Heating problem
Fleet Mechanic
Joined: Oct 2004
Posts: 1,395
Likes: 105
From: Southern KS
You should have one on passenger side up high in the engine compartment with a vacuum hose going to it. It is inline to the coolant hose going to the heater core. I believe if someone has removed this you would have heat all the time even if A/C is turned on.
It could cause the problems you are having either by inconsistent vacuum or a dirty sludged up valve that can't open fully.
It could cause the problems you are having either by inconsistent vacuum or a dirty sludged up valve that can't open fully.
Fleet Mechanic
Joined: Feb 2007
Posts: 1,652
Likes: 79
From: Mooresville, NC
Likelihoods (probabilities of problem source):
Low engine coolant -- low
Engine overheating (assuming your temp gauge, sensor (you have two in 5.4Ls -- one on the head that feeds the PCM and one on the intake that feeds the dash) and thermostat are functioning "ok" -- you can "instrument" with free OBD2 tools see the head sensor values) - low to zero probability
Plugged or partially plugged heater core -- low to mid
Temp blend door sticking / binding -- mid to high
A/C blend door actuation - mid to high
Incorrect heater valve operation -- mid to high --- use a hand held IR Temp Gun (I use my Fluke daily as a general purpose (almost everything on vehicles) troubleshooting tool) to verify temps in/out of valve
Low engine coolant -- low
Engine overheating (assuming your temp gauge, sensor (you have two in 5.4Ls -- one on the head that feeds the PCM and one on the intake that feeds the dash) and thermostat are functioning "ok" -- you can "instrument" with free OBD2 tools see the head sensor values) - low to zero probability
Plugged or partially plugged heater core -- low to mid
Temp blend door sticking / binding -- mid to high
A/C blend door actuation - mid to high
Incorrect heater valve operation -- mid to high --- use a hand held IR Temp Gun (I use my Fluke daily as a general purpose (almost everything on vehicles) troubleshooting tool) to verify temps in/out of valve
Thread Starter
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New User
Joined: Nov 2020
Posts: 14
Likes: 0
Hi guys
I went out this morning and looked for the vacuum hose for the heater control valve. I did not find one. I owned this truck since November 2019 and never seen the heater control valve.
I did put a piece of cardboard in front of the radiator.
I went out this morning and looked for the vacuum hose for the heater control valve. I did not find one. I owned this truck since November 2019 and never seen the heater control valve.
I did put a piece of cardboard in front of the radiator.
Fleet Mechanic
Joined: Feb 2007
Posts: 1,652
Likes: 79
From: Mooresville, NC
[QUOTE=projectSHO89;19732882]It is unlikely that this truck left the factory with a heater control valve.
Actually, they do -- I owned one (2000 F-250/ 5.4L) that came from the factory with the heater control valve. I also repaired one some months back -- a 1999 F-250 with the same part number.
Actually, they do -- I owned one (2000 F-250/ 5.4L) that came from the factory with the heater control valve. I also repaired one some months back -- a 1999 F-250 with the same part number.
Fleet Mechanic
Joined: Oct 2004
Posts: 1,395
Likes: 105
From: Southern KS
[QUOTE=F350 1990;19733202]
I think the guy meant left the factory WITHOUT a heater control valve.
It is unlikely that this truck left the factory with a heater control valve.
Actually, they do -- I owned one (2000 F-250/ 5.4L) that came from the factory with the heater control valve. I also repaired one some months back -- a 1999 F-250 with the same part number.
Actually, they do -- I owned one (2000 F-250/ 5.4L) that came from the factory with the heater control valve. I also repaired one some months back -- a 1999 F-250 with the same part number.
Hotshot
Joined: Jan 2004
Posts: 19,765
Likes: 1,082
From: St Louis
[QUOTE=super 6.8;19733245]
Unlikely that is what was meant since, if there's no heater control valve, then it cannot cause the OP's symptom of diminished heat at highway speed.
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New User
Joined: Feb 2021
Posts: 1
Likes: 0
Did you install aftermarket heater core. I have seem several cases were aftermarket heater cores on Ford would not put out hot heat when temperature drops into teens and lower. I would go back with motorcraft heater core.
Freshman User
Joined: May 2018
Posts: 28
Likes: 0
Check your bottom radiator hose. Hoses often soften with age and can sometimes collapse (water pump suction side) when running at a constant rpm for a duration (highway driving), as opposed to stop and go driving in town. This could explain why you have heat when driving in town and not on the highway.
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