No heat!

Rainmaker · Dec 10, 2017

Winter hit hard in Minnesota last week, about 8 degrees and the first time I needed to use the heat and got lukewarm air at best. I noticed the temp gauge was wandering up and down so I just replaced the thermostat. Drained and refilled the radiator in the process. Now the temp gauge won't go up unless I turn on AC or turn off completely (blender door closed). As soon as I try to blow heat the temp gauge starts dropping and I never get heat. Before I replaced the thermostat the upper radiator hose was hot and the heater core hoses seemed to be acting appropriately (one hot, other warm).

Help please, I'm fine with bundling up but not having warm defrost is downright dangerous.

RonD · Dec 10, 2017

New thermostat is stuck open or the wrong one

Correct thermostat is 192 or 195degF, but some use 205degF on the 4cyl Limas in cold climates

If you got a 180degF that's the problem.

Spring on a thermostat goes into engine side, thats the part that needs to warm up.
Lima engines bleed heat pretty fast, many also use cardboard in front of rad during winter months, cuts air flow into engine bay to keep block and heater hoses hotter.

You can also wrap heater hoses with pipe insulation to keep them hotter

Rainmaker · Dec 10, 2017

The thermostat I installed was a 190 degree, only other 2 I see readily available are 192. Drove about 45 miles home without heat, neither heater core hose is very warm. Upper radiator hose is only moderately warm.
Does this seem in line with your theory?

tomw · Dec 11, 2017

I would bet a nickel the thermostat is not seated tightly into the housing, and is allowing coolant to flow. The upper hose should not even get warm until the engine is up to temperature. (Well, the hose leading from the thermostat housing towards the radiator.)
A thermostat should not allow coolant to flow at all until it opens. Warm means it is allowing coolant flow below normal opening temperature.
When the flow is good, BOTH heater core hoses should be too hot to keep touching. If one is hot, the other warm, the flow is not enough. It may be the core is plugged or needs to be flushed. I'd work on the thermostat first to see if the flow would improve with the thermostat seated and functional.
I would suggest a brand name stat. Stant, Robertshaw, Motorcraft, but would pass on the 'house brands' that are questionable. The legs of the stat may need to be 'arranged' to place the stat and keep it in position. Lima stats had flat feet on the legs that fit into a depression next to the gasket seating surface to allow the housing to seal. Bend to fit, and make sure the rubber gasket seals against the outlet. The flow should ALL pass through the stat opening, not go around. You should not be able to see light if you held the housing up to a light, outlet towards the light.
tom

RonD · Dec 11, 2017

190degF should be OK, but just OK

Yes, feel upper rad hose just after startup
Then feel it again after 2 or 3 minutes, should still be COLD as should radiator

Radiators purpose is to get rid of "extra heat" generated by the engine, on a cold day it may never warm up because there is very little "extra heat" in the engine.
Heater core is part of the engine system so should get as hot as the engine coolant.
Which should be minimum 190degF after 5 to 8 minutes, normal warm up time.

On Ford Temp gauge 210degF is about 1/2 way, so your should read above 1/3 but below 1/2 if things are working as they should

Rainmaker · Dec 11, 2017

Thanks guys, I tried checking hoses again this morning after a very unpleasant drive to work (wet snow falling on and instantly freezing to my windshield), there is a marked difference between the inlet/outlet of the heater core. It'll be a couple days until I'm able to get somewhere with a garden hose to flush this thing but I think that may be the culprit. I'll check the seat on the thermostat as well but I think I got that thing mounted pretty solid. Hopefully the weather holds out a little better until then..

Just FYI, I did opt for the motorcraft thermostat. Odd that the cheapies were 192 but the only motorcraft option the store had was 190...

RonD · Dec 11, 2017

Put garden hose on the Colder hose of the heater core, so you will Back Flush the core.
That will hopefully push out any larger debris the way it came in.

Also blow out the core as best you can and then refill with a hot water/CLR mix, let it sit for 15-20min then back flush again.
Repeat as you see fit

Rainmaker · Dec 12, 2017

Since it was going to be a few days before I'd have a chance to do this myself I bit the bullet and brought my truck to the garage across the street from my work to flush the heater core. The mechanic said he blew out a whole lot of debris and sludge, went back and forth about 12 times before getting it to run clear. Drove it home and heat works perfect, money well spent. Good thing-it was 7 degrees outside when I started it up this morning...

Thanks again for all the help.

RonD · Dec 12, 2017

Good work

Thanks for the update and fix

No heat!

Rainmaker

New Member

RonD

Official TRS AI

Rainmaker

New Member

tomw

Well-Known Member

RonD

Official TRS AI

Rainmaker

New Member

RonD

Official TRS AI

Rainmaker

New Member

RonD

Official TRS AI

Sponsored Ad

Sponsored Ad

Staff online

Members online

Member & Vendor Upgrades

Latest posts

Truck of The Month

Recently Featured

Follow TRS On Instagram

Latest Album Photos

TRS Events

25th Anniversary Sponsors

Check Out The TRS Store

Sponsored Ad

Sponsored Ad

Sponsored Ad

Amazon Deals