As with any press fit, there are small air spaces between the oil seal and the housing, where leak paths can be created, causing corrosion. To prevent this, the space needs to be filled. You can use one of the medium strength threadlockers for the job: Loctite 243 or Loctite 248. The 248 grade might be somewhat more practical because of its semi-solid form. Simply clean the outside diameter of the oil seal with the Loctite 7063, apply the product and press into place as you normally would. Apart from the obvious leak prevention and decreased risk of contamination and corrosion, this will make the servicing of the pump easier as well, as the oil seal will be easily removed with a screwdriver.