Originally posted by sheltot:
Originally posted by Terry Haines:
[b]dellowm,
You KNOW why the cone is stainless and not ally as well as I do..!!!!!! Your a 'pump' guy!
Sorry about not replying over the weekend. Life is busy at times.
The method used is based on cost. Ford could have used other pump designs where the rear housing was all SS or some other material. It was just cheaper to make an insert (I assumed stamped)from SS. Given this the method of attachment should have been more foolproof.
The reason for decision to use the stainless steel material for the cone is simple and based on a number of variables. For the material it is a combination of combating corrosion and erosion and efficiency. The hot coolant in spite of the added corrosion inhibitors does have a certain amount of corrosive effect. Temperature accentuates this. Combine this with the continual high speed movement of fluid past the WP cone for all of the circulating coolant for the engine and gien the basic design it just makes sense to make this out of stainless steel (not sure what grade, 316 would be nice). The stable smooth surface would keep efficiency high (if it did not come loose).
And that brings us back again to the links to previous Terry Haines posts on the loose cone to destroyed WP relationship. The polymer open vane impeller could come loose first and in process of destroying itself cause the cone to loosen or vice versa. If either component is the cause (for any instance of failure) the WP failure will occur. From a engineering problem investigation root cause issue it would be critical to know if a loose cone or deteriorating plastic impeller were the issue. However from an 'owner' standpoint we can surmise that it can be either in any number of cases. Thus changing to a metal impeller eliminates one possibility and when doing so, the cone needs to inspected to make sure it is not loose in the slightest.
In the long term Ford should probably consider moving to a closed impeller design (as a standard for all of its cars) where a cone through its close mating relationship to the impeller vanes is not required to create the necessary compartmentalization and keep fluid transfer efficient. That does add moving mass over an open vane polymer impeller design.
