I've got a 87 F-350 with a 460 that's been rebuilt (Pretty mild, about 330 HP with just a bit over 8:1 compression.) My temp gauge is always to the right of normal and gets worse if I stop at lights, etc. I've had the system flushed by a local lube shop which taught me how to replace heater cores and I also had the thing pressure tested. . The interesting thing is that I've taken to the shop to have them replace the radiator, do whatever, and they can't get the truck to heat up..I had them throw in a new thermostat and cap. But, it seems much better when just parked. So, is it possible that the transmission could be adding to the heat problem? But when I pull away from the light where it's crept up a bit, it cools back again so that would point away from the transmission? I'm too the point where I'm going to get the radiator and everything else just replaced because I don't trust it when the temp is always that warm and fluctuates. Plus, I just had my entire A/C redone and it works great at on the road but starts to get less cool at stoplights also, I think everything would be better if I could just cool this thing down.
Thanks for any comments - sorry for the long message.

 

If your engine cools back off when you take off from a light, that means its getting more air flow through the radiator, which means your radiator is fine. The problem is that when you are stoped or going at low speeds, theres not enough air flowing through the radiator, so you need to check your fan clutch, its probly not doing its job. Or you can do what i did, put a small electric fan in front of your radiator to help when the a/c is on.

 

I'm wondering if you have a sending unit in that engine that should be for a warning light instead of a gauge,thatis of course if the needle is outside of the normal band.

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Thanks for the replies. I forgot to mention that I put on a flex fan so the clutch should be no problem plus I did replace the sending unit (from Ford) and I'm pretty sure it's the right one. It's not past the right normal line, just too far to the right for me. I think the radiator is a 2 row, do you think a wider one can be fitted in?

 

I had a similar problem, with the truck sitting at about halfway, a little over, and it would overheat every now and then.. but I think our problems were a little different.. I have a 302 and the radiator was a SINGLE CORE radiator.. with a crack in it.. I dont know where the hell that thing came from.. so I replaced it with a dual core.. my truck is an '85.. with these model trucks, you CAN get a 4 core super heavy duty radiator, but it seems like your problem is with airflow. When you are stopped, it gets hot and the AC doesnt work well, but when you accelerate it does? Well that shows that you aren't pulling enough air through when you are stopped. The AC cooling back up when you start accelerating reinforces this. Might be that the flex fan you put on doesn't pull enough air? A buddy of mine put one on that was too small.. had similar problems. Is your fan shroud still in place? Maybe a fan clutch? For alot cheaper than a radiator you can slap an electric fan on there I'm sure would help.. I wouldn't buy a new radiator yet if I were you.. Good luck!