I took my truck out on a few 4x4 roads today, pushed it pretty hard. When I was headed home I noticed a loud hissing sound coming from under the hood. My first thought was a vacuum leak, but the strange thing is that the sound only happens when I step on the gas when the truck is in gear. It doesn't happen when I coast or idle. Also, it doesn't happen at all when the truck is in park, no matter how much gas I give it. When I first looked under the hood there was green fluid splatter all over the passenger side and on top of the air filter housing!! Blown radiator hose?? I couldn't find one. The hissing seemed to be coming from the top of the engine, and not the radiator. I'm stumped on this one, anybody have any ideas?!

It's a 1984 f250 460. Thanks!

 

Have you checked the coolant level in the truck? Make sure you are not losing coolant and its just a spray it could be coming from your heater hose as your manifold fitting is the pressure side for your heater and the water pump your suction side.

 

Thanks, I'll take a look. Which hoses should I be looking at for spraying? And what could of caused this?

 

You should look at the 1 1/2" long bypass hose between the back of the water pump and the front center of the intake manifold.
Otherwise, be looking at the heater hose that extends up through/past the smog pump bracket.

 

When in 4x4 the motor is working harder but have less air flow because of the slower speed you are moving at.
So it could have pushed out because of that. You have an over flow tank.
Dave ----

 

Ok I'll take a good look at everything tomorrow morning, thanks for the input!