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Old 01-16-2013, 04:14 AM   #27
Brissyjohn
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Join Date: Jun 2011
Location: Brisbane, Australia
Posts: 345
My Ride: 2003 325ti
Well, I put this pump back on today to see how it would go. It worked! for about 5 minutes on a test drive and then the system started having whines and rumbles when any power assist was required. It was worth a try and at least, for me, shows why/how the pumps fail.

So it looks like the impeller/pressure chamber design is the cause of the failures. It seems to me that microscopic particle build up on the impeller causes the vanes:

1. to jam closed - no sheared shaft but no pressure; or
2. to jam open - rotor jams and shaft shears as it is designed to do at the weak point where the rotor fits.

I guess this reinforces the notion that it's worth flushing the PS system every 25,000 km or so to reduce/prevent particulate build up.

I'll get a new pump tomorrow and hopefully fix the PS on my car for another 150,000 km.
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Last edited by Brissyjohn; 01-16-2013 at 04:16 AM.
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