I have a 1970 ford f 100 w/302 and 4spd. I had the radiator roded, the block flushed, new heater core w/blower motor. It blows hot air out of the vents, but it never really warms up unless sitting, and it's not blowing much air? Any suggestions on how to keep it warm inside? I'm in Idaho, and it usually isn't this cold, but at -9 in the morning, I need HEAT
Any suggestions would be great
thanks
Dustin

 

I'm battling similar problems with my truck, and I have found the following- The valve can stick and break the cable, leaving you with no flow through the core. These trucks use outside air only, they don't recirculate any of it, so it always has to fully heat the air. The air intake for the heater comes from the cowl area, which is a high pressure area when you are driving, forcing more air through than the core can heat. Also, in the winter, that great big three or four row radiator cools the water more than needed, not leaving much heat for the cab. Plus, the cowl likes to rust out between the heater box and wiper motor, letting cold air in. Any combination of these problems can cause an almost total loss of heat. To start with the easy stuff, put a piece of cardboard between the radiator and grill to reduce the airflow. On my truck, I am getting rid of the heater hose from the thermostat housing, instead I am going to run a pipe spaced about 3/8" off the exhaust manifold to pick up the core temperature. Also, run a 195 t-stat. Be sure to check the cowl area for any holes, it's easiest to do this during the day or in a well lit garage. Just get under the dash, and look for light coming in.

 

Also, these blower motors don't blow out a whole lot of volume of air anyway. Thats just the way they were

 

Dustin, I suspect your truck may be like mine. It is letting in too much cold air and over comes the heaters capacity.

John

 

Re the temperature, if your heater valve is working properly, I'm with BBBoy that a piece of cardboard in front of the radiator will work. You will have to try different sizes until you get one that's just right.

Re the air flow, one other common problem for these trucks is the cloth heater hoses under the dash. They are usually torn up so if you have it on defrost, most of the air flow is directed under the dash instead of onto the window.

Finally, make sure you have your hoses hooked up properly. The heater vlave should be on the outside hose, the one that goes to the intake manifold just behind the thermostat as shown in this photo.
jor

 

Yeah, I have way too much cold air coming in while going down the road, and that valve you talk about is stuck open, and is on the right hose. Any blower motors out there that will crank out more air?

 

are you running a thermostat? if not you need to. also ive ran into a air bubble in the cooling system before. clamped the hose that exits the engine into the radiator and let the force of the water push the bubble through. fixed the problem.

 

Yes, i am running a thermostat, a brand new stant 195. Just need to get more air coming out of those vents.

 

Check both side vents. If not sealed properly up alot of cold air can come in from these fresh air vents by your feet. Usually old Ford trucks like ours have dandy heaters.

 

I see you guys are bad as I am, too tight to spring for the valve, Visegrip twice a year works. If you haven't pulled the hose and looked, I recomend you verify the valve is open. It's just the thing I would overlook, and there are valves out there that work backwards. Make sure you don't have restricted fittings, rusted or collapsed. Stick a piece of clear hose in to check flow. Those infrared temp guns are slick to know what actual temp is going into the core.

Next slim possibility may be the blower wired backwards. If it is, it will put out like neutered.
Pull the vent piece that is screwed to the kick pannel, make sure that it's clear up to the cowl.
Is the heater core sealed in the box so air can't get around it? Also it doesn't take much of a hole in the firewall or torn boot to chill the cab.
Now that I'm done, since you said it heats sitting still the cardboard may be all you need, I wouldn't be supprised in those temps.

The heaters in any one of my trucks blew plenty of air and would cook me out. Of coarse it can be 55 and overcast any day of the year in Western Washington, but it does get cold.

 

Ok, to clear things up, that valve is stuck OPEN. When I had the radiator rodded, block flushed, and new hoses put on, the guy told me it was indeed stuck open. It gets hot, but dosen't keep the cab warm. I'm going to get out the duct tape and close up any open holes on the firewall, then seal the wing windows with permatex, then figure out how to get those blasted fresh air vents on the side to seal up. Mine leaks on the drivers side where the handle slides. How do I seal this up? The blower motor also is wired the right way, it blows, it just dosen't seem like enough.

 

> Mine leaks on the drivers side where the handle slides.

I removed the vent, slide it all the way shut (leaves had clogged it), stuffed foam into the back of it (maybe this was the pass. side?), then duct taped over the foam, then taped around the end of the vent to hold the other duct on, ran red RTV over anywhere it might leak, then around the complete edge of the vent, then installed it.

On mine, I removed the heater box assembly, and lubed all the pivots and doors to make sure they opened and closed all the way correctly (the draft doors where not working properly) and fixed some of the old foam that provided a seal.

Then I red RTVed around the heater core tubes on both sides of the firewall to seal off cold air from coming into the cab past the hoses.

 

Just trying to cover all bases while also helping anyone who might not have done all you have. Good luck.

I thought about mentioning an idea to block outside air at kick panel then opening the passenger vent to make the heater recirculate cab air. To do that maybe pull the screws at vent and slide a piece of cardboard in to cover hole and replace screws. Then open the vent or pull the acordian rubber out. Dumb idea?

 

If the truck never warms up unless it's sitting still, then it seems to me that your new thermostat isn't working properly. It's allowing coolant to run through the block constantly and not reaching full temperature. I've seen new thermostats that didn't work properly.

 

The thermostat is working fine, it's been replaced 2 times, and the third one I heated water up to right temp to see if it was opening, and it does open when it is supposed to. Having a hard time keeping the air in.