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1968 coupe, 289, auto, no AC

I have what i imagine is slow heat defrost. But i have never had a 68 mustang. So I may be expecting more than what i have in terms of heat. It does warm up.

Now the real question.

Its 12 degrees out. I wanted to check to see if the supply and return lines to the heater core were warming up. I started the car and let it idle for 10 minutes or so. Both supply and return were hot, almost to the point where i had to let go.

I then checked the top and bottom radiator hose and they were not hot. I then cracked the radiator cap to see if the coolant was hot, but it was not.

Thoughts? Did i not let it run enough to warm up to open the thermostat?
 

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Sounds like you didn't. The heater lines will flow without the thermostat opening. At 12 degrees outside it might take a a little while for your thermostat to open. I would drive it then check the hoses.
 

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Your stock thermostat should open at about 160* and engine operating temp should be in the 200* range. Replace your thermostat and you'll probably get all the heat you want. While you do the thermostat, it would be a good idea to drain your coolant and flush the system. Just slap the thermostat housing back on the engine (with old thermostat removed), open the radiator drain ****, start the engine and run a hose into the top of the radiator for a few minutes. If the fluid comes out rust orange, keep flushing until it's mostly clear. Then put in the new thermostat (right side up), refill the system and run the engine up to temp.
 

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Stock is actually 195. I run a 180 in the South. It rarely gets to 12.... I tried a 160 T stat once and I didn't have enough heat when winter came. There have been a bunch of other posts lately about the same topic, nasty coolant, etc. Read those for my super-cheap white vinegar super-flush.
 

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If BOTH heater hoses were hot enough that you had to let go and you're not getting heat inside the car or from the defroster you probably have a stuck or poorly adjusted blend door or diverter that is not allowing air flow through the heater core or diverting it properly inside the car.
 

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Make sure you get the Motorcraft 190° with the tiny check valve at the top. If you can't, drill a 1/16" hole in the upper part of the flange. This will allow air to escape from the system when you fill it.

 

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I suspect so. I learned that trick from my Grandad, who was an auto mechanic from 1920-1955.
 

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22GT's advice is good - I'll throw in a tidbit as well. The NAPA premium thermostat is identical to the Motorcraft in that it has the little toggle in the hole (as shown in 22GT's photo) but it costs less and is easier to find. I've got one in my car.

The heater on these cars is one of those overachieving types - it should get you toasty very quickly as soon as the motor is warmed up, since it uses coolant directly cycled from the motor. If your heater hoses are hot but you're not getting heat quickly (and I mean scalding hot, I-can-feel-it-through-my-boots heat), then you should check your heater box control cables where they attach to the heater box. Sometimes they will slip off of the posts so the cables don't actually move the doors around inside the box, preventing heat from coming through correctly.
 

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Thanks for the help all. Going to flush and replace tstat tomorrow.
Without an actual problem?
If the heater hoses got hot the WP is working. If the rad and hoses were cool the t-stat hadn't opened. If the t-stat is bad the gauge should tell you. How long does it take 12* water to boil where you are?
 

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Discussion Starter #17
I did some investigation yesterday. I was preparing to flush out the heater core and noticed that the previous owner had installed the coil so it was crushing one of the hoses to the core. Like 80% crushed. Repaired that and all seems well. Sometimes its that simple. Thanks for all the help.
 

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Happy you figured out! For any future being who might stumble over this thread under the search, I had the same problem with my heater never blowing hot air regardless if engine temp and traced it back to using some silvery radiator stop leak that hadn't been well flushed afterwards to get home one time, apparently clogged the whole frickin core. Something else to look into
 

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I need a thermostat and I want to get a Motorcraft one. What are the part numbers for a 180 ( yes I know ) and a 190?

There seems to be part numbers along the lines of RT-xxxx.

Thanks.
 

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That'll depend on what engine you have. According to Ford's parts web site here they list these options for the 3.3L and 4.7L:
RT350 - 1964 - 1968, Mustang, Liter:3.3, Cylinder(s):6, BoreIn:3.68, StrokeIn:3.13, Therm 160;1964 - 1968, Mustang, Liter:4.7, Cylinder(s):8, BoreIn:4.00

RT1167 - 1964 - 1968, Mustang, Liter:3.3, Cylinder(s):6, BoreIn:3.68, StrokeIn:3.13, Therm 190, Thermostat Only

RT351 - 1964 - 1968, Mustang, Liter:3.3, Cylinder(s):6, BoreIn:3.68, StrokeIn:3.13, Therm 180;1964 - 1968, Mustang, Liter:4.7, Cylinder(s):8, BoreIn:4.00

RT1139 - 1964 - 1968, Mustang, Liter:4.7, Cylinder(s):8, BoreIn:4.00, StrokeIn:2.88, Therm 192

I'm sure if you poked around at that site you could probably find the listings for the big blocks too, but that's what it came up with for me.
 
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