I have a 99 Ford Contour with a four cyl. The top radiator hose keeps coming off when there is alot of pressure on it.What could possibly be wrong with it?

Pressure is regulated by the pressure cap. This is on the recovery tank in this car I think or if not on the radiator itself. The average system won't exceed 15lbs or will blow off the pressure or normally just send coolant to the recovery tank and draw it back later as it cools down and looses pressure.

This hose somehow is just not attached or tighned properly. It's rare that a system can exceed the pre-set pressure but never allow that as the weak link could be a nasty problem like the heater core or radiator! Cooling systems all will blow steam or coolant out to the ground if overwhelmed with pressure like when boiling over in an overheat situation. That vent must be open and could be just a plastic spout or tube.

Get a good new clamp for that hose if in question. Carefully fill up the system and purge out all air and check that it is operating properly.

For now it's just a hose clamp/fastening problem but verify that it can't exceed the pressure for the car,

T
Tom Greenleaf - MetroWest Boston - USA
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http://www.autoacsystems.com/tomgreenleaf/

Thanks Tom for theinfo!If that doesn't work I will let you know.