Overheating when towing

[73powerstoke]

I just bought a 99 F350 SRW. It appears to be the late model 7.3. Date on engine is 12/9/98, looks like the bigger turbo and has 3" intake. I have only had it about a week, and have had no problems, other than towing today. I can go down the highway at 70-80 mph with no problems and have been since I bought it, but I hooked up a stock trailer and towed a couple horses today and it started overheating after about 20 minutes at 65-70 mph. It cools down into the normal range as long as I stay at about 55 mph. After I unhooked, I drove it and had no problems, then hooked up to flat bed trailer with a round bale of hay and same overheating problem happened again. Any ideas on what the cause might be? Thanks!

[73powerstoke]

Sorry!!! Wrong forum. But any help is much appreciated!

[Nashotah7]

hmmmm, the first ever I think I have ever heard of a overheating problem with a 7.3 I am sure there has been. Hopefully someone will come along and give some help. I am sure you have checked the obvious, coolant level, coolant age, and nothing blocking the radiator. But as for anything else I am at a loss. Have towed many miles with mine ('97) and have never had any problems. Good luck

[85_305]

+1 I've never heard of these trucks overheating when everything is running right. Check coolant level, make sure nothing floating in coolant, make sure fan is working correctly and isn't slipping etc.

[73powerstoke]

Thanks for the help! I plan on flushing the radiator and go on from there. It just seems weird that adding that little bit of weight is causing it to overheat like that.

[85_305]

It is weird and should not be happening.