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Low Engine Temp

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Old Jan 9, 2019 | 11:04 AM
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Low Engine Temp

I have a 92 F150 4.9L manual tranny. The engine runs at about 150F. I replaced the whole cooling system and installed a new thermostat. I have no heat now because it's not hot enough to keep the air warm when it gets to the cab. The outside temp average is around 30-40F. The pic below is after driving the truck for 30 minutes going up and down mountains. Let me know what you guys think I can do to make the engine run hotter. Also the thermostat I put in is a 195F.

Thanks for reading this.
 
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Old Jan 9, 2019 | 11:18 AM
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Bad thermostat comes to mind. Did you use a Motorcraft thermostat? The parts store ones are known to be bad right out of the box.
 
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Old Jan 9, 2019 | 11:36 AM
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Just put a motorcraft one in today. My old one was a 60 cent one that was leaking but there was no change in temp but the truck did warm up much faster.
 
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Old Jan 9, 2019 | 12:19 PM
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Since you now have a Motorcraft thermostat installed, does it sound like the blend door is all the way to the full hot position? The cable connects to the door behind the glove box.
 
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Old Jan 9, 2019 | 01:18 PM
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The cable is rusted stuck, so I zip tied it to the full heat position and was going to swing it to AC in the summer time.
 
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Old Jan 9, 2019 | 01:42 PM
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rad fan clutch constantly engaged, or engaging too soon ?
 
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Old Jan 9, 2019 | 01:48 PM
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The heater in my ‘94 U150 (302) could cook me out of the truck. The temp gauge on that truck would sit between the N and O in normal.
 
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Old Jan 9, 2019 | 02:05 PM
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Oil pressure doesn't look so hot either
 
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Old Jan 9, 2019 | 02:47 PM
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Mine would not come up to temp because of a stuck open thermostat but since you change yours maybe a clogged heater core? Flush with hose backward and forward to clear any debris. If nothing comes out or very little it could be corroded inside. I change mine about every 10 years from leaks into the cab.

Have you changed the temp sensor. Upper right rear of the block with one wire pushed on a threaded stud. That would at least make sure the gauge is reading correctly and if the system is coming up to temp properly, the reading will be higher. Mine gauge use to read between the N&O to now between the R&M with a new sensor.

Can you place your hand on the radiator hose and leave it there for a short time? Is it HOT, hard and under pressure?
 
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Old Jan 9, 2019 | 02:49 PM
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Originally Posted by Tedster9
Oil pressure doesn't look so hot either
Bad pressure switch I'm guessing
 
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Old Jan 9, 2019 | 03:38 PM
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I have a mechanical oil pressure gauge and the stock one died but since I got a mechanical I'm not worried about a new sensor. I took a temp reader and the water pump was reading 150-155 at the water pump. The upper rad house is hot on the bottom and cold on top of the hose. I have a brand new heater core, blower fan, and resistor.
 
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Old Jan 9, 2019 | 03:42 PM
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I'm am going to get a new motorcraft thermostat just in case the one I have is bad. Third times the charm I guess.
 
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Old Jan 9, 2019 | 04:56 PM
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Originally Posted by Killer79
I have a mechanical oil pressure gauge and the stock one died but since I got a mechanical I'm not worried about a new sensor. I took a temp reader and the water pump was reading 150-155 at the water pump. The upper rad house is hot on the bottom and cold on top of the hose. I have a brand new heater core, blower fan, and resistor.
Sounds like poor circulation. You can test the thermostat by placing in hot water on the stove with a thermometer and heat it up to see when it opens and closes when it cools off.
 
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Old Jan 9, 2019 | 05:02 PM
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Originally Posted by byronbgs
Sounds like poor circulation. You can test the thermostat by placing in hot water on the stove with a thermometer and heat it up to see when it opens and closes when it cools off.
I will test the thermostat tomorrow morning.
 
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Old Jan 10, 2019 | 12:33 AM
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Originally Posted by byronbgs
Mine would not come up to temp because of a stuck open thermostat but since you change yours maybe a clogged heater core? Flush with hose backward and forward to clear any debris. If nothing comes out or very little it could be corroded inside. I change mine about every 10 years from leaks into the cab.

Have you changed the temp sensor. Upper right rear of the block with one wire pushed on a threaded stud. That would at least make sure the gauge is reading correctly and if the system is coming up to temp properly, the reading will be higher. Mine gauge use to read between the N&O to now between the R&M with a new sensor.

Can you place your hand on the radiator hose and leave it there for a short time? Is it HOT, hard and under pressure?
I have the same issue with my temp sensor. Used to be between N & O, now goes between O & R as well since being replaced. Any idea what causes it?
 
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