Heat sucks

[clemsonteg]

Originally Posted by Longhorn 70

There may be one more thing. Do you have a heater control valve installed? There are 2 different types. One made for our trucks that vacuum closes the valve and the other made for different years and cars where vacuum opens the valve.

If you have a valve that doesn't allow flow through, the hoses will still get hot but the core won't. If you have a valve in place, try bypassing it by placing a short section of pipe in the hose where the valve is.

If you DON'T have a valve, nevermind.

Thanks for the input. No valve. Hoses run directly from the motor to the heater core.

[Longhorn 70]

At least it ruled that out....

Best of luck buddy.

You COULD always move out here to AZ. Then you'd hardly ever need the heat.

[67swb72klb]

Did you check for flow through the core with a water hose if not try it but reverse the flow also

[MattPSU]

How hot is the engine getting? If there isn't much heat in the system, it's not going to put out much heat. When I lived in Pennsylvania, I had to put a piece of cardboard in front of my radiator in the winter so that my heater would blow hot air. Without it, it would just blow cold no matter how much it ran. It would only get warm when the truck was sitting still - when cold air wasn't being forced across the radiator, cooling the system. Might be worth a shot to just try putting a piece of cardboard between the radiator and the grill. Watch your engine temps, and don't forget to take it out when spring gets here. Good luck!

[clemsonteg]

Thanks for the replies. I confirmed that the hoses are connected correctly with the help of the service manual (see picture below).

Both hoses are uncomfortably hot to the touch (when idling). I have a 195*F thermostat (1 year old), and I can feel the upper radiator hose get hot after several minutes of running.

I have checked that water flows through the core (at least part of it) by running a hose both directions. The only item I can't rule out completely is a partial blockage inside the core.

I plan to elevate the front end of the truck this evening and run the engine to positively rule out air in the system. After that, the only item left I can check without removing the core is blocking the radiator as MattPSU suggested. The engine is a crappy 72 307 and the radiator is a new all copper 3 core. Maybe its too much cooling capacity.

[Boog]

I may have missed it but is there good airflow from the vents? If both heater hoses get nice and hot i believe I'd go under the dash and watch the control cables as I moved them back and forth especially the temp control lever. Maybe take that cable loose at the heater case and move that door by hand and see if the temp improves.

[hamjet]

X2 what Boog said..

[clemsonteg]

Originally Posted by Boog

I may have missed it but is there good airflow from the vents? If both heater hoses get nice and hot i believe I'd go under the dash and watch the control cables as I moved them back and forth especially the temp control lever. Maybe take that cable loose at the heater case and move that door by hand and see if the temp improves.

I have verified that the blend door is opening and closing as it should. Not quite sure what to consider "good" air flow, but it seems adequate. It is certainly more than a small wisp of air from the floor vent or defrost vents

[hamjet]

From defrost to floor heat is one blend door that has nothing to do with heat, the other has to do with outside air to just from the heater core. I think thats the one Boog is referring to. Is that the one you say opperates good?

[Step-Ed]

Great thread......my hoses are not correct connected.

[clemsonteg]

Originally Posted by hamjet

From defrost to floor heat is one blend door that has nothing to do with heat, the other has to do with outside air to just from the heater core. I think thats the one Boog is referring to. Is that the one you say opperates good?

Sorry, I typically refer to the blend door as the one which controls the temperature. In my case the door either allows air to bypass the heater core (open on the inside of the cab), or forces air through the heater core. I have checked the operation through the inspection port and it I'd working correctly.

[Andy4639]

I still say put the inlet on bottom to take care of any air pockets.

This is my old TPI motor water lines. You maybe right on the lines but I would still run the intake to bottom of heater core then top out to water pump. As I stated I have always had AC truck so I followed this drawing out of the service manual.

[clemsonteg]

Originally Posted by Andy4639

I still say put the inlet on bottom to take care of any air pockets.

This is my old TPI motor water lines. You maybe right on the lines but I would still run the intake to bottom of heater core then top out to water pump. As I stated I have always had AC truck so I followed this drawing out of the service manual.

Thanks Andy. As mentioned previously and in the drawings, I have the intake going to the bottom of the heater core and the exit from the top of the heater core to the water pump.

Was the picture you posted in post #19 one of your motors as well? It has the hose connected with the inlet to the top and exit to the water pump.

[Andy4639]

Nope that was just one I pulled off google. I thought I had some pictures of my old 305 TPI hoses routed but I can't find them. Why do you think the heater core maybe blocked if you got a good stream of water out of it. I assume you flushed it both ways right!

You also said you have a 195* stat so that should be plenty. The hoses getting hot means the system is working. If you run the truck with the cap off try to put the front of truck on jack stand are at least jack it up to help remove the air pocket which is what I think you have. Putting cardboard in front of the radiator is fine but keep a close eye on it. Don't let it over heat.

[davepl]

Good one on the heater hose valve! That'd have been funny... Non-AC though I think.

I'm just going to throw out a couple of troubleshooting things I've run across as the years have gone by. Might help here, might help someone later, might never help!

First, when you check the hoses going into and out of a heat exchanger in our vehicles you can't conclude very much. For example, in the Saskatchewan winter I had the HOT light come on. I assumed must be the thermostat was stuck shut. But the upper rad hose was plenty hot and in some cold-start-warmup testing it got hot at about the time the thermostat should open.

So, with the thermostat ruled out I chased a lot of things. New water pump. Flushed block, flushed the radiator, and I don't remember all what else. But I do know it was -30F and I was working in my Dad's dirt driveway laying on cold, cold ground to do all of this.

In the end, it was the thermostat. Enough hot water can get by even a significant restriction (like a stuck thermostat) to make the hoses appear like its flowing even if they aren't. In this heater core case, you can't tell a whole lot just by knowing the two hoses are hot.

Also, I think it'd be hard to determine, by hand, whether the core was good by trying to detect a temperature difference between input and output. With a thermal gun (cheap now, everyone should have one) you might. But what's the right drop? Who knows?

What you -could- do would be to measure the temp change with the gun with the blower off. Then on Medium. Then on High. If the core itself is allowing are to pass through it, you should see a BIGGER drop on high than medium and off. That tells you the airflow part.

I'd then pull both hoses off and flush it in-place. If you have compressed air, set your regulator appropriately and, without plugging it (remember, they only live with 16psi even on a bad day) blast air through it. Protect yourself and be ready for a mess. Then you could also blast your garden hose through it to make sure its really flowing well (but a garden hose can be 150psi too).

If you have access to it, a new core is good insurance anyway (but buy a quality one, or recore a Harrison original).

[imjeff]

No need to mess with the radiator. Your heater core gets water before it goes to the radiator. You may have just enough buildup that you're not getting good heat transfer. If both hoses are hot you have flow so either have the core repaired by a good shop or replace it.

Jeff

[clemsonteg]

Thanks everyone. I flushed the heater core again tonight. Not much debris, at least not enough to cause a significant clog. I dropped all the air out of the rear bags and inflated the fronts all the way. I also jacked up the front as high as I could. I was able to squeeze another half gallon or so of 50/50 into the radiator.

I think my issue may be a compound of a few issues. I think my engine runs on the cool side, especially when it's moving with air flowing through it (see picture of my temp gauge below). I noticed with a piece of cardboard blocking the radiator that the gauge moved further than I have ever seen it, maybe to 1/3 the way between C and H (assuming the picture shows around 1/4).

[Andy4639]

That picture shows a normal reading on a stock 307. Is it getting any hotter inside the truck?

[clemsonteg]

Originally Posted by Andy4639

That picture shows a normal reading on a stock 307. Is it getting any hotter inside the truck?

It's hard to say. It's always warm idling in the driveway. The real test will be driving it down the road.

[Andy4639]

You do have all the cab vents closed and any holes in the fire wall sealed up.
Both the kick panel vents need to be closed off.
Driving it shouldn't make any differance unless you have a lot of holes letting in cold air. Once the truck is warmed up it should stay. Does the needle go down on the gauge once you start driving it? The gauge is motor temp not radiator temp.

[clemsonteg]

Originally Posted by Andy4639

You do have all the cab vents closed and any holes in the fire wall sealed up.
Both the kick panel vents need to be closed off.
Driving it shouldn't make any differance unless you have a lot of holes letting in cold air. Once the truck is warmed up it should stay. Does the needle go down on the gauge once you start driving it? The gauge is motor temp not radiator temp.

Vents are closed. No holes to speak of. I need a new column seal, but I was waiting to do my auto swap for that. There isn't any insulation in the cab to speak of either, my floors are bare. When I notice cooler temps in the cab while moving its actually air blowing from the vents. All based on my calibrated hand of course.

[Longhorn 70]

Hmmm from which vents? The only one that should be blowing out heat is the bottom vent or the defrosters if in defrost mode.

[clemsonteg]

Originally Posted by Longhorn 70

Hmmm from which vents? The only one that should be blowing out heat is the bottom vent or the defrosters if in defrost mode.

The fresh air vents are closed on the kick panels. I usually have heat blowing from the floor vent. Heat rises sort of thing.

[Longhorn 70]

ah I keep forgetting this is a NON AC truck...duh

[my67c20]

So let me get this right, no insulation, current temperature of about 25 deg, with a high of around 50 deg. First off air is a poor conductor of heat. With that said, the warm air, cause that's about all your getting at those outside air temps, is mixing with the cold steel and air contained near the floor, causing you lower extremities to feel cool, which in turn sucks the heat from your core body temperature, which eventually makes everything feel colder. I would suggest getting some type of carpet, even if it is only one of those carpet squares that have some insulation on the bottom, as a temporary measure to make things feel warmer. From reading the thread, it seems your system is working properly, but you not only have mother nature against you, but also air fighting general issues with air. Just me 2 cents.