351M Runs Cold
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New User
Joined: Jun 2012
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351M Runs Cold
1978 F250
192F Thermostat
No Shroud
6 Blade Flex Fan
90% Of Radiator Covered
3 Core Radiator
This 351M still runs at 180F tops. Dash gauge stays on C. Getting ready to put on a 4 blade fan to see if that helps. Cold is fine for summer but not winter. Anyone know why it would run this cold all the time?
192F Thermostat
No Shroud
6 Blade Flex Fan
90% Of Radiator Covered
3 Core Radiator
This 351M still runs at 180F tops. Dash gauge stays on C. Getting ready to put on a 4 blade fan to see if that helps. Cold is fine for summer but not winter. Anyone know why it would run this cold all the time?
Senior User
Joined: Oct 2012
Posts: 197
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From: Dublin CA
Im confused at what your are saying. The engine runs at 180 but the temp gauge stays on C ? You have a guage/wiring/sending unit/ issue. Check the flow of your heater core. Throw a garden hose on it and see that water flows well out the other side. Honestly, 180 engine temp is more than enough to heat up a functioning heater core. Did you measure engine temp at the upper hose neck coming off the engine with an infrared thermometer?
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New User
Joined: Jun 2012
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Im confused at what your are saying. The engine runs at 180 but the temp gauge stays on C ? You have a guage/wiring/sending unit/ issue. Check the flow of your heater core. Throw a garden hose on it and see that water flows well out the other side. Honestly, 180 engine temp is more than enough to heat up a functioning heater core. Did you measure engine temp at the upper hose neck coming off the engine with an infrared thermometer?
Fleet Mechanic
Joined: Jan 2012
Posts: 1,668
Likes: 13
From: Saskatchewan
If you have a 192f thermostat it should run at least 192. The thermostat controls your minimum engine tempeture. So you have a bad thermostat or a bad gauge. If you have already changed the thermostat I would lean towards your aftermarket gauge, I would go pick up a inferred tempeture gun and shoot your thermostat housing after you have it warmed up real good. And 180 is a nice temp to run at anyway. Also the heaters 30 years ago weren't quite as good as now days, as well as cab insulation. Hope this helps.
Mountain Pass
Joined: Jun 2006
Posts: 239
Likes: 10
Six steps to warm toes
"heater's not as good" means they were smaller and didn't have as many heat exchange fins. But they worked just fine in the day. Here's what you need to look at:
1) put in a hotter rating thermostat
2) thoroughly flush the heater core. These old cores can accumulate a lot of crud. To be extra sure, pull it and take it to a radiator shop to be boiled out. You'll be amazed at all the crap that comes out of an old core.
3) Make sure your fresh air vents are closed and sealed nicely. Doh!
4) Door and window seals leaky? guess what? you just overwhelmed the heater. Replace them. Sliding rear windows with poor seals suck a lot of heat and AC out. Double check those.
5) Guess what effect rust holes in the floor have? Patch them if you have them.
6) Finally, if you need too, hang an auxilliary heater under the dash. Just pipe warm water to it, hook up a wire to the motor and feel your feet get happy.
Good luck!
1) put in a hotter rating thermostat
2) thoroughly flush the heater core. These old cores can accumulate a lot of crud. To be extra sure, pull it and take it to a radiator shop to be boiled out. You'll be amazed at all the crap that comes out of an old core.
3) Make sure your fresh air vents are closed and sealed nicely. Doh!
4) Door and window seals leaky? guess what? you just overwhelmed the heater. Replace them. Sliding rear windows with poor seals suck a lot of heat and AC out. Double check those.
5) Guess what effect rust holes in the floor have? Patch them if you have them.
6) Finally, if you need too, hang an auxilliary heater under the dash. Just pipe warm water to it, hook up a wire to the motor and feel your feet get happy.
Good luck!
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Hotshot
Joined: Feb 2004
Posts: 10,788
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From: The Shenandoah Valley
As you look further and further back in old car adverts you'll see more and more heavy clothing being worn by the models or figures (if a painting) in the winter scenes.
Back in the old days, people dressed for a long walk home. It's still a good idea.
My '77's heater and AC never heated or cooled like my '07's does, it also does not have heated leather seats. I think you could stay roaste toasty even butt naked in the '07 once warmed up .... but on a cold day .... not the '77 ....
Back in the old days, people dressed for a long walk home. It's still a good idea.
My '77's heater and AC never heated or cooled like my '07's does, it also does not have heated leather seats. I think you could stay roaste toasty even butt naked in the '07 once warmed up .... but on a cold day .... not the '77 ....
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New User
Joined: Jun 2012
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Fresh air vents are closed but door seals and window seals are bad. Have a new set planned to go on after paint in the spring. The floor is "new" with no holes. The thermostats is from parts store. Where do I get a correct one?
Senior User
Joined: Oct 2012
Posts: 197
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From: Dublin CA
can you elaborate? we arent dealing with obd 2 engine management. a gates t-stat should be fine imo.
Fleet Mechanic
Joined: Jan 2012
Posts: 1,668
Likes: 13
From: Saskatchewan
The 335 series engines use a special thermostat with a little collar (for lack of a better term) on the bottom of it that blocks off a internal bypass in the block when the thermostat is open.
Post Fiend
Joined: Mar 2011
Posts: 8,501
Likes: 4
From: Lynchburg, VA
The 335 engine series uses a different cooling system design that requires the thermostat to block off a by-pass when the engine reaches operating temperature.
Yeah, and parts stores don't do application specific for parts like thermostats.