ok let me re-do this. ive spent a lot of time trying to diagnose this problem, here's the deal: (04 5.4 Expy) I can crank the truck up in the morning, everything is fine, A/c blows cold. I can go on a 10-15 minute drive and turn the truck off. It sits for say 20-30 minutes. Crank it back up, temp gauge pegs at H and slowly begins to decrease. During this time, the A/C will not cycle on (im assuming a safety precaution?) until the temp gauge gets back down to normal range (in the middle of the gauge). When it finally comes down, a/c kicks in and all is well. whats up with this? Coolant level is good and clean (no oil), upper radiator pipe gets hot, does not get hard, no leaks, heat seems to work (it is hot in georgia right now though) no coolant in oil. maybe temp sensor???? im stumped.

 

ttt

filler

 

wow, that looks rough. What's the question again? Pressure test for sure!

 

up up up, changed my initial post

 

hard to say, I would start with a thermostat and radiator cap, flush the radiator and refill with 50/50 mix of antifreeze and distilled water or you can purchase the 50/50 mix at an auto parts store. If it still gives you problems, feel the upper and lower radiator hoses. If one is hot and the other cold, then you might have a partially clogged radiator.

It could be anything in the cooling system that is causing this. Sometimes, these are harder than electrical problems to sort out. Let us know how it turns out!

Good Luck!

 

Actually the problem nay not be a problem at all. When you stop and turn off the engine the temp in the engine will always rise for a while before it starts to cool from sitting and if the A/C dosen't come on right away it's because of the ECM responding to the info it gets from all of the sensors. As soon as the ECM believes that alls well it allows the A/C to function.

 

For what it's worth, mine has never pegged at Hot. Never. I do have a question though. Is the vehicle stationary while the gauge is pegged and stationary when it cools back down or are you driving when the vehicle begins to get back to normal range?

I guess you could have air in the system too.

 

well guys, thanks for the help, i fixed it. expecting the worst i bought a new intake, gaskets, thermostat, temp sender and new coolant. started the disassembly process and found my problem as soon as i pulled the thermostat housing. the thinnest part of the plastic that's supposed to hold the o-ring for the crossover pipe had broken and the ring was kinda hangin out a bit inside under the thermostat! the broken pieces were stuck in the hole where the water would go thru, they werent big enough to stop it up though. i couldnt see it but it had been leaking for a while, the sensor was CAKED with white crust and it had been running down into the valley! cleaned everything up, replaced the intake, installed the new stuff and all is well. i finished friday afternoon and we've driven it since then, all seems well!!


you know, i love this truck, it drives so nice and we've never had a problem with it in the last 4 years of ownership. but i really hafta ask... PLASTIC intakes? wtf? i work for my city and most of the crown vic police cars (interceptors w/ 5.4s) have come in for intake problems of some kind. im a die hard ford fan but dang! who decided on this design? oh well, it's a labor of love.