to answer the air flow direction question, the flow is towards the motor, fan will pull cool air from the outside suck threw the radiator to cool the fluid, and blow hot air off the motor. do you boil out after you shut the motor down, if so you will get run out, if you use a resevior of some type to catch the extra run out the motor will suck it back up when it needs it the next time you run it. you want to make sure your overflow hose goes to the bottom of the resivor.

 

Use a 15 or 16 lb. radiator cap. I prefer the "Stant lever vent". Dont wory about the radiator being to weak, (keep in mind that a carbonated soft drink in a glass or plastic bottle is under more pressure than that.) Also, don't bother messing with the heater. It has no bearing on the cooling system what so ever.

If the new cap doesn't fix your problem, take the truck to the radiator shop and have them test it for CO (carbon monoxide) in the coolant. a blown head gasket or cracked casting could allow exhaust gas into the cooling system which will allways cause over heating. If the system is OK, have them look at your fan, fan clutch, fan shroud, ignition timing, and bottom radiator hose. (some replacements don't have the "spring" inside them and will start to collapse over time.) They can also check for water flow! One of these items is the problem! (you already replaced the thermostat). Finding it is just a simple process of elimination.

 

you should be able to see a wire attached to what looks like a 3/4" bolt just to the left of the water pump next to the timing cover.

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77'FORD F150 XLT 400

 

Thanks for the advice all. Ran the truck last night quite a bit and had no problems whatsoever. Think tightening the hose all the way allowed for the pressure in the system to stay. Also tightening the fan belt a bit more too. Going to leave it for now and see how it goes when we get a hot day again here in CT.

By the way, anyone have a golden rule that goes something like this, "don't attempt to fix even the smallest problem before work, no matter what time you get up in the morning"? I grabbed a new sending unit for the temp guage last night, and after some looking around (found the oil pressure unit first) found the old sending unit. Took it out, then went to put the new one in. Should've been easy, but the damn thing wouldn't go in. A bit cumbersome to get at, but after taking a few hoses off and trying to hand thread it in, just wasnt going. Figured it might be the size, but when I tried the old one that wouldn't go in either. After about 1 1/2 hrs, I gave up and chaulked it up to the engine being a little to hot and the metal a lit expanded. (yeah the engine was hot, I didnt realize fluid would come pouring out when I took off the old one). Anyway, my roommate's going to try in a while, and if he doesnt get it, I'll try later. I left with him saying, "oh, that's it? Piece of cake. I'll have that in in no time..." Just in case I'm missing something though, anyone else have this problem?

I looked through a couple of old threads and found the answer to the fan direction thing. At someone's advice I put a piece of paper to the radiator with the engine on and it stuck like glue. I have a shroud, so I think that helps a little at least. I dont have a fan clutch, or electic fan. Just the stock belt attached to the power steering resevoir as well. Anyway, thanks again for the replies.