Low Engine Temp
FTE Chapter Leader
Joined: May 2006
Posts: 12,319
Likes: 1,298
From: Central Mississippi
Pretty sure most issues are caused by the aluminum of the manifold corroding & creating less conductivity.
Then one comes back with usually an after-market sender & too much teflon tape & the result is the same.
I pick up senders in the JY and check their resistance with increasing/decreasing heat & there's almost zero variation.
Then one comes back with usually an after-market sender & too much teflon tape & the result is the same.
I pick up senders in the JY and check their resistance with increasing/decreasing heat & there's almost zero variation.
Tuned
Joined: Jul 2002
Posts: 479
Likes: 12
From: Louisiana
They are temperature sensitive resistors. The resistance changes with temperature so the value between your old one and the new one more than likely are within a tolerance say 10 - 20% So 20% either way can cause the gauge to read higher or lower. My new one keeps the needle on the "M" most of the time with the 195 deg thermostat.
5th Wheeling
Joined: Oct 2018
Posts: 30
Likes: 0
Hi All,
I just got 87 f150 with an 302 HO and my temp sensor was bad when i got the truck and the needle was always all the way down. I went out and replaced it and now the needle sits in the same place as this. I am assuming that my thermostat was removed or bad because my heat also doesn't work but i have not dug into it yet. I know the temp sensor works and thermostat might be bad because of how gradual the temperature rises. I might dabble in checking this out this weekend and report back.
I just got 87 f150 with an 302 HO and my temp sensor was bad when i got the truck and the needle was always all the way down. I went out and replaced it and now the needle sits in the same place as this. I am assuming that my thermostat was removed or bad because my heat also doesn't work but i have not dug into it yet. I know the temp sensor works and thermostat might be bad because of how gradual the temperature rises. I might dabble in checking this out this weekend and report back.
Tuned
Joined: Dec 2005
Posts: 398
Likes: 56
From: Saskatchewan
When I first got my '88 it didn't make as much heat as I thought it should and I found the fan clutch was seized. A new clutch made things work better and made it quieter with a lot less fan noise when it is not needed. Heat is good, and necessary at 40 below.
Put your temp gun on the lines to the heater core to see what temp the coolant is going to, and coming form the heater core. Maybe there is an air lock at the heater core? If the rad hose from the water neck is only reading 150F, then coolant probably shouldn't be flowing with a 195F thermostat, should it? What is the temp of the cylinder heads? What do the spark plugs look like? Is it running so rich that it can't get up to temp? Use the temp gun to check the exhaust port at every cylinder to see if they are all firing.
Put your temp gun on the lines to the heater core to see what temp the coolant is going to, and coming form the heater core. Maybe there is an air lock at the heater core? If the rad hose from the water neck is only reading 150F, then coolant probably shouldn't be flowing with a 195F thermostat, should it? What is the temp of the cylinder heads? What do the spark plugs look like? Is it running so rich that it can't get up to temp? Use the temp gun to check the exhaust port at every cylinder to see if they are all firing.
Fleet Mechanic
Joined: Mar 2017
Posts: 1,370
Likes: 138
From: Manassas, VA
I had the same concerns though.OP: maybe try some cardboard in front of the radiator and see if it warms up any?
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Thread Starter
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Junior User
Joined: Jul 2018
Posts: 86
Likes: 0
I just put in a new motorcraft thermostat and no change in gauge or heat in the truck. Could there be an air bubble in the lines somewhere? I will try cardboard or a heavy blanket in front of the radiator and see if that helps.
Tuned
Joined: Dec 2005
Posts: 398
Likes: 56
From: Saskatchewan
Yes, there could be an air lock somewhere. Cardboard, or grille covers are not a fix for a problem in the system. Your truck should have no problem making all the heat you could want, if it is functioning properly. Blocking the air flow with cardboard is usually about getting heat quicker, not getting more heat.
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
If there's a big slug of air in the cooling system further blocking off the air flow through the radiator isn't a good idea. Let's think about this. Since it worked OK before maintenance, it seems likely an air pocket is the problem. Years ago Ford iirc had a TSB when replacing a thermostat, jam a piece of hard candy into thermostat to open it up. That way the system could be filled completely on first start and air pockets wouldn't form. Candy dissolves, works as normal, go for a beer. Might be worth a try anyway.
FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
How do you know that?
OK, what parts did that include? Did you replace the original single core rad with a double? If so that is part of the problem.
No heat in the cab may be unrelated to all this however. Are both heater core lines hot when the engine is at operating temp? If not the core may be clogged or there could be air in the system. Park the truck with the nose uphill, remove the rad cap and run the motor until the thermostat opens, if the coolant level drops you are getting air out of the system, top it up and reinstall the cap.
OK, what parts did that include? Did you replace the original single core rad with a double? If so that is part of the problem.
No heat in the cab may be unrelated to all this however. Are both heater core lines hot when the engine is at operating temp? If not the core may be clogged or there could be air in the system. Park the truck with the nose uphill, remove the rad cap and run the motor until the thermostat opens, if the coolant level drops you are getting air out of the system, top it up and reinstall the cap.
Thread Starter
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Junior User
Joined: Jul 2018
Posts: 86
Likes: 0
How do you know that?
OK, what parts did that include? Did you replace the original single core rad with a double? If so that is part of the problem.
No heat in the cab may be unrelated to all this however. Are both heater core lines hot when the engine is at operating temp? If not the core may be clogged or there could be air in the system. Park the truck with the nose uphill, remove the rad cap and run the motor until the thermostat opens, if the coolant level drops you are getting air out of the system, top it up and reinstall the cap.
OK, what parts did that include? Did you replace the original single core rad with a double? If so that is part of the problem.
No heat in the cab may be unrelated to all this however. Are both heater core lines hot when the engine is at operating temp? If not the core may be clogged or there could be air in the system. Park the truck with the nose uphill, remove the rad cap and run the motor until the thermostat opens, if the coolant level drops you are getting air out of the system, top it up and reinstall the cap.
Thread Starter
|
Junior User
Joined: Jul 2018
Posts: 86
Likes: 0
If there's a big slug of air in the cooling system further blocking off the air flow through the radiator isn't a good idea. Let's think about this. Since it worked OK before maintenance, it seems likely an air pocket is the problem. Years ago Ford iirc had a TSB when replacing a thermostat, jam a piece of hard candy into thermostat to open it up. That way the system could be filled completely on first start and air pockets wouldn't form. Candy dissolves, works as normal, go for a beer. Might be worth a try anyway.
FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
Replaced with stock single core, new water pump, thermostat & housing, new hoses, new heater core, new blower motor and resistor. I will park the truck on the hill tomorrow and bleed the system that way. Both heater core hoses are hot also. I also checked the thermostat housing with a laser thermostat from my mechanic and it was reading 150-155 after driving for 30 minutes.