I recently bought a 2002 MCS with 50k miles. I have been reading all the stickies and tackling the expected leaks. Of course the sticky about power steering failure and resulting engine fires caught my attention.



I’ve been looking for a definitive description of what causes this failure, but have not found one. I’ve read that the fires are typically caused by a power steering pump getting stuck ON (even with the ignition off) causing a thermal meltdown and electrical fire. But what causes the pump to stick on?



I realize the pump has some electronic circuitry that controls when the pump should run (only as needed), is this circuit the cause of the failures?



I also read somewhere that the power steering cooling fan is not intended to cool the PS fluid or even the pump, but is really there just to keep the control circuitry from overheating.



If the above is correct, than the sequence of extreme power steering failure is –

1. The PS cooling fan fails, probably from accumulated road debris
2. The PS pump control module overheats and fails to correctly control the pump
3. The PS pump get’s stuck ON (probably while parked with no airflow) and the current draw ignites the oil soaked power leads
4. Engine fire

My new to me MCS was not included in the PS recall, the fan and PS pump appear original (no grate over the fan) and the PS system appears to be working flawlessly (except for weeping PS supply hoses).



What preventative maintenance should I do to prevent a PS failure?



I plan to replace the fan with the new genuine MINI PS fan. Has the PS pump and control circuitry been improved? I don’t really want to throw $800 at a new pump, but if it would prevent an engine fire might be worth it…



I also plan to check operation of the PS fan at each engine oil change (run engine and turn on AC to check both radiator fan low speed and PS fan), replace supply hoses and keep system topped up with Pentosin CHF11S.



Good plan?

 

Have you determined that the pump was not replaced in the past relative to the recall?

 

I can't be positive, but the local MINI dealer said my VIN is outside the recall range and that they have no record of the PS pump being worked on.

 

Welcome to NAM. I have been trying to understand the underlaying cause(s) for the electrical-hydraulic power steering failure that led to the recall, but I found no reliable information. I pondered on the same questions you raised and I too suspect road debris and difficult winter condition are likely to precipitate the ultimate power steering failure, starting with the cooling fan stops to cool the pump motor and perhaps the integrated control electronics.

Since your VIN is outside the recall, I would just monitor the cooling fan during periodic maintenance. I see no reason to change the fluid except to ensure it does not drop below the minimum limit.

 

I’ve read the issue with the PS pump getting stuck on might be because the circuit board isn’t sealed and dust from the worn brushes covers the electronics causing intermittent steering or a short. Here are some threads with info:

https://www.northamericanmotoring.co...ml#post3197353

Mini Cooper S (R53): Power Steering Pump/Fan/Duct Installation

 

I only glanced at the posts and photos. 183 k miles is a lot to ask of a DC brush motor that has to run all that time. Nothing last forever. Just look at that brush debris.

To me I am impressed with how reliable that motor was. Hay, I am typically contrarian.

 

That is really interesting about the brush dust. Sounds like something worth investigating with a higher millage MINI.

I had a chance today to check out the function of my fans -

* With the engine at operating temp and the hood open I can hear the radiator fan fairly well and feel the air blowing through the radiator. After a couple minutes the fan stops spinning and I can visually see it is stopped (takes a bit to wind down). If I put on the AC, the fan starts back up after a couple seconds (sounds like it starts exactly when the AC compressor engages). No sign of two speeds. Looks like I lost my low speed and need a new fan assy.

* I didn't have the car on a lift, but with a flashlight I could lay down in front of the car and see the power steering fan. At no point did I see the power steering fan move. It spins freely by hand, but did not power up while I was watching. I have a new one that I will install tomorrow.

I read something about the loss of the low speed of the radiator fan is responsible for some of the power steering fan problems, but do not really understand the relationship. I thought the PS fan came on with the rad fan HIGH speed...

 

Even at low speed the coolant fan is quite loud. You may have witness only the fan at low speed. If you suspect your low speed is bad, just take a DMM and measure the resistance at the three pin connector on the right side of the radiator. Check both Hi and Lo with respect to the ground pin. Both should read no more than a few ohms to literally dead short. If so the chance is both speeds are good.

I am under the impression that when the coolant fan is on at high speed, the power steering fan does not run - as there is enough air moving pass the pump.

 

From what I've been told by an ex-mini tech was the compounding of issues in the system.

Leaks / Low fluid level can cause the pump to overheat which draws to high of amperage and causes the control circuit to fail sticking the pump on and giving the perfect fuel for a fire.

The cooling fan not functioning (debris or oil contamination) helping cause the above issue.

 

Spent the day yesterday changing power steering return/supply hoses, PS fan, thermostat and housing, CPS O-ring and rear pads and rotors.

Before starting the repairs I had the car on jackstands and ran it up to operating temp. Radiator fan kicked on but no PS fan, placed a beach towel over the front of the radiator and within a minute high speed came on and the PS fan with it. Guess everything is working as it should be...

 

In my 2005 the PS fan actually started to make a very loud grinding noise. I bought a new fan for about $110 from the dealership. When I was replacing the PS fan, a large amount of gravel came out of it. The grinding noise. I replaced the fan anyway. When I crawled out from under the car I found a bottle of canned air and hit it with a few shots. Dust and debris came out and the fan spun freely with out any grinding. I suspect that the old fan, which is sitting on a shelf, is just fine and I now had a spare. In my 2004 Justa. The fan died and then the pump died and Madness Motor works replaced it for about $1100 then MINI sent me a check for about $1100 after the recall was done, then Madness and I had an argument about the quality of work they did and now I go somewhere else. "New" PS pump and fan still work just fine several years on.