I turned my heater on in my truck last week and when it finally warmed up it was like I had a fog machine on inside my truck. It smelled a little like anti freeze, but it has had that smell for a while. It just started with the FOG. Is this the heater core???? How hard a job is it to replace in a 1979 F250 4WD?

 

Your symptoms indicate a bad heater core. I have no idea how hard it will be to replace it, but on something built 25 years ago, I would like to think there will be plenty of room to work and that this will make the job easier. How is the coolant level? If it slowly drops and there are no other known/obvious leaks then this is the final indicator of heater core failure.

 

I have suspected it was going bad. I have been smelling the anti freeze and losing the coolant. I guess I have been lucky, this is the first vehicle I have ever had one go out in.

 

There is an electrolysis problem that is becoming the new haunting of today's automobile. If electrolysis is occurring in the cooling system it can/will cause rapid failure of the radiator or heater core. Electrolysis causes a chemical reaction that involves an ion exchange between the radiator or heater core and engine coolant. To state it simply, the coolant just eats the metal of the radiator or heater until there is none left. There are a couple forms of electrolysis that can occur in the cooling system. The most common is due to bad/acidic anti-freeze, which most people have a basic understanding of. The not so common electrolysis, but more deadly, is an electrically induced electrolysis. This is where the vehicle's electrical system causes a high rate of ion exchange in the cooling system that rips through heater cores or radiators. To test for this condition you need a digital volt meter. Start the engine and bring it up to about 2000 RPM. With the cooling system at operating temperature and the coolant flowing, connect the negative probe of the volt meter to the negative terminal of the battery. Place the positive probe in the coolant at the radiator and monitor the voltage. If you see .4 volts or greater reading on the voltage meter the coolant has to be flushed or there is a ground problem on the vehicle. If it is a ground problem you will most likely see the voltage reading climb if you turn on electrical accessories. To correct this condition will require inspection of the vehicle chassis/body and engine grounds. You may have to install a ground wire on the heater core and/or radiator to the battery. Electrically induced electrolysis in a cooling system is a mean beast. But it can be easily tamed with diagnosis and a good ground wire. This may be the reason your heatercore has failed. And as far as the difficulity
level on the replacement is is pretty strait forward. But can be
a little overwhelming to a novis. Most heatercores only pay about
100$ to replace find someone you trust & pay them to do it.
turbo ted.

 

You give me a lot to think about, thanks for the input. I have the heater core out, just waiting on the new parts to come in so I can get it back on the road. I am replacing the evaporator core and blower motor while I have it all apart. I will also be replacing the a/c hoses, dryer, condensor, orifice tube. I am trying to get the a/c working, not sure about the compressor yet. Any other suggestions as to any other parts that may need to be replaced while I have everything out under the dash?

 

I am not a 79 expert, but check your vacuum lines that operate the blend door or climate controls. If they crack, your manifold vacuum is screwed, and the air won't work correctly.