Running Hot but only after a while?
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Senior User
Joined: Aug 2010
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From: Agawam MA
Running Hot but only after a while?
Hello all,
New issue here, took the truck on a 20 mile trip to work and back. Both ways, the truck's temp moved up as would be expected as it warmed up. Went to the "N" on normal, then stopped there, which I assume is the Thermostat opening. Stayed at the "N" for 5 miles. Now after 10 miles into the trip, starts to creep up every time I applied ANY throttle, and creeped up a bunch on hills... made it the final 10 miles, went from the "N" to the "L" during the last 10 miles. When I stopped the truck felt very hot, not quite boiling over, but the overflow tank was quite a bit more full.
So, why would the motor warm up for 5 miles, stay the same for 5 miles, then slowly start to overheat?
Thermostat is the correct Ford model, and I know I need a real temp guage but I thought this was strange and someone might have an idea...
Thanks!!!
New issue here, took the truck on a 20 mile trip to work and back. Both ways, the truck's temp moved up as would be expected as it warmed up. Went to the "N" on normal, then stopped there, which I assume is the Thermostat opening. Stayed at the "N" for 5 miles. Now after 10 miles into the trip, starts to creep up every time I applied ANY throttle, and creeped up a bunch on hills... made it the final 10 miles, went from the "N" to the "L" during the last 10 miles. When I stopped the truck felt very hot, not quite boiling over, but the overflow tank was quite a bit more full.
So, why would the motor warm up for 5 miles, stay the same for 5 miles, then slowly start to overheat?
Thermostat is the correct Ford model, and I know I need a real temp guage but I thought this was strange and someone might have an idea...
Thanks!!!
Thread Starter
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Senior User
Joined: Aug 2010
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From: Agawam MA
Coolant is clean and brand new because I just drained it to do the head gaskets... PO had Blue Devil head gasket sealer in it to try to fix the leak, so this looks like a poorly flowing radiator?
Postmaster
Joined: Jan 2010
Posts: 4,319
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From: Elk City, OK
it could be the radiator fan clutch like gnathv said. get it warm, just right before it overheats...... then shut it down, hop out real quick and try to turn the fan by hand. if it still spins freely then its the clutch. if its locked up or damn near locked up then your good.
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From: Agawam MA
So would the truck hold a good temp for 10 miles then slowly get hotter if the radiator was clogged? When I got home I left it idle and the temp slowly came down from the "L" to the "M" before I shut it down.
Cargo Master
Joined: Mar 2010
Posts: 2,227
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From: Higginsville, MO
mine did the same thing but it was the gauge..... got my mechanical in and she sits between 185-195 down the highway at 80-90 degrees outside
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From: Des Moines
Are you sure it is the right radiator? These old IDI's had a HUGE radiator in them. If the PO grabbed just any old radiator from an F250, he might have grabbed a gasser radiator. It would keep it running for awhile, until it got clogged up, even minorly, and them you are gonna have overheating issues. You sure wouldn't have enough cooling capacity to tow anything, and even running at 65 mph.
Are you blowing bubbles out of the radiator, indicating a head gasket leak or cavitation blowing air into your coolant? Any coolant into the oil? Either one would be indications, along with overheating, that you have serious problems. As it is, either you have a radiator or a water pump issue.
Are you blowing bubbles out of the radiator, indicating a head gasket leak or cavitation blowing air into your coolant? Any coolant into the oil? Either one would be indications, along with overheating, that you have serious problems. As it is, either you have a radiator or a water pump issue.
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Cargo Master
Joined: Mar 2010
Posts: 2,227
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From: Higginsville, MO
Thread Starter
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Senior User
Joined: Aug 2010
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From: Agawam MA
Yep, it is a 7.3 idi radiator, but it definitely has seen better days...
Ordered a lifetime guarantee new one from Autozone, $305 shipped to my door...
Thanks for the confirmation of what I feared, all I can say is this truck should run really well since I have replaced almost everything now!
Ordered a lifetime guarantee new one from Autozone, $305 shipped to my door...
Thanks for the confirmation of what I feared, all I can say is this truck should run really well since I have replaced almost everything now!
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Joined: Mar 2010
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Your problem
I had the same exact problem. Not sure if you figured it out by now but I can ALMOST bet you it is your water pump once again. The POS water pump impellors (plastic) suck on this things. Mine impellor was cracked just enough that it would run perfect temps when idling or not in the throttle.
However if you got into a higher rev. like 2k then the truck would immediately start running hot, when you let off the truck went back to normal. Sorry for the spelling I'm not a english teacher or anything, just trying to help out my fellow ford 6.0 diesel guys/gals.
However if you got into a higher rev. like 2k then the truck would immediately start running hot, when you let off the truck went back to normal. Sorry for the spelling I'm not a english teacher or anything, just trying to help out my fellow ford 6.0 diesel guys/gals.
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Joined: Oct 2010
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I just fixed a similar problem. Ran some Prestone flush through it a couple of times and it helped quite a bit, cleaned a lot of crud out of the radiator. Fan clutch fixed it for good since temp still climbed during stop and go driving, highway and idling ran cool with the clean radiator.
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Senior User
Joined: Aug 2010
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From: Agawam MA
Driving the truck, the factory sucky gauge comes up quickly to the N on Normal and stays there all day long, hot, cold, A/C or heat on, hills or flats... So for the record, this one is in the books... 
Postmaster
Joined: Apr 2009
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From: Malahat/Cowichan Valley
I had the same exact problem. Not sure if you figured it out by now but I can ALMOST bet you it is your water pump once again. The POS water pump impellors (plastic) suck on this things. Mine impellor was cracked just enough that it would run perfect temps when idling or not in the throttle.
However if you got into a higher rev. like 2k then the truck would immediately start running hot, when you let off the truck went back to normal. Sorry for the spelling I'm not a english teacher or anything, just trying to help out my fellow ford 6.0 diesel guys/gals.
However if you got into a higher rev. like 2k then the truck would immediately start running hot, when you let off the truck went back to normal. Sorry for the spelling I'm not a english teacher or anything, just trying to help out my fellow ford 6.0 diesel guys/gals.