1998 Mercury Mountaineer

Hi:
what a mess that must make. What I recommend first is to have the system serviced. They will remove all the fluid from the system and replace it with new and a conditionier. It that doesn't help, I recommend having the pump checked. It sounds like there may be a seal allowing the fluid to bleed back rather than where it needs to be. The seals wear out or get hard over the years. When the system warms, steel expands and seals soften.

Let me know if you have any other questions.

Joe