I asked my Ford dealer what year radiator will interchange with my 1985 F150 (carbureted 302, AOD) and was told all 302 engines from 1985 - 1996 with single core radiator were the same. I found a good replacement radiator from the junkyard from a 1994 F150 and it fits perfectly except the 1994 radiator has an extra open port below the radiator overflow tube, right above where the radiator automatic transmission cooler is located.

This radiator came with a metal crossover tube of some sort that connects to this open port and crosses over the top of the radiator and to the other side where the upper radiator hose is. A 3/8" coolant hose is attached to this tube and faces toward the engine.

Does this tee into to the heater hose return line for some sort of automatic transmission fluid pre-heater?

 

on my 94 with a 5 speed that tube is just capped off, i was wondering what it was for yesterday

 

The extra port is used on EFI engines. It goes to the throttle body and supplies it with warm water. Just plug it for your engine.

 

So the warm water (coolant) flows from the intake manifold, through the throttle body, and then to the radiator through that metal crossover tube?

Is that the only reason for this part?

Why would Ford go through all that trouble to use a metal crossover tube to route the throttle body heater all the way around to the other side of the radiator, where the automatic transmission cooler is located?

 

The pressure differential is larger from the throttle body to the tank on the cold side of the radiator than it is to the tank on the hot side. It was probably routed that way to help bleed air out of the system since the throttle body is close to the highest point in the system. Although, I'm not sure why they changed from the setup used on my '87, with the throttle body feed and return on the feed and return of the heater core.

 

So this extra port on the "cold side of the radiator" has nothing to do with the automatic transmission fluid cooler located in the radiator?

 

No, it does not have anything to do with the trans cooler.

 

I suppose I could just cap it off, but I am bored, and this crossover tube seems rather interesting to me for some reason...

Well, when the engine is cold, and the thermostat isn't open yet, wouldn't both sides of the radiator be "cold?" My guess is the purpose of the throttle body heater is to warm it up faster at start-up on a cold engine for better driveability? There would be no coolant flow through either side of the radiator on a cold engine at start-up (or before the thermostat opens), which means that there must be another reason why Ford decided to spend the extra money to supply a long metal tube with crimped rubber ends to bypass the water pump and route the coolant all the way across the radiator.

Wouldn't the automatic transmission fluid also benefit being warmed up as soon as possible on a cold engine the same way it would benefit the throttle body? It just seems logical to me that Ford would have decided to route the same hot coolant used to heat up the throttle body to also heat up the automatic transmission fluid in the radiator.

Doing some research, it seems that Ford originally had the throttle body heater teed into the return line of the heater hose. A simple hose tee would have been much cheaper to produce than a long metal tube with two crimped-on rubber ends. For some reason, Ford felt it was necessary to bypass the water pump and use this tube to route the coolant all the way over to the far side of the radiator, right above where the automatic transmission cooler is.

Your 1987 model would have used the AOD. The E4OD and AODE were introduced a few years later, which are both computer-controlled automatic transmissions. I wonder if that had anything to do with adding that radiator crossover tube and routing the coolant directly over the transmission cooler?

 

I have that extra nipple on my radiator too, and a metal tube connects there and connects to the throttle body. I have an E4OD automatic transmission, so you may be right on the pre-heat idea. I always wondered what that was for.

 

The original Rad in my 89 F150, C6 doesn't have that, and the fill hole for the rad is on a 45* angle towards to the engine.


I need to replace it as it cracked and leaks when pressure builds on the drivers side top. Silly plastic.....



My parts truck Rad, 300 EFI 5 speed has a straight up filler cap and that little extra port right under the rad cap. It's plugged off.

 

yea dealers wrong there were a few changes like the fill neck and that port could be for alot of options if its not applical to your just plug it and go on

 

You are right that there is not any flow through the radiator with the thermostat closed, but the throttle body coolant line would essentially bypass the thermostat since it is connected between the water pump outlet and the water pump inlet (i.e. "cold" side of the radiator) even with the thermostat closed. The air bleeding idea is all I have as to why Ford used the long metal tube.

Maybe this was part of their reasoning as well.

It could be, but I have a manual. I haven't worked on a lot of these trucks, but the only one I saw that had the metal crossover tube from the throttle body was the '94 or '95 truck I got a spare engine from. It was an automatic, E4OD if that makes any difference. My dad's 92 is a six cylinder and I don't think it has a long tube from the throttle to the radiator. Still, the biggest reason for the tube that I can see is improved ability to bleed air out of the system. The long tube would force air bubbles to the side of the radiator with the filler neck rather than continually recirculating the air bubbles between the throttle, heater core, water pump and block. That's my best guess...