There is not a deducted Technical section for this topic, so........
Tme for a talk about Power Steering Pumps. After rebuilding as many as we have we get to see things…….
Today, we opened-up an exchange power steering pump return received from William out Mount Gravatt way. Beautiful condition pump, near new looking internals, shame that the front oil seal leaked and took out the ball bearing behind the pulley on the power steering pump.
Subaru use SHOWA brand power steering pumps on most all turbo engines. There are two model configurations, one with the high-pressure outlet pointing upwards (which we refer to as Top-Outlet) and the other with the high-pressure outlet pointing horizontally sideways (which we refer to as Side-Outlet). The top-outlet pumps were used on the 2.0 litre WRX and the side-outlet pumps mainly used on the 2.5 litre WRX& STI, the BL/BP Liberty/Legacy/Outback Turbos and the later 2.5 litre Turbo Foresters. William’s exchange return is a top-outlet SHOWA power steering pump.
As stated, it was a shame to see a good condition pump requiring replacement with such little wear. The most common failure mode for the SHOWA power steering pumps is by failure of the front oil seal. When the oil seal leaks the leaking fluid passes through the ball bearing, washing out the bearing lubricant in the process and making the bearing run “dry” and sing its head off.
There are two failure mechanisms that we can see for the premature failure of the front oil seal. One is that the oil seal is located behind the ball bearing and is shielded from airflow that may otherwise regulate the oil seal’s temperature rise. The second is what we find disturbing from a product quality perspective, is that the oil seal is not pressed “home” at the factory. In the case of William’s power steering pump, the oil seal was in contact with the rear metal shield of the ball bearing. The heat produced from the bearing is transferred into the oil seal through its contact with the shield and the rubber in the oil seal deteriorates at an accelerated rate.
When we rebuild a power steering pump the new oil seal is pushed in by hand force only (I have strong thumbs) and pushed home. Clearance to the bearing is confirmed before inserting the shaft with new bearing.
Enjoy!
MORE:
William’s power steering pump is going through the refurbishment process right now.
Internal clearance has been adjusted from 0.015mm to 0.020mm.
The inner side plate has had 0.005mm polished from the face to remove all vane marks. The rear cover has also had 0.005mm polished from the face to remove all vane marks. Flatness has been confirmed by the Johansson gauge method. Note: 0.005mm is the limit of our measurement accuracy.
The power steering pump has been test assembled and the modulating cam ring is articulating flawlessly.