1998 Mercury Villager • 265,000 miles

I just removed the upper & lower intake manifolds to replace the knock sensor. I completed that work, but know I have a problem putting coolant back in. I follow steps in the Haynes repair book to refill, but it always seems to push out coolant and overflow the overflow tank when heating up. I then shut the engine off, and both upper & lower radiator hoses and the bypass hose collapse. Coolant does not go back into the radiator from the overflow tank as it cools - it stays full. This happens with a U-shaped wire inserted under the radiator cap gasket as directed in the Haynes manual. I have taken off the upper intake twice before and never had this problem. It did not overheat or have coolant problems before this latest issue. Any thoughts on how to rectify?
March 27, 2013.

It sounds like you have a bad radiator cap.


Mar 27, 2013.
I already tried a new radiator cap - no change. The problem happens when I fill the radiator. I fill it up as much as possible and then start the engine, then re-install the air vent screw on top of the upper intake when it begins to flow out of the hole. Soon, coolant starts to come out of the top of the radiator, so I installed the radiator cap, but then coolant flows into the overflow tank and soon fills it. When it overflows the overflow tank, I shut the engine off. When everything cooled off, all of the hoses were collapsed and the overflow tank is still full.

Mar 27, 2013.