They make lots of nice products for cleaning radiators, one I think is call foaminator or some such similar, produces a thick foam that pushes dirt through the fins. But one of THE best and cheapest is dishsoap, I'm partial to duck degreasing dawn. I'll get tractor paint out of your hair and beard FYI. Be easier to clean with the fan shroud out of the way, mix up some dishsoap and water, heavy on the soap and spray it from the engine side. Don't use too heavy a spray to rinse it or you risk damaging the fins.

As far as heat, are all your vac lines in good shape? Ones in the dash arent as easy to check. Have a vac tester? Harbor Freight has a cheap brake bleeder/vac tester combo, could have a bad vacuum... uh what do they call them, actuators I believe. Have you checked to see if you have good flow through the heater core? If it's clogged that could indicate you do have sediment issues in your coolant system. Don't remember if I asked. Did you flush the radiator when you changed the coolant, and did you use distilled water when you refilled it?

Do you by chance have a temp probe to check your coolant temp? New temp sending unit is cheap enough, but its in a difficult spot.

 

I did not read every detail but it does sound like you have air trapped in the system.
When I install a new Tstat I drill an 1/8" hole in the washer part to let air pass thru it the little bit of water that may pass will not hurt a thing.
If the Tstat gets mounted to the front of the manifold or head like on the 300 six put the hole at the top where the air will be.

When you full the system I like to get the front of the car / truck up as high as I can to get the air to the highest point the radiator.
Leave the cap off and start the motor and let it get up to temp. Felling the upper hose when it gets hot and the level drops the stat opened.
It may push a little coolant out or drop down or both. Top up the coolant and let it run more so the stat opens a few more times.
Is the heater turned to hot?
You can lower the front after it opens a few times and let it run more. Put the cap on it and take it for a drive and all should be good.

Now if you go checking the level when cold you will not see it right at the top it will be a few inches below and that is ok but you should see the level.
Dave ----

 

Think about it a little bit. A bleed screw in the top of the thermostat housing is on top of the thermostat. That would do you no good, the air is trapped under the thermostat and the top of the engine. I bet the intake manifold area is completely dry and full of air. Older american cars didn't usually have bleed screws. You can help the situation out a little bit by pull the highest heater core hose off and filling the radiator till coolant starts coming out of the engine there, and then quickly putting the hose back on. Don't pull the heater hose off the core at the firewall, it's too easy to damage the heater core. You always cut the hose off the heater core, never twist and pull it off.

Even with pulling the heater hose off, you will still have some air in the top of the engine.

 

 

To fix the cable? The radiator quit overflowing correct?

 

 

Your top radiator hose should get so hot you can't hold onto it for very long. Your heater hoses also. If one is getting just warm and the other is barely warm or not warm at all, your heater core is clogged. You can drain the coolant again (you do not have to drain it all, just a gallon or so) and pull both heater hoses off the engine. Get a garden hose and stick it on one of the heater hoses and try and flush it out. Grab the other heater hose and flush it the other way. Sometimes this will clear it out, sometimes you have to replace the heater core.

You will get better and better at draining and refilling the coolant. on this old truck. There will always be something leaking or needing service.

 

 

Wow, sounds like you're making a lot of progress. Keep chipping away at it.

On my truck, the temp gauge settles in at the O in NORMAL. The heater output? It will roast you out of there. My wife, who suffers from digitalis popsicallis, loves the truck in the winter.

If your temp gauge barely reaches the normal band, that sounds like a defective thermostat. Before you insist the part is good because it's new, let me plug in my electric violin so we can all sing along on the chorus. I also need to warm up my silk screen press, as I'd like to sell custom printed T-shirts for the event, too.

The preceding was industrial strength satire. All I'm trying to convey is don't assume a part is good just because it's new. I've had plenty of parts bad from stock. Thermostats are one of the worst. I've learned the hard way to always test a new thermostat before installation. It's easy to do, suspending it from a piece of wire in a big pot of water on the stove. Measure the water temperature as the pot heats up. The thermostat should be fully open at the rated temperature.

 

@ctubutis What's the policy on repping for laughs? This is the third or fourth time I've refrained because I don't know. Apologies for being irrelevant.

 

KR does come up with some good ones

Back to our program:
How hot is the upper radiator hose getting by feel?
Then check the 2 heater hoses do they feel the same temp as the radiator hose?
If they feel the same but not getting heat have you checked on cleaning the face of the heater core?
I know the AC trucks et a lot of junk down in there and block air flow wonder if yours could be the same?
Also IIRC the heater temp control is a door that moves could the arm be moving but not the door?
Dave ----

 

The policy is that you need to distribute a certain number of rep points to other users before you can re-rep any one person. I seem to remember the number being 10 at one time but I don't know if it's still that way.

The rep system we have here is due to be replaced with a Like system but that change keeps getting delayed.

 

Um, you do realize it's considered poor form to encourage me, right? Before you know it, my head starts swelling and I'm trapped indoors for a while because I can't get my cranium through a standard doorway.

All seriousness aside, back to the low heat situation. There are many possible scenarios that could be at play. I mentioned low coolant temperature (from a defective thermostat) because that is one of the more likely ones.

However, it could be something else, perhaps a combination of two faults. Let's say coolant temperature is actually normal, but the indication system is reading low. Meanwhile, the heater core is coated internally with scale, or blocked externally with pine needles, leaves, a small rodent nest, etc. Either way, heat isn't getting transferred from the coolant (plenty hot) into the heater plenum. The end result is low heat.

So if you really want to be sure, before loading expensive items into the parts catapult (Pull!), check the actual coolant temperature. Beg, borrow or steal an infrared thermometer. An el cheapo model will work just fine, maybe set you back $20. With the engine fully warmed up, check the temperature on the metal at the radiator inlet. It should be pretty close to the rated temp on the thermostat. If not, the thermostat most likely isn't opening fully.

If the actual temperature is close to the thermostat rating, then you can branch out from there. For example, turn the heat setting and fan to high. Compare the two heater hoses. If you're getting normal heat transfer into the cabin, you should see a drop of approximately 30F. Less than that, and the heater core may be blocked externally (poor airflow) or internally due to scale buildup. Scale buildup inside a heater core acts like insulation, and limits normal heat transfer into the cabin. Note I didn't say just rush out and replace the heater core. To recap, make sure the coolant temp is normal at the radiator inlet. Then compare the heater in and out lines. Then check for external blockage. Only after that should you replace the heater core.

 

My money is on rats nest in the heater core, last two I opened up had them, but they did sit for years it looks like.