After flushing the core, re-packing the surrounding foam and cleaning out the maple seeds and leaves, my heater STILL blows warm at best. I've replaced the thermostat with a 190 deg one, too. Blower moter blows strong. Temp guage rides just under the middle of the normal range when hot.

I've got a feeling that my heater, if working properly, should cook me out in the relatively small cab on a 45 deg day, when actually it just barely makes it warm.

So is the inside of my core just scaled up so much that it's not passing much heat? Is that possible? It doesn't look like it's had a hard life, and it flows freely.

Is a new core the next step?

 

If memory serves me right, there should be a heater hose shutoff in the engine compartment. Check the hoses near the firewall for a valve that has a lever where a cable would normally hook up. The cable may be broken or not connected to this. If you do have one you can replace it with a 5/8" plastic union for troubleshooting. The 5/8" union will be a $2.00 well spent in comparison to a new heater core that wasn't the problem.

 

Mine does. I suspect the core is clogged still, or as mentioned, the valve is not opening all the way

 

I've got brand new hoses running from the water pump to the heater core. I installed a big manual gate valve, and it's wide open.


So that's it, right? If the coolant is flowing freely to the core, It HAS to be the core, assuming the engine is up to proper temp, right?

 

Are the lines to the heater hot?Check you coolant level.Take off the cap when it is cold and leave it off untill the motor comes up to temp and see where the level is.If you have an anti freeze recovery system top off radiator and fill reseviuor to the corect level.If you have an open system fill to within a couple of inches of the top of the radiator.Best of luck.
Joe

 

Check both hoses when the truck is up to operating temp to see if you have flow thru the core. One will be slightly hotter than the other, but not much. If one is cold or slightly watrm, then you have a clog. if they're both cool, than you might have an impeller on the waterpump that's eaten away and not pumping, but I don't suspect that as your truck isn't overheating.
Another thing to check is the flapper doors are operating correctly. If you have one that's not closing correctly, you won't get good heat. The fresh air door may be letting in too much cold air or just not sealing correctly when it's closed. make sure all the cables are moving correctly and are hooked up. These have adjustments at the heater case where they connect. Disconnect one at a time and manually operate the doors. make sure they're not binding and open and close correctly. Move the dash lever to see if the cables move ok. Then put the lever in the off position and re attach the cables with the door in the correct position. You might just have a door that's out of wack and letting cold air in to keep the heated air from warming up enough.
I think you said you back flushed the core before? Pull the hoses off the engine ends and make sure the fittings in the block and waterpump are not plugged with crud. Flush the core again with water. Put the hose in one side, then the other to clear the crud.
A few suggestions to try............

Barry

 

Hey, Barry and others: thanks for the good checklist stuff.

I dropped the truck off at a garage this morning to have the cooling system flushed and filled. I checked it with a hydrometer(?), and it read good for 10 deg, NOT good enough for these climes.

So after I get it back I'll go thru the checklist, at least now the fluid LEVEL should be good (but I'll check it, anyway).
Thanks!

 

Welcome to getting older!!!!