Hey guys. So I've had my 65 4x4 on the road for a little over a month now. The truck does not get up to operating temperature when the truck is moving down the road and the weather is cooler than about 60-65 degrees. It usually won't get higher than 140. That is with the electric fan off also. If its warm outside than it will stay at 170-175. But I have a 180 degree hi-flo thermostat with a hi flo waterpump. It has a 445 FE(stroked 390). Aluminum intake and heads with a be cool aluminum radiator. It also has a manually operated flex a lite electric fan and shroud. I can let it idle and reach 180 but as soon as I start driving and getting air flow to the radiator the temp drops. Goes to about 140 when its cool outside, or about 170 if the outside temp is about 65+. Is the thermostat just not working properly?.
I'm thinking I should ditch the hi flo thermostat and just go with the standard, but I was told I have to use a hi flo thermostat with a hi flo waterpump.. I never would have thought not getting to normal operating temp would be a problem with a built FE! I figured it would be the opposite. Anybody have similar issues or any solutions? The weather is starting to get nasty now so the truck will be sitting in the garage for the winter but I'd like to fix this issue so its ready come spring and I can still take it out on those cool mornings.
Not getting to operating temperature.
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flareside64
- Posts: 327
- Joined: July 17, 2006, 2:19 pm
- Location: Lenox Twp, Michigan

Not getting to operating temperature.
Travis
1949 F-4 226/4 speed
1964 F100 223/3 speed
1965 F100 4x4 445/4 speed
1949 F-4 226/4 speed
1964 F100 223/3 speed
1965 F100 4x4 445/4 speed
- jkimbrel65
- Posts: 965
- Joined: July 11, 2006, 8:53 pm
- Location: Athens Al

I'd confirm the temperature with an IR gun. You may have an instrumentation problem. The 180 thermostat should begin opening at about 180 and is fully open at 200. It may be that it is stuck open and even new ones can do that. I've had that happen before, but in Texas we can't really tell until we try to drive up north. I'm not having any problem keeping my FE engine warm, but my 223 runs really cool.
1961 caribbean turquoise flareside 223
- bobenhotep
- Posts: 911
- Joined: January 9, 2007, 4:15 am
- Location: Las Cruces, NM
- Contact:

be careful shuttering a radiator if you have an automatic trans.
I d check to make sure the temp is actually what it says, then take action from there. I always ran hotter t stats than that anyway.
I d check to make sure the temp is actually what it says, then take action from there. I always ran hotter t stats than that anyway.
For every person with a spark of genius, there are a hundred with ignition trouble
My '63 short wrongbed
"The Iron Rhino"
300 I6, 3 spd manual, DS II/ HEI ignition.
Stuff I added to Hints and tricks
-300-6 choke tube repair
-duraspark II/ HEI
-Horn ring contact tube repair
-turn signal indicator fix
Mikhail Kalashnikov and Nikola Tesla are the guys i think of when i build things.

My '63 short wrongbed
"The Iron Rhino"
300 I6, 3 spd manual, DS II/ HEI ignition.
Stuff I added to Hints and tricks
-300-6 choke tube repair
-duraspark II/ HEI
-Horn ring contact tube repair
-turn signal indicator fix
Mikhail Kalashnikov and Nikola Tesla are the guys i think of when i build things.

- charliemccraney
- Posts: 1743
- Joined: July 9, 2008, 10:02 pm
- Location: Lawrenceville, GA
I guarantee it's heating up. It's not going to cool itself unless the thermostat is open and allowing coolant to pass through the radiator.
For some reason you are not getting an accurate reading. Could be the gauge. Could be the location of the sender. Are you sure you have a 180 degree thermostat installed?
Mine does the same sort of thing due to the sender location but an ir thermometer at the thermostat housing registers a temperature just above the thermostat rating.
For some reason you are not getting an accurate reading. Could be the gauge. Could be the location of the sender. Are you sure you have a 180 degree thermostat installed?
Mine does the same sort of thing due to the sender location but an ir thermometer at the thermostat housing registers a temperature just above the thermostat rating.
Lawrenceville, Ga
1961 F100 Unibody
318 Y-block (292 +.070 bore, +.170 stroke), FMS T5-Z w/Mustang 10.5" diaphragm clutch.
1961 F100 Unibody
318 Y-block (292 +.070 bore, +.170 stroke), FMS T5-Z w/Mustang 10.5" diaphragm clutch.
