Heat

[1969K10]

Ok, I'm not getting good heat out of my truck when it gets below ~35-40 F (for you Canadian members) But it'll sweat you out real quick above that. I rebuilt the heater core a couple weeks ago. Cracked the top hose tube setting the timing & tweaking the carb. I think it is flowing good, any way to check? I replaced my thermostat incase it wasn't working good. I have a 4-core radiator. What's the chance that I just have too much radiator, and need to shut some of it down for the winter?

[JimKshortstep4x4]

A high temp thermostat should keep your engine warm enough (195 degrees)
without resorting to blocking the radiator. I have had good luck with the AC Delco thermostats. Some brands just don't seem to work like they should.

Jim

[1978steven]

I had the same problem with my '71 and a buddy of mine told me to check the coolant level. It looked good when I opened it up, so he said start it. We let it run with the radiator opened and get up to normal temp and we both noticed a couple of bubbles come up in the rad. Then the level dropped a little bit so we filled it some. We repeated the process for about 30 minutes or so till level stayed the same.

I guess when I replaced the thermostat and all the heater hoses I had air in the system still. Now she blows hot air whenever I need it.

[StingRay]

Check to make sure the air mix door is closing all of the way. It's where the cable goes through the firewall under the glove box into the heater core housing. This door controls the mix between hot and cold air. If it doesn't close all of the way when the lever is at full heat it mixes cold air into the hot air stream. The colder it gets the worse this is. Also make sure the hot and cold sides of the heater core are adequately sealed from eachother or the same type of symptom can be present as cold air bypasses the core.

[1969K10]

Thanks for the inputs:
Running a 195 thermo, its a stant - always had good luck in the past.
Will check coolant level, htr door, and seals

Thanks All

[68speedalert]

If your truck in non A/C, check that the hose coming from the intake is going to the BOTTOM heater connector and the upper is going to the waterpump.

Then start it up and crack the upper heater hose at the heater until all the air bubbles stop and just coolant runs out. This bleeds the air from the system.

If you're still not hot enough, when it feels too cold in the truck, stop the truck and let it run. Feel both heater hoses. If they are BOTH hot, you have a blend door problem or air going around the core, like stringray mentioned.

If the lower is hot and the upper is much cooler, you have a flow problem or a restricted core.