Heat sucks

[clemsonteg]

So the heat in my 70 C10 sucks. Always has. So far, I have replaced the thermostat, radiator, and all the hoses. Both hoses on the heater core are hot. I tried flushing the heater core with water and I didn't see any debris. I had the heater box off a few months ago and I cleaned out all of the leaves before I re-installed everything. I also checked that the blend door is opening and closing as it should.

I am sort of out of ideas. The only item I can think of would be a partially blocked heater core. Can anyone suggest flushing solutions/techniques other than water?

[boynton]

The only thing left in the equation is the heater core. if you plan on keeping the truck for a while, I would just cough up the extra money to buy a new heater core rather than a temporary fix. If your heater core is that clogged up, it may start rusting out soon (or it already has) and that will be a problem in the future.

[clemsonteg]

Originally Posted by boynton

The only thing left in the equation is the heater core. if you plan on keeping the truck for a while, I would just cough up the extra money to buy a new heater core rather than a temporary fix. If your heater core is that clogged up, it may start rusting out soon (or it already has) and that will be a problem in the future.

Considered that, but I am hoping to do an aftermarket AC/heat system later this spring. I was hoping for a solution in the meantime so I can still cruise the truck for the next few months

[Lee H]

How do you have the hoses routed? Intake to bottom of core, top of core to radiator or water pump.

[clemsonteg]

Originally Posted by Lee H

How do you have the hoses routed? Intake to bottom of core, top of core to radiator or water pump.

I sure do. Intake below the thermostat goes to the bottom, top goes to the water pump

[Lee H]

Just checking, I've seen lots of pictures lately with the heater hoses routed the opposite way.

[clemsonteg]

Originally Posted by Lee H

Just checking, I've seen lots of pictures lately with the heater hoses routed the opposite way.

I appreciate the input. It was one of the items on my list and I came close to installing the heater core upside down when I had everything apart last year

[JimKshortstep4x4]

Have you felt the hoses to see if the coolant going to the heater core is hot? Also, if your system is low, the coolant circulating to the heater core is the first to stop moving.

Jim

[clemsonteg]

Originally Posted by JimKshortstep4x4

Have you felt the hoses to see if the coolant going to the heater core is hot? Also, if your system is low, the coolant circulating to the heater core is the first to stop moving.

Jim

Hoses in and out are both hot to the touch. The heat is mildly warm when stopped for a period of time. Once the truck is moving the air cools off again. I have topped off the coolant and ran the truck several times without the radiator cap to burp the system. The minimal heat when stopped sort of makes me think it's a partially clogged heater core

[1972BlueC20]

I know this isn't your problem, but in case others are having heater problems and see this thread......i had a new engine installed recently and the mechanic ran my hoses from radiator to core, then from core to water pump.

My heater wouldn't get over about 70 degrees this way.

I plugged the radiator port and routed from the core to the intake and from the water pump to the core as described above, and this thing is scolding hot now!!!

Heater cores aren't hard to change but just time consuming.

If heater only truck, unbolt the passenger side hood hinge bolts, unbolt the passenger side fender well...let rest on tire....this will gain you access to the lower bolts on the heater box...unless your bottom bolts are already missing from a previous replacement. Then reverse to put back together.

I went ahead and replaced my blower motor and fan blade wheel and resistor while I was in there just for good measure....it was all relatively cheap and just wanted to get it all done while I was fooling with it.

It also gave me a chance to clean all the debris out of the heater box and I installed some new gaskets for the heater box.

[mechanicalman]

Originally Posted by clemsonteg

Hoses in and out are both hot to the touch. The heat is mildly warm when stopped for a period of time. Once the truck is moving the air cools off again. I have topped off the coolant and ran the truck several times without the radiator cap to burp the system. The minimal heat when stopped sort of makes me think it's a partially clogged heater core

I'm thinking that the inlet heater hose should be hotter than the outlet, during heater fan operation.

If it isn't, then the core must not be transferring heat.

Get a new core, and only use coolant that has no tap water in it (distilled only). If you have tap water in the system now, drain it all and that includes draining the block (both drain plugs under the exhaust manifolds)(install radiator pet-cocks if you are keeping it). If you need new coolant, install the 50/50 pre-mix to assure you get mineral free coolant.

Never put tap water in your system.

[EARNHARDT#3]

Heater cores are only like $30.

[72MARIO]

If you think your heat sucks now just wait till you swap a aftermarket ac system. The old air heat ac system was so bad my suburban got parked in September this year !

[boynton]

part of the problem may not be the water flow in through your heater core but rather the air flowing through it. If the heater core is stopped up on the outside and air is flowing around it rather than through it this would also cause your problem. This is also a common problem with home heating/ac units. Debris such as dirt/hair will clog up the fins over time causing air to not be pulled through the core but around it. I know they make a spray to clean the debris but you would still have to remove it and if you go that far you might as well replace it. One solution might be to try to get an air blower on the core and blow the dirt off of it.

Good luck!

[Andy4639]

Originally Posted by boynton

part of the problem may not be the water flow in through your heater core but rather the air flowing through it. If the heater core is stopped up on the outside and air is flowing around it rather than through it this would also cause your problem. This is also a common problem with home heating/ac units. Debris such as dirt/hair will clog up the fins over time causing air to not be pulled through the core but around it. I know they make a spray to clean the debris but you would still have to remove it and if you go that far you might as well replace it. One solution might be to try to get an air blower on the core and blow the dirt off of it.

Good luck!

Very good point. If the truck has the orignal heater box and you have never taken it a part would be a good time to and clean it out good. I don't see any reason to buy a new heater core though just because, but depending on how it looked when you take it out.
My first 67 truck burnt to the ground after I boought it. I bought that spring no problem, that fall the first time I drove the truck with the heater on it caught on fire from all the pine needles inside the box.
Just a note. A non AC heater box is a easy job compared to a AC box!

[Ironangel]

Originally Posted by boynton

part of the problem may not be the water flow in through your heater core but rather the air flowing through it. If the heater core is stopped up on the outside and air is flowing around it rather than through it this would also cause your problem. This is also a common problem with home heating/ac units. Debris such as dirt/hair will clog up the fins over time causing air to not be pulled through the core but around it. I know they make a spray to clean the debris but you would still have to remove it and if you go that far you might as well replace it. One solution might be to try to get an air blower on the core and blow the dirt off of it.

Good luck!

+1...Take the outer box off and clean things up, you'll be surprised at what's clogging the fins...Make sure the cable operated interior doors (air flaps) are opening and closing properly as well...

[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.

[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.

[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]

X2 what Boog said..