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Old 01-17-2013, 04:34 AM   #30
Registered User
Join Date: Jun 2011
Location: Brisbane, Australia
Posts: 347
My Ride: 2007 MX-5
Update: So I pulled the pump off again today ready for the new one. Couldn't help myself and pulled it apart again to see what's going on. You need a #40 Torx bit.

All the impeller blades were free to move except one. I then noticed (under a magnifying glass) that the blades have a rounded edge and a flat edge. The slots are rounded at the axis end and I'd put a couple of blades in the wrong way i.e. rounded edge out. So I cleaned it all up again and reinserted the blades rounded edge in. I went over to Queensland Hydraulic Services who very kindly gave me (no charge) a 64mm ID, 2mm "O" ring for the case. Reassembled the pump.

So, I couldn't help but keep thinking that the problem that arose on the test drive yesterday was an air lock and that the pump was probably working - it did for the first 5 minutes. So I pulled out the reservoir and emptied it out and gave it a wipe.

So far all that this exercise has cost me is my free time, a drive in the MX-5 (hardly a task) over to Salisbury to get the "O" ring and 500 ml of Dex 111. So what's another 500 ml of Dex 111 out of the 4 litres I bought? So I put the pump and reservoir back on, buttoned everything up and filled the reservoir.

Turned the engine over and switched off after a couple of seconds to prime the pump. Re-checked fluid level - small top up needed. Had a beer to think - it was 4:00pm after all. Ran the engine a bit longer, still no weird noises. Checked fluid, had another beer. Drove the car up and down the (double width) driveway and moved it across from side to side without using huge steering angles. No noises, no fluttering through the steering wheel...and we have power steering again! Wooohooo!

Had too many beers by then so will leave the hidden air bubbles to rise overnight and take it on a careful test run tomorrow. Fingers crossed.

Footnote: I think it's pretty poor that a premium Euro car such as the BMW has this sort of failure though. I've seen plenty of cars (Holdens, Falcons, Japanese) that have been driven into the ground - and then another 100,000 km - and the power steering still worked fine and had never been touched. This failure shouldn't happen at 150,000 km in a modern car.
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