I have a hunch that my radiator is partially plugged. Did a lot of searching, couldn't find much on radiators being plugged. System was flushed 6-months ago with Restore/Restore+ and is running ELC coolant. I flushed the radiator by itself a few times and got some large "slivers" of dirt coming out. Flushed until it didn't seem to have any more coming out. New oil cooler, don't appear to have any oil temp issues.

Truck is a 2005 F250 6.0. 105k miles, all stock. Had truck for about 6-months. First time towing with it. Temp indicated by Scangauge. When cold the ECT/EOT are within 1-2 deg of each other so I think they are accurate.

Thermostat is a 6-month old Ford unit.

While unloaded on the flat-lands ECT runs around 190-195. Will peak up to 200-205 after a hard acceleration, but quickly come back down. Oil temps typically 8-10F off the coolant.

Starting going to the mountains with no trailer and was surprised to see the ECT jump up to around 210 as soon as I start climbing. Decent grades, around 4-6%. Outside temperature around 70-80. ECT would rise up to 210, fan would come on to a mid-speed (~1000rpm) and temp would hold around 205-210. Not alarming, but higher than I would expect, especially unloaded. Oil temp again staying within 10F of the coolant.


Odd part is there seems to be no middle ground, as soon as I'd hit the flats again, the coolant drops down to 190 and holds there. Truck either runs at 190 or 210.

Hooked up medium-sized toy hauler, around 6500 fully loaded. On the flat-lands with stop-signs every mile I'm holding around 205-210. Oil temps around 10F above ECT.

Then I climb a 8-mile 6% grade (Highway 168 in the Sierras), holding the truck at 50mph, running around 22-24psi boost and about 3/4 throttle. ECT rises up to 225 before the fan kicks in at full speed (3000rpm and LOUD). With fan running temp drops to 220 and holds. Fans runs full speed all the way up, wife & kids are complaining. Outside around 95F, air conditioning on full-blast. Once at the top of the hill it cools off. EOT pretty much following the coolant, just +15F once I hit the hill. Pretty much held at 235.

Seems like I'm just not getting the performance out of the radiator? I'm a little worried about pulling larger loads up this hill in the future. From Bismic's post about typical temperatures, anything over 215 on the ECT is "alarm"? Seems like a lot of others are getting lower temps pulling larger loads?

For reference, my old 2002 F150 with 260hp 5.4 did the same hill, same trailer only at 30mph and it held 215F ECT the whole way up. The radiator in that truck had been rodded & resealed.

 

Did you use tow/haul mode or pull it down a gear? Might not be the radiator, could be water pump.

 

Yes, was in tow/haul. Engine RPMs were around 2,700 if I recall.

 

have you inspected the fines of all cooling units up front for sufficient airflow? bent fins and bugs can clog em up.

in my experience a clogged radiator will have cold spots one can feel by (carefully) feeling it after the system is warmed up and SHUT DOWN. it should be evenly warm.

it may be difficult to access, and may even merit a removal of fan shroud, short test drive, then see how it is.

 

use a digital thermometer instead of your hand, its less subjective.

 

A radiator does not have to be completely plugged simply restrict the flow of coolant enough or the flow off air enough to affect the heat exchane efficency of the radiator to cause problems. Not only folded over fins will affect air flow but oxydation build up on the fins will reduce their heat exchange efficency.
When you look at a new radiator out of the box the metal is kind of shiny but within a few monts of exposure to the elements it will dull. That is oxydation it acts as a barrier or blanket and cuts it's heate transfer rate.

 

I finally got this issue resolved. It was the radiator. I pulled the stock radiator and it was filthy. Tried cleaning it with a normal hose nozzle, too afraid to use a pressure washer. Got the outside clean, but I could see that there was still a lot of block inside the fins. Made a small difference in temps, but still ran up hot.

So I decided to buy a new radiator. Ended up just going with a stock replacement from Ford.

I tried the same grade at around 65-70mph unloaded and I couldn't get it above 195! It used to get up to almost 210-215 on that same grade unloaded.

Did another long grade (152 over Pacheco Pass), about 3-miles 6-7% at 70mph in 40F ambient temps and the dang thing didn't even budge from 190!

Will try it with the trailer soon and report back.

 

Glad you got it fixed!

Something similar happened to me and I wasn't towing anything. My radiator was cracking and my truck would spike to 220 ect just cruising unloaded in the summer heat. It wasn't until the end of July, it finally gave and I replaced it with a Mishimoto Aluminum radiator. $380 shipped to my door off amazon.