Winter. Need heat from the heater.

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Episode #356 of "still trying to put the old gal together".  Dec 23:  brrr, it's cold outside and so have to turn to getting some heat out of the HVAC system.  As is, blower works good, air comes out of the right openings (matches what the controls are set at) but the temperature control provides the same temp regardless of setting, "tepid". 

I know moving the temp lever is supposed to change a door in the heater box *and* activate a vacuum driven valve under the hood.  Observing the heater box I can see the cable move and hear a door change position; the only question there is the valve controlling the hot water under hood.  But also, the (factory) temp gauge never moves off the very lowest of the "normal range" (heat sending unit was new this year) and after reading through the recent long discussion about thermostats, I started questioning if the engine was actually getting hot.

So I drove around for about 20 minutes (outside temps in the high 50s, speeds up to 50), took the dog to the dog park for 15 minutes then drove 2.5 miles home (slight incline up the hill).  Once home I waited 10 minutes as the manual recommends before releasing the pressure before removing the radiator cap, then stuck in an instant read thermometer.  133F.  Seems low to me; hard to believe it would drop 50 degrees in 10 minutes if we'd reached normal operating temperature.

Although I replaced the 180F thermostat when I did the water pump two years ago, I couldn't remember if I'd put in the brass flow restrictor, and I'd never tested the thermostat.  So I pulled the thermostat and tested it in with a pot of boiling water:  seems to work fine.  And yes, brass restrictor valve is there.  Forgot the paper gasket would be trashed so got the replacement today and am about to put the thermostat back in.  99% sure the thermostat is not the problem.

Next I'm going to see if I can manually trigger the vacuum gauge on the hose under hood, and if that changes the temp coming out of the heater.

But I want to put this all out there to see what the hive mind thinks and/or recommends about the low engine temp, the recalcitrant heater and the gauge.  Whew.

Photos:  Left, cold engine, just after starting.  Right, warm engine after 20 min > 1500 rpm.  This is as high as it ever goes.

73 Mustang Temp Cold and Hot.JPG

 
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Because the radiator cap is at the opposite end of the radiator from the upper hose the coolant has already passed through the radiator and will be much lower than the coolant in the engine, especially at this time of the year.

Get an infrared thermometer from Harbor Freight and see what the temperature is at the upper radiator hose connection at the radiator when you first start it and then at regular intervals.

Infrared Laser Thermometer (harborfreight.com)

The temperature should stay low until the thermostat opens up. If the temperature rises gradually the thermostat is defective. When it opens the temperature should be within 5 degrees of the rated temperature. You can also measure the temperature at the thermostat housing, just have to make sure you're measuring coolant temperature and not block temperature.

You're on the right track by testing the vacuum controlled valve, with a vacuum pump, at the valve.

 
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All others would be happy to have such low temperatures on their cars and not overheating  :biggrin: :whistling:  

But if all other things are fine it could be a false temperature sensor and/or the gauge however. It would be interesting if you have a spare sensor and gauge what they would read... 

Do you have a temperature reader, such a pointer with which you could read the temperature off of the display when pointing with the laser to a spot? So you could go through the entire cooling system when your car is running and eleminate possible faults. 

Edit: 

Ooops, Don was faster. I meant the infrared thermometer he states, thanks for chiming in, Don.

 
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I don't know if this will help you but here is some info on the vacuum lines and what vacuum motors should be doing what based on your temperature control settings.  I think these are good for all 3 years.

 AC - Heater Vacuum Lines - Motors.gif

Vacuum Motor Testing.pdf

Vacuum Testing 2.pdf

 

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Hemikiller

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Simplest way to test if the water control valve is malfunctioning is to remove it from the system and inspect it. I've had plenty that were damaged and stuck either open, or closed. There's a plate inside the valve that should close when vacuum is applied. 

Install a connector between the two hoses and see if your heat improves. You could also have a partially obstructed heater core, either internal or external. 

 
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Something else to check - I pulled this from a 32016 Post by Don C:

The hose that is connected to the block is the pressure hose and should run to the inlet connection on the heater core, which is the one on the lower left. The hose connected to the water pump is the return line. If the hoses are connected wrong there will be an air pocket in the heater core that will prevent coolant flow through it. The other possibility is that the heater core is plugged, which is not uncommon.

I had this issue with mine - could not get any real heat out in the winter, and when I found this post, moved the heater hoses accordingly - fixed my heater issue right away.

 
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MooseStang

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I'm dealing with a similar but opposite problem, but with A/C.  In fact, I just bought some vacuum hose for the water valve yesterday.   

The diagram posted shows this line as purple.  Does purple actually show somewhere?  How long is this line? (I only bought 4')

 
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73inNH

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Simplest way to test if the water control valve is malfunctioning is to remove it from the system and inspect it. I've had plenty that were damaged and stuck either open, or closed. There's a plate inside the valve that should close when vacuum is applied. 

Install a connector between the two hoses and see if your heat improves. You could also have a partially obstructed heater core, either internal or external. 
OP - I went through this exactly thing during the Fall. In my case, it was exactly as hemikiller described. The heater valve was stuck closed so warm radiator fluid never flow to the heater core. I took the valve out, soaked it into vinegar, and it returned to normal operation. However, I believe the spring that closes it is a little bit weak, as sometimes even when I turn off the heat, I can feel a little coming out. Many of the replacements, however, are cheap plastic. For this reason, I've opted to keep the original for now.

 
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Per DonC's test recommendations above, temps at the hose leaving the block for the radiator using an infrared thermometer gun:
61F -- outdoor temp
115.7F -- not running, one hour having been driven 17 miles (roundtrip to Sonic)
108.0F -- right after starting
155.6F -- after 10 minute drive on neighborhood streets
177.4F -- after 3 miles in slow traffic to get gas and return home

So, would seem normal operating temperature for the engine.

The (factory) temperature gauge was below "C" until after the ten minute drive where it got up to the outer edge of the low end of the middle scale, then after returning from getting gas, was just to the inside edge of the low end of the middle scale. Seems to me either the gauge or sender is faulty, and I'm guessing the gauge because the sender is new..

And this originally started out about the heat. I could not get the under-hood vacuum motor to budge with direct application of vacuum. It would move with finger pressure, but didn't return to any position when the pressure was removed, nor did it move with vacuum after being moved by finger. I replaced it and now I get heat out of the heater - yay. But, it is plastic as 73inNH noted, so I'll keep the old one around.

Now pondering the temperature gauge. I could kinda be ok with it if there were a warning light, but there isn't. And I'm trying to keep the original look. Hmm.
 
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You can put an Autometer Pro Lite Temperature Switch on the engine and just wire a small light to it that you can put anywhere in the dash. These switches come in different temperature ratings. A 220 degree one will complete the circuit at 220 degrees and you can light up a light with it. It will not go off till you get under 190 degrees. Here is the sender:
 
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