coolent heater blowing cold air

[jsthnt@gmail.com]

My coolent heater is blowing cold air. It is in the cab and the engine is getting up to normal tempeture. What do I need to check to fix this problem. Or would it be better to just get an electric heater?

 

[emmado22]

Make sure the valves coming off the block that feed the heater hoses are open.

 

[rosco]

Or you could also have and "air lock" in it. Loosen one or both hose clamps at the heater, and see if some air woun't escape. Try both, so you are sure. Leave the pressure cap on the raditor, so there is some pressure in the system.

 

[WillWagner]

Or you could also have and "air lock" in it. Loosen one or both hose clamps at the heater, and see if some air woun't escape. Try both, so you are sure. Leave the pressure cap on the raditor, so there is some pressure in the system.

That's a dangerous thing to do when you have a cooling system up at pressure and temp. unless you like big blisters on your skin. Do it when it's cool and you can pressurize the system with a pressure tester if you need to.

 

[Bob USNR]

After you have driven the truck until it reaches operating temp the hoses to the "cab heater" should be hot.
If they are not hot after verifying that both valves on the 2 hoses are open then the "heater core" could be plugged up.
To clean this stuff out you will need to disconnect both hoses and use a garden hose to send water through it in the >>opposite direction<< to the normal flow until the water coming out is clear. Then do it in the other direction until it is clear. Keep reversing the flow until it is always clear.

If it was plugged with stuff you will easily see it wash out.
You do not need to remove any part of the heater from the truck to do this. Hold the hoses in your hand and yes you will most likely get wet. I have been doing this "repair" for 45+ years and usually get wet doing it.

One very important consideration here is >do not< get fittings to make a leak proof connection to the heater core. You will most likely blow the core apart rendering it useless.
Most vehicle radiator systems maximum pressure is 14psi. Your home system is at least 45psi on a well or city water systems tend to be about 80psi.


e

 

[sandcobra164]

Most of these heaters have a bleed valve on top of it. When I installed my heater, I started the truck with the radiator cap off and cracked the bleeder till it had coolant coming out and all has been fine. Depending on who installed the heater, it could be tied into the wrong passages on the motor, there's an old PS article concerning this. The top hose is plumped into the thermostat housing on the motor, not radiator side of the thermostat and the bottom plumbs into the water pump and you have to move the generator out of the way to open and close the petcock on it.

 

[aaron379]

After you have driven the truck until it reaches operating temp the hoses to the "cab heater" should be hot.
If they are not hot after verifying that both valves on the 2 hoses are open then the "heater core" could be plugged up.
To clean this stuff out you will need to disconnect both hoses and use a garden hose to send water through it in the >>opposite direction<< to the normal flow until the water coming out is clear. Then do it in the other direction until it is clear. Keep reversing the flow until it is always clear.

If it was plugged with stuff you will easily see it wash out.
You do not need to remove any part of the heater from the truck to do this. Hold the hoses in your hand and yes you will most likely get wet. I have been doing this "repair" for 45+ years and usually get wet doing it.

One very important consideration here is >do not< get fittings to make a leak proof connection to the heater core. You will most likely blow the core apart rendering it useless.
Most vehicle radiator systems maximum pressure is 14psi. Your home system is at least 45psi on a well or city water systems tend to be about 80psi.


e

You beat me to it..... AGREE 100% I have used air to clear the blockage but you do risk blowing the heater core apart but it worked fine for me on 3 vehicles

 

[jsthnt@gmail.com]

I flushed the heater today. We had a good weather day. It was 65 degrees today. I have some heat now.
Thanks for the help.

 

[Tlauden]

Just my .02 cents here, if there was junk blocking your heater core then you might want to consider flushing the whole system, that probably means there is junk in your radiator also. And you might risk the chance of blocking your heater core back up. Plus clean coolant may give you better heat out of your heater

 

[treeguy]

"Depending on who installed the heater, it could be tied into the wrong passages on the motor, there's an old PS article concerning this. The top hose is plumped into the thermostat housing on the motor, not radiator side of the thermostat and the bottom plumbs into the water pump and you have to move the generator out of the way to open and close the petcock on it."

Bingo! I had the same problem when I first got my truck. Found that this was the problem. I think unless one was aware of the many ports available to run the hoses then just seeing the hoses connected to the engine would make you skip checking their positions.

 

[bguy193]

Just my .02 cents here, if there was junk blocking your heater core then you might want to consider flushing the whole system, that probably means there is junk in your radiator also. And you might risk the chance of blocking your heater core back up. Plus clean coolant may give you better heat out of your heater

I would have to agree.

 

[steelandcanvas]

Bjorn (Cranetruck) will usually chime in with the PS article that refers to the correct heater hose hook-up on the water pump. I tried looking for it but had no luck. Next time I see it, I will download it.

 

[cranetruck]

FWIW, here are the PS mag instructions....

 

[jsthnt@gmail.com]

The heater is in the cab. And there is one hose on the top coming out right above the alternator. And the other one goes to the back of the engine on the bottom. I flushed the radiator this summer, but there was a hole in the hose to the heater so it did not get flushed.