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Old 02-01-2011, 04:33 PM   #1
Scooby Specialist
Member#: 95901
Join Date: Sep 2005
Chapter/Region: SWIC
Location: Las Vegas, USA
Default DIY: Power Steering Pump Rebuild

UPDATED master O-ring replacement list in post #9

I own a 80000+ mile WRX. Love it. Paid for, turbo, lots o' space and light. I always check my fluid levels on every fuel fill-up and noticed 4 weeks ago that the Automatic Transmission Fluid (ATF) in the power steering pump reservoir was down to the "Min" line. I filled it back up to "Max" line, and drove away thinking nothing of it.

Week later, I'm notice drips and small puddles of fluid on the garage floor and driveway.

Open the hood and the ATF is down to the "Min" level again. My shiny pulleys mock me.

After a bit more looking I see what looks like ATF (because it's red) on the top of the engine block right behind the PS Pump caught in the ribs of the block casting. I also see it pooling in the area just in front of the PCV valve (no photo). The above photo was taken only 2 days after soaking up the fluid that was there from before.

Also see fluid on the timing cover just under the PS pump. I don't have a photo but I've seen fluid dripping off the oil filter.

Looking at the PS pump itself I notice red fluid on top of it in a little recess. This is right on the parting line between the two halves of the pump. This photo was taken leaning over the engine with my head near the intercooler looking toward the front of the car.

I call Ken up at my local Subaru and ask for a rebuild kit. Ken quotes me a price well over $400. $400, for a rebuild kit?! Oh no sir. Your pump is unserviceable. That's the price for a new one. Ken's a good guy so I thank him for his time and hang up.

Look up the price of a rebuilt one from Rockauto. $122 if you exchange it with your core. $162 w/o core exchange.

To the web! Turns out a few guys have successfully serviced the unserviceable PS pump that we share. Big thanks to Maxxell and his thread over on IWSti and Hwy61 and this thread here. So if you own one of the following this post might be for you:

SAAB 9-2X AERO (2005, 2006)
SUBARU IMPREZA WRX (2004, 2005, 2006, 2007) <-----me
SUBARU IMPREZA WRX STI (2004, 2005, 2006)

Based on Maxxel and Hwy61 measurements I've ordered three new o-rings from McMaster-Carr.

I decided to get upgraded FEP-encapsulated O-rings because McMaster-Carr had four materials that rated "Excellent" for hydraulic fluid resistance and FEP was the cheapest in the sizes recommended in those two threads. ATF is a type of hydraulic fluid. Kalrez Perfluoroelastomer O-rings were also recommended, but at $180 per ring I passed.

I ordered part numbers:
9319K165 Fep-encapsulated Silicone O-ring As568a Dash Number 040
9319K15 Fep-encapsulated Silicone O-ring As568a Dash Number 015
9319K14 Fep-encapsulated Silicone O-ring As568a Dash Number 014

For all three it ran me about $13. A bit spendy for O-rings but these FEP rings rate better than Buna-N which is probably what is in the pump now and failing. Apparently they suffer virtually no expansion when exposed to hydraulic fluid and are good up to 400 degrees F.

Come to find out o-ring sizes are measured in "Dash Number". So while you can order them by dimension, dash number will get you there faster.
Dash Number 040 is the big ring (~ 3" OD x 2-7/8" ID x 1/16" thick)
Dash Number 015 is smaller ring inside the pump (~ 11/16" OD x 9/16" ID x 1/16" thick)
Dash Number 014 is the ring that easy to get to on top of the pump ( ~16mm OD x 11mm ID x 2.5mm thick)
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Last edited by 68Cadillac; 01-23-2014 at 07:55 PM. Reason: Rehosted images
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