sounds like gurgling type water sound behind my dash. can hear it pretty good when first starting the truck and can also hear it when pushing the gas pedal.seems to let up when letting off the gas pedal.dont know if this has anything to do with it,but the truck also is idled high when i first start it til it warms up,then i push gas pedal,while in park position,and it will idle down.but after driving truck when going somewhere,if i kill it,when i start it again it wont idle down,it's high idle again and i can get it to idle down.it does the idleing high randomly.sometimes i start it somewhere and it will be idled down,sometimes it's idled high,but it's getting more frequent on idling high

 

The water sound is the water flowing through the heater core. Some are louder than others, it might have air in the system that has not worked it's way out. Don't worry about it too much.

Your high idle is probably caused by a inoperative or mis-adjusted choke on the carb.

 

Nice work buddy! I second Franklin's assertion, I was coming to reference the first part when I read your title.

 

ok,thanks guys

 

I third the conclusion

 

I have a 4.9L, so am not familiar with a V8 [assuming since F250], but years ago with a 289, which had low coolant, due to a leak, the mentioned gurgling sounds could be heard. Also, the heater started blowing cold air and the temperature gauge indicated low temp. This was caused by the engine's coolant dropping below where the temperature sending unit was located. Could this be related to the original poster stating that the "fast idle" function tended to be "on" more that normal?