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truck won't stay warm

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Old 12-28-2012, 10:41 PM
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Default truck won't stay warm

It's been pretty cold around here the last few weeks...0*F isn't uncommon. And the truck will come up to temp at highway speeds but when I slow down for a stop light or slow speed cruising through town it cools enough for the heat coming through the vents to cool.

Anyone got an idea?

Could the tstat be getting stuck open?

The fan not slowing?
Old 12-28-2012, 10:46 PM
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stuck open thermostat . not enough coolant , or maybe heater core is shot.
Old 12-28-2012, 10:47 PM
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Originally Posted by rubbinsracin
It's been pretty cold around here the last few weeks...0*F isn't uncommon. And the truck will come up to temp at highway speeds but when I slow down for a stop light or slow speed cruising through town it cools enough for the heat coming through the vents to cool.

Anyone got an idea?

Could the tstat be getting stuck open?

The fan not slowing?
termostat will get .stuck open or close , so yes
Old 12-28-2012, 11:16 PM
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Well guess ill swap it out tomorrow. Glad it stuck open and not closed. Do they only make one temp? I remember my dad used to change the stat in his old truck to a 210 in winter and a 180 in the summer.
Old 12-29-2012, 12:39 AM
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Interesting. If the thermostat was stuck open, the engine would not get to warm up completely at highway speeds. At highway speed, more cold air is travelling through your radiator, carrying away the heat of your coolant. With an open t-stat, the coolant doesn't get held in the engine block long enough to pick up heat.
If the coolant level was low, the temperature would tend to be normal travelling at highway speeds and climb rapidly whenever you came to a stop. So that's not the problem either.
A thermostat stuck closed would cause the temp to rise dramatically. Today's thermostats have a bypass hole, so stuck closed isn't likely to cause overheating. Further, they are oriented so that they are held closed by a spring pushing against the water flow. In other words, they are designed to fail open, not closed.
When the air from the vents is blowing cooler (at a stop) what is the temperature gauge showing? Does it drop, stay the same, or go up?
And yes, thermostats come in different temperatures. Just a guess, but your truck most likely uses a 185* thermostat.
Old 12-29-2012, 01:13 AM
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Originally Posted by wrvond
Interesting. If the thermostat was stuck open, the engine would not get to warm up completely at highway speeds. At highway speed, more cold air is travelling through your radiator, carrying away the heat of your coolant. With an open t-stat, the coolant doesn't get held in the engine block long enough to pick up heat.
If the coolant level was low, the temperature would tend to be normal travelling at highway speeds and climb rapidly whenever you came to a stop. So that's not the problem either.
A thermostat stuck closed would cause the temp to rise dramatically. Today's thermostats have a bypass hole, so stuck closed isn't likely to cause overheating. Further, they are oriented so that they are held closed by a spring pushing against the water flow. In other words, they are designed to fail open, not closed.
When the air from the vents is blowing cooler (at a stop) what is the temperature gauge showing? Does it drop, stay the same, or go up?
And yes, thermostats come in different temperatures. Just a guess, but your truck most likely uses a 185* thermostat.
Good information on here. One thing I would add is I would highly recommend sticking with an OEM thermostat with the original temperature range. And while you're at it you my as well flush the coolant.
Old 12-29-2012, 09:17 AM
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You raise a good point wrvond. I think I'm going to go ahead and swap out the tstat anyways since its cheap and simple...oh and the wife is away today so I won't be getting yipped at to do anything lol
Old 12-29-2012, 12:14 PM
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Also, I forgot to say that the temp is straight at half when its warm, then it drops between 1/4 and 1/2...ofcourse that is a scientific measurement
Old 12-29-2012, 06:46 PM
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Replaced the tstat...working like a charm. Nice to have heat when I don't have my foot to the floor. Thanks guys.
Old 12-30-2012, 04:49 PM
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Good stuff brother, stay warm in the winter!



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