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Engine overheats and makes transmission pour out fluid

i have a 96 f150 xlt 6 cyc. with auto, about 4 months ago we drove 150 miles where the engine overheated and transmission fluid started pouring out from bottom where dust cover is. when got home i filled up transmission with fluid and been good ever since with no leaks. yesterday went 70 miles and did good going down but on way back same thing, engine overheats then out comes the transmission fluid. this morning i filled it up and ran the truck and no fluid leak, any ideas on what is going on with that.

I’d take that dust cover off and see where it is really coming from. Is it coming from the filler/dipstick pipe or from a busted pipe/hose that goes between the transmission and radiator?
Since you’ve been driving it for a while without incident, it may be overheating because of you having a problem with your radiator. Are you sure your fans are coming on?

Sounds like the barrier between the coolant portion of the radiator and the transmission cooler portion of the radiator has a breech between the two. Since the tranny has a path out the fill tube, the coolant son;t pressurize and this can allow the engine to overheat and the pressure developed will blow tranny fluid out the filler tube.

You need to get this fixed. And purge the coolant system and the tranny. At this point you have coolant in the tranny and that’s surefire death.

it is a mechanical fan and i checked it, it is turning. i also checked around transmission and only sign of fluid is where it blown while driving, but on the sides of transmission it is clean of fluid.

could a bad thermostat cause the engine to overheat in turn causing the transmission to overheat and boil the fluid past the seal at the pump?

Nope.

By the way, the problem I’m suggesting will not spill fluid onto the outside of the radiator or to the sides of the transmission. The pressurized coolant will push through the breech inside the radiator and push tranny fluid up through the tranny fill tube. And yes, the engine will also overheat, because the coolant will no longer be able to pressurize. Pressurized fluid boils at a higher temperature than fluid at ambient pressure.

@the same mountainbike: Isn’t the transmission fluid at a much higher pressure than the coolant? I’d expect to find tranny fluid in the radiator, but not have the coolant push out the transmission fluid. Unless you mean maybe after the engine was shut off. Then the transmission pan would probably be full of fluid too, which would definitely be a bad thing…

I think the reason the truck is overheating needs to be addressed first. It could be a bad thermostat. A severely overheated transmission will push fluid out the vent tube. On a Ford, doesn’t this make the “O/D off” light start flashing?