Anyone know which direction the water pump pushes coolant into the heater core? Im asking because I bought a coolant heater (that plugs into AC) and has a directional arrow and I have no idea which route the coolant flows. While one would ASSUME it flows from the pump into the core and back into the block....I don't like to ***-U-ME.....LOL!

Thanks,
Al

 

Well, one might also assume that it flows through the block to pickup heat before heading to the heater core to make you warm, else you may get mediocre heat by pushing cooled coolant to the heater core.

That being said, I don't know it which way it actually runs on these trucks...also it's possible that it's different between I6 and V8?

 

Hot water comes out of the intake near the thermostat, through the heater core, and is returned to the water pump to cycle again. This is how EVERY engine ever made in a vehicle with a heater works. Hot water flows to the heater core from the intake or block near the thermostat... i.e. the OUT or HOT side of the system.

 

Yes, the hose going into the water pump would be the return from the heater. The heater supply hose would come from or near the thermostat location.
The engine heaters that go into a heater hose should be plumbed into the hose that goes to the water pump, with the arrow pointing at it, in most cases. Otherwise, the heater stays hot, while the engine isn't kept as warm, since the coolant would have lost most of the the heat by the time it got to the engine.

 

Could having the factory heater hooked up backwards keep the engine from reaching operating temp?

 

No. It doesn't matter which way the coolant flows through the factory heater core.

 

That's what I though. I guess my issue is caused by something else.

 

But I've been told that the input to the heater core should be the bottom of the core to keep sediment flushed out.

Now, if a vehicle doesn't come up to operating temp, how do you know? Can you trust that old inaccurate gauge? Do you go by the heater output and assume that the core isn't clogged? Hmmm.

 

Easy to tell. Both hoses to the heater core should be hot. If one them is not very hot, that means there is little to no flow through the heater core.

How do you tell if your thermostat is working? Start the engine cold in the morning with the radiator cap off. If you see flow through the radiator by looking down where the cap was, the thermostat is stuck open. You will also feel the upper radiator hose starting to get warm after just a few minutes of running the engine.

If the thermostat is working, you will see no water flow in the radiator with the cap off, and the upper radiator hose will remain cold till the thermostat suddenly opens.

 

If the engine is getting up to temp, but the heater isn't putting out good heat, there's a couple possibilities. A partly blocked heater core that does not allow for good coolant flow, or the hot/cold blend door isn't fully opening/closing. On a non A/C truck, the blend door is cable operated off the temp selector lever, and is located under the hood, on the top side of the heater box. Watch the lever on the door while someone moves the control. If the lever doesn't appear to move much, try manually pushing the lever towards the cable hold-down clamp.
If the truck has factory A/C, I beleive this door is located in the same general location, but is vacuum operated. It can also be moved by hand, and even wired in the needed position if need be.

 

Or (to add to Rouge_wullf's post above...) the seals inside the heater box are bad.

IE: I was driving home last week and a small chunk of the blend door seal came through my defroster vent, the heater was significantly cooler after that. I will have to figure something in the way of putting a new seal in mine etc...

 

My 1981 doesn't have AC, so replacing the heater core requires removing that entire black box (an ordeal by itself).

The cable-operated blend door at one time had foam rubber glued to it which sealed the door's edges to the box.

That foam was dried out and literally turned to dust when I touched it.

I cut a piece of 1/4" or 3/8" (or somewhere thereabouts) foam packing material from a computer monitor and used spray glue to attach it to the door (of course, only after first cleaning the old stuff off).

Also, used a tube of some sort of sealer goo between the box & firewall (to help the factory rubber gasket seal to it).

This seems to be working fairly well.

I don't think I took any pictures of this but I may have, will hafta go look & see if I can find any....

 

Yes , the line going to the waterpump would be coming from the HC. Imagine it as sucking the coolant through the HC. Also if you want to add a coolant filter at some time keep the direction of the flow in mind.

 

hello, long time ago you posted this but did you get an answer? I need the same help except I have no hoses and stating with all new so I have no markers like arrows etc. to go from...

 

Please see post #4 above for your answer:

"Yes, the hose going into the water pump would be the return from the heater. The heater supply hose would come from or near the thermostat location.
The engine heaters that go into a heater hose should be plumbed into the hose that goes to the water pump, with the arrow pointing at it, in most cases. Otherwise, the heater stays hot, while the engine isn't kept as warm, since the coolant would have lost most of the the heat by the time it got to the engine."