Overheating while towing
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Junior User
Joined: Jul 2013
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Overheating while towing
Alright I got a '99 7.3 Superduty F-250 I have been overheating while pulling my 1985 Camper weights around 6K.
I put a new thermostat in still overheated.
Scenario, Rpms 2500-2700 top end trying to keep fluids moving. OD to D to 2 to 1. Run in between 1 and 2 basic on the up and flat of the road.
6-8% grade engine gets hot pull over and let it cool put it in 4 wheel helps a little bit 4 wheel at least helps keep the tranny around 180. I only have a tranny gauge, I'm using the dash temp gauge for the engine.
What I'm I doing wrong or over looking.
I put a new thermostat in still overheated.
Scenario, Rpms 2500-2700 top end trying to keep fluids moving. OD to D to 2 to 1. Run in between 1 and 2 basic on the up and flat of the road.
6-8% grade engine gets hot pull over and let it cool put it in 4 wheel helps a little bit 4 wheel at least helps keep the tranny around 180. I only have a tranny gauge, I'm using the dash temp gauge for the engine.
What I'm I doing wrong or over looking.
Hotshot
Joined: Dec 2012
Posts: 11,266
Likes: 1,649
From: Las Cruces New Mexico
First is to know if it really is overheating might be a bad temp sensor.
Things that come to mind is fan clutch. Other possibilities are clogged radiator or oil cooler water pump might be bad
Things that come to mind is fan clutch. Other possibilities are clogged radiator or oil cooler water pump might be bad
It's a Van Gogh
Joined: Feb 2010
Posts: 7,795
Likes: 1,330
From: Elk Grove, CA
Further to what our freaky friend said, can you hear the fan clutch engage when it gets hot? Pretty obvious increase in fan sound when engaged. Only overheats when towing?
Pull the fan back and forth, see if the clutch is toast. Poke the serp belt to see if it is tight, bad tensioner could let it slip.
If clutch is ok most likely IMO would be blocked radiator. Over the years leaves and dead bugs build up between the fins and block air flow. Pull it out and give it a blast with water to clean the fins. Or since it is a 99 just slap in a new one, pretty sure that year did not have the oil to water transmission cooler like the later models. If you are towing you want the extra cooling for the trans.
If you end up with a new pump consider a good flush to get out all the green stuff and switch to ELC.
Pull the fan back and forth, see if the clutch is toast. Poke the serp belt to see if it is tight, bad tensioner could let it slip.
If clutch is ok most likely IMO would be blocked radiator. Over the years leaves and dead bugs build up between the fins and block air flow. Pull it out and give it a blast with water to clean the fins. Or since it is a 99 just slap in a new one, pretty sure that year did not have the oil to water transmission cooler like the later models. If you are towing you want the extra cooling for the trans.
If you end up with a new pump consider a good flush to get out all the green stuff and switch to ELC.
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Junior User
Joined: Jul 2013
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Radiator is good oil cooler is good put a 6.0 in it last fall.
New water pump last summer.
So leaves me at Bad Temp sensor? One time it overheated I lost a gallon of fluid out the cap. I think the sensor is correct. When it overheats the cap steams.
Bad fan clutch the fans spins all the time but it doesn't speed up when it gets hot.
New water pump last summer.
So leaves me at Bad Temp sensor? One time it overheated I lost a gallon of fluid out the cap. I think the sensor is correct. When it overheats the cap steams.
Bad fan clutch the fans spins all the time but it doesn't speed up when it gets hot.
Hotshot
Joined: Dec 2012
Posts: 11,266
Likes: 1,649
From: Las Cruces New Mexico
Radiator is good oil cooler is good put a 6.0 in it last fall.
New water pump last summer.
So leaves me at Bad Temp sensor? One time it overheated I lost a gallon of fluid out the cap. I think the sensor is correct. When it overheats the cap steams.
Bad fan clutch the fans spins all the time but it doesn't speed up when it gets hot.
New water pump last summer.
So leaves me at Bad Temp sensor? One time it overheated I lost a gallon of fluid out the cap. I think the sensor is correct. When it overheats the cap steams.
Bad fan clutch the fans spins all the time but it doesn't speed up when it gets hot.
the oil cooler in the side of the block not the tranny cooler
Fleet Mechanic
Joined: Nov 2005
Posts: 1,508
Likes: 87
From: North Carolina, Raleigh
have you replaced, I would call it the, radiator cap on the degas bottle.
they can go bad and not keep the system pressurized. I remember watching a bill hewitt, powerstorkehelp.com video where he highly recommended replaceing the cap as the stock cap was not strong enough spring to work properly.
they can go bad and not keep the system pressurized. I remember watching a bill hewitt, powerstorkehelp.com video where he highly recommended replaceing the cap as the stock cap was not strong enough spring to work properly.
Radiator is good oil cooler is good put a 6.0 in it last fall.
New water pump last summer.
So leaves me at Bad Temp sensor? One time it overheated I lost a gallon of fluid out the cap. I think the sensor is correct. When it overheats the cap steams.
Bad fan clutch the fans spins all the time but it doesn't speed up when it gets hot.
New water pump last summer.
So leaves me at Bad Temp sensor? One time it overheated I lost a gallon of fluid out the cap. I think the sensor is correct. When it overheats the cap steams.
Bad fan clutch the fans spins all the time but it doesn't speed up when it gets hot.
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Hotshot
Joined: Jan 2010
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From: Bristol, TN.
Fan clutch gets my vote. When it is time to go to work, the difference in sound makes it easy to tell it is engaged and on the job. 
Steve
Steve
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Laughing Gas
Joined: Jan 2007
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From: Carbondale, CO
Agree on the fan clutch.When you did the water pump, did you flush per Gooch? What coolant in there now, and level is correct?
Not sure, but i think there is a compatibility issue with the 99's and ELC.
Not sure, but i think there is a compatibility issue with the 99's and ELC.
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Junior User
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Sorry for it taking me so long to reply I didn't get any email notifications.\
The fan is not kick on it just spins at an idle speed that is it. I put a 6.0 tranny cooler in it last year cause it overheated and the tranny cooler was clogged with mud. How ever as of last year the radiator was clean.
Weird part is my fan feels solid has tension turning it by hand, doesn't have play. I was researching it and the fan clutch is good for 100,000 I have 210,000. On mine.
It only overheats when I'm pulling, and only when pulling up steep grades. I flush the system last year when I had to replace the o-ring on the bottom hose.
My bad I never did a water pump last year it was the power steering pump. Since it doesn't overheat unless under serious stress I'm going with the clutch.
Thanks for all the in put this site rocks.
The fan is not kick on it just spins at an idle speed that is it. I put a 6.0 tranny cooler in it last year cause it overheated and the tranny cooler was clogged with mud. How ever as of last year the radiator was clean.
Weird part is my fan feels solid has tension turning it by hand, doesn't have play. I was researching it and the fan clutch is good for 100,000 I have 210,000. On mine.
It only overheats when I'm pulling, and only when pulling up steep grades. I flush the system last year when I had to replace the o-ring on the bottom hose.
My bad I never did a water pump last year it was the power steering pump. Since it doesn't overheat unless under serious stress I'm going with the clutch.
Thanks for all the in put this site rocks.
Logistics Pro
Joined: Aug 2009
Posts: 3,609
Likes: 324
From: Arizona
If you mean the nut on the fan clutch it is right hand threads, so standing in front of the truck turn it counter clockwise to remove. Some Fords do have left hand threads on the fan clutch, and they are stamped on the fan shroud "Left hand threads on fan". But not the 7.3.
Cargo Master
Joined: Mar 2006
Posts: 2,502
Likes: 2
From: Bend Oregon
One other thing to consider:
Over time the internal tubes in these radiators get clogged with silicate drop out from the coolant. If enough of the radiator is clogged internally or in the right spot the fan clutch will never get hot enough to lock. The only way I have figured to diagnose it is to fill the radiator with hot water and shoot it with an IR temp gun out of the truck...just look for the cool spots. Of course by the time you have it out for me it made more sense to have the replacement on hand ($200) rather than put the original back in.
Over time the internal tubes in these radiators get clogged with silicate drop out from the coolant. If enough of the radiator is clogged internally or in the right spot the fan clutch will never get hot enough to lock. The only way I have figured to diagnose it is to fill the radiator with hot water and shoot it with an IR temp gun out of the truck...just look for the cool spots. Of course by the time you have it out for me it made more sense to have the replacement on hand ($200) rather than put the original back in.