overheating issues
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Mountain Pass
Joined: Sep 2004
Posts: 146
Likes: 2
overheating issues
91 f350 dually with 93 7.3 automatic. transmission plumbed thru radiator and 12" x 12" aux. tranny cooler. only overheats pulling 5th wheel up 6% grades approx 18000 to 20000 lbs combined. my first thought was the fan clutch since i have never heard it lock up since i bought the truck. put on a new fan clutch same thing so i took it back and got a replacement thinking it was defective. now the 3rd clutch this month is not locking up either. i have good flow through the radiator fins. the tubes inside have very little if any calcium buildup. as of right now i only have the factory temp gauge, which as soon as it hits the l it immediatley pegs out along with my other gauges. when this happens it is bubbling into the overflow and contained there.cools back to normal within 2 to 3 minutes engine running and i am off again. no collapsed hoses, no bubbles in the radiator. egt's 950 to 1000 post turbo pulling grade. 35 mph. 2 mile long grade.
question is what next? what will make it overheat without the fan clutch kicking in? thermostat? radiator cap?
question is what next? what will make it overheat without the fan clutch kicking in? thermostat? radiator cap?
Cargo Master
Joined: Mar 2010
Posts: 2,227
Likes: 149
From: Higginsville, MO
thermostat or radiator cap would be 2 good things to replace as they are cheap..... work truck which is a gasser started overheating and boiling back into the overflow and all we had to do was change the radiator cap and she was fine..... mine will be getting a cooling system overhaul this fall before winter.... new thermostat, radiator cap, some lines, flush, some john deere antifreeze.....
Methanoholic
Joined: Mar 2009
Posts: 6,442
Likes: 8
From: Maine (NorCal Native)
You should definitely hear the fan when it locks up. it'll sound like a tornado!
Get a REAL temp gauge ... Whats "l" mean in temp????
There is nothing that'll affect the fan hub engagement except lack of HOT air hitting the fan hub... If you look on the front of the hub there is a coil spring looking thing, that expands when hot air from the radiator hits it engaging the hub.
Clutch Fan Hub Test
Ensure air flow is getting through radiator, Do you have A/C, is the condenser plugged preventing airflow through the radiator, is there garbage between the condenser and radiator.
If you do replace the thermostat use Motorcraft E5TZ-8575-C or Navistar 1807974C94 thermostat only and ensure the check ball moves freely.
Use a 13lb radiator cap.
-Enjoy
fh : )_~
Get a REAL temp gauge ... Whats "l" mean in temp????
There is nothing that'll affect the fan hub engagement except lack of HOT air hitting the fan hub... If you look on the front of the hub there is a coil spring looking thing, that expands when hot air from the radiator hits it engaging the hub.
Clutch Fan Hub Test
Ensure air flow is getting through radiator, Do you have A/C, is the condenser plugged preventing airflow through the radiator, is there garbage between the condenser and radiator.
If you do replace the thermostat use Motorcraft E5TZ-8575-C or Navistar 1807974C94 thermostat only and ensure the check ball moves freely.
Use a 13lb radiator cap.
-Enjoy
fh : )_~
Thread Starter
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Mountain Pass
Joined: Sep 2004
Posts: 146
Likes: 2
right now i am thinking thermostat not opening up all the way. hot coolant in the engine being restricted to the radiator, allowing the radiator to remain cool enough not to engage the fan clutch. will have to get a thermostat this weekend and try it. the truck does have a/c and the condensor is clear with no bent fins. a real temp gauge is on my to do list along with trans temp gauge which i have.
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