, but it appears that if the system has gone through shutdown, it has already experienced temperatures high enough to start causing damage.

The new system drives the steering rack directly with an electric motor, eliminating the conventional hydraulic system. This allows for greater control of steering feel and power assist. Unlike the previous system, with no power assist needed, the motor is essentially shut off, and not running continuously at partial power. Still, sawing away at the steering wheel will engage the motor more often, draw electric power and create heat. Time will tell how the new system handles such 'abuse'.

The new system isn't untested, GM had a system called 'Magnasteer' for over a decade, and it seems to have scaled well.

Note that if you have wheel alignment issues that cause you to hold the wheel in a certain position to maintain course on a straight road (the car 'pulls' to the left or right), or you have a front-end shimmy, this causes ANY of the above mentioned systems to run in a continuous assist mode and build up heat. Have your alignment fixed to prevent steering system damage.

 

Greatbear,
Thanks

 

Greatbear,
Thanks for the clear easy to understand answer. ajm

 

GreatBear.....it is post like yours that make comming to NAM a good idea.
Thanks