What would cause a power steering pump to go out repeatedly on a 1999 Ford F-250 diesel?

Answer 1

I would say most likely HEAT! Does the Power Steering unit have a cooler? When you changed the power steering unit previously did you replace, not replenish, replace the fluid? Usually pwer steering pumps run a long time but once the fluid gets contaminated, either with dirt, debris or the lubricants are cooked out of the fluid then the fluid doesn't keep the seals soft. When the seals get hard the unit leaks and sometimes whines and squeals. I have added Lucas Power Steering Additive to some power steering untis that were on thei rlast legs to get them to last awhile longer. It's about $10.00 for a small bottle but it did stop leaks. If your power steering unti is out and you are going to replace it, look into adding a cooler to it, a small condensor that will remove some of the heat from the fluid. Or you could maybe insulate the power steering unit with some sort of insulation material. The power steering unti sometime sits very close to the headers or exhaust manifolds which helps deteriorate the fluid. Power Steering fluid is one of the most overlooked fluids. Many of today scars use Transmission Fluid for the power steering fluid and if you ever have a transmission get the fluid all hot, you will soon be replacing or repairing the tranny.