Why do i keep getting lukewarm air

[king01]

I’ve about had it with this. Have changed my thermostat, coolant is good, purged the system everytime now and unclogged my heater core 2 weeks ago. Was working perfectly fine for about a week before it went bad again. If I accelerate heavy it does heat back up but then goes lukewarm. Is it possible for my heater core to have gotten clogged again?

 

[Hamfisted]

Are you getting reliable heat at the rear vents ? The rear has it's own heater core, and no control valve to interfere with flow, supplying constant hot coolant to the rear.
Is your hot water valve functioning properly ? ( hot water valve modulates front heat only...) . Have an assistant run the selected temperature up and down while you watch the hot water valve to make sure the valve linkage is moving. Or you can select cold temp on the HVAC panel and pull the vacuum tube off the hot water valve and you should see the arm move to the open position and the heater hose aft of the valve get hot.









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[kep5niner]

Interesting discussion and response, Mike. With the first time I've had my EB in colder weather, I'm questioning the effectiveness of my HVAC / heating system. I did try to test the hot water valve as you outlined above, but it basically did nothing. It never moved throughout the test process. I even zip-tied the valve arm, and noticed no discernable difference in heat output at the vents. The cooling system is sound, no leaks, purged, and I've put over 7,500 miles on the new engine since the summer.

It seems like I should be getting warmer air through the vents. Any thoughts?

 

[Hamfisted]

Kep do you get a good vacuum on the vacuum line connected to the hot water valve with the temperature selected to cold ? It defaults to open if there is no vacuum applied. If you have a vacuum pump, apply a vacuum to the valve and it should close ( you should see the arm move...) . Are the heater hoses hot to the touch on the firewall side of the valve when it's supposedly open ? How's the heat coming from the rear vents when you select a warm temp on the rear controls? It's pretty much a separate system other than sharing the hot coolant from the motor, and no hot water valve to interfere with coolant flow.


Vacuum supply line from manifold .... / ... and sheathed vacuum line up to the hot water valve ....






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[kep5niner]

I'll check the vacuum at the line today and report back, as well as test the valve. Any idea how much vacuum I should be reading from the line? How much vacuum should actuate the valve? The rear heat blows warm enough I suppose. I'll also confirm the heater line aft of the valve gets warm / hot.

For the two lines that go into the firewall, where do they terminate in the cabin? If there is a leak on the cabin side, I understand that is major surgery to access them. All vacuum lines under the hood were replaced with new Motorcraft lines when I installed the new engine. Thanks again for your feedback!

 

[Hamfisted]

You should see about 20 inches of vacuum with full cold selected. Pulling the vacuum tube off the valve you should see the armature move full throw to the open position.
The vacuum tubes run to and from the control solenoid which is under the dash right in front of the center console. You have to remove the center console to get to it, but not the dash.









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[kep5niner]

Checked the vacuum at the vacuum line: zero. I blew on the line as well, and that did not hold pressure either. The heater hose aft of the hot water valve does get hot. Looks like I'm taking out the center console. Thanks for all of your input and help Mike!

Pete

 

[Hamfisted]

Is the vacuum supply line intact going into the firewall grommet ? It's common for it to break with age. The hot water valve vacuum line doesn't seem to break as often for whatever reason. I think people drop the battery on the supply line when they replace batteries or something. Do you have a little handheld vacuum pump you can test the hot water valve function with ?


Mechanics Handheld Vacuum Pump Kit on Amazon



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[kep5niner]

I did grab a hand held vacuum pump, kind of like the Mighty Vac. That’s how I tested the hot water valve vacuum line, which yielded zero vacuum indication. I’ll have to see how I can make the connection to the actual valve to test that functionality.

The lines going through the grommet at the fire wall look sound, but looks can be deceiving. Maybe I’ll have to hook up the smoke machine to see what I can see.

I did pop off the center console, and the solenoid looks like it’s buried toward the front. I’ve got tomorrow to fool with this, then it’ll be parked for a week while I’m at work.

 

[kep5niner]

While I was in the truck, I did run the DATC functions self test and checked for DATC DTCs. Self test was good to go, and no DTCs appeared.