Can someone tell me which heater hose is the in-flow on the engine and which one is the out-flow?

 

Water flows into the engine through the bottom hose. Heat rises and that applies to hot water too. The thermostat is placed in the line, to ensure the water, (engine), temp rises to a desired operating temp before being sent into the radiator to be cooled.

 

That is good to know on the radiator flow. I am wondering more about the heater hose flow. Both heater hoses connect to the engine at the top of the engine, so I'm not sure which one is the out-flow and which one is the in-flow.

 

The line closest to the thermostat is usually the return line.

 

So, one of the heater hoses goes through a spacer under the carburetor. Are we thinking this is the out-flow from the engine and then it continues on to the heater?

 

the water pump suck . so the other hose pushes

 

I'm not familiar with that configuration. However, I would follow the lines. Does it exit the carb, then go to or near the thermostat housing? Or, you could trace back from the nearest line to the thermostat. That would be following the line backwards to the flow.

 

I don't think that anyone actually answered your question.

The heater hose outlet on the water pump is the pressure side and should connect to the lower inlet of the heater core, so that the air is pushed out the top of the heater core.

The heater hose connection on the block is the vacuum or return line. It flows through the spacer on the carb. The spacer on the carb is not to heat the carb, but to cool it to avoid vapor lock. The return line from the heater core is theoretically cooler, so you use that line.

 

You are 100% incorrect. the water pump is the suction side, which is why the lower rad hose is in the water pump as well. As far as the heater core is concerned, it's just a coil, so doesn't matter which hose goes where. Top bottom, left right, all the same. Which engine do you have in your van?

 

The lower RADIATOR hose is on the suction side of the water pump. But guess what? There is a suction side on a water pump and a pressure side on a water pump. The water pump sucks coolant from the radiator and pushes the coolant through the engine. Or you can say that the suction side of the pump creates a vacuum in the engine that draws the coolant through the engine. Suction, pressure. You can't have one without the other. The HEATER hose outlet is on the pressure side of the water pump, not the suction side. Coolant to the heater core flows out the water pump, through the heater core and returns back to the connection in the block which, by the way, is under suction, or negative pressure, as created by the water pump.

And you can hook your heater hose to whichever heater core connection that you want. But the factory used the lower connection as the inlet and the upper connection as the outlet so that water flowing into the heater core pushes the air up (which is the direction that it wants to go anyway, air being lighter than water) and out the outlet. Will the air leave eventually no matter which hose gets hooked to which connection? Probably yes. But he asked for the correct way to connect the heater hoses, so I told him.

 

i have had many many vehicles come into the shop with a complaint of "gurgling" after someone changed heater core.
with the customer standing there waiting and watching, i would grab two hose clamps, and a nut driver or pair of pliars depending on what was used to put the hoses on the heater core bibs. . clamp the two hoses, loosen the retainers, switch the two hoses, tighten the retainers ,and pop the clamps loose to let flow resume.
then tell them "fixed"
a simple thing like hooking the heater inlet hose to the top of the core will trap air in the core causing a gurgling noise when coolant flows through the core.
reverse the lines and the coolant coming in the bottom of the core pushes all the air out.

 

Nice post but you are still wrong, the water pump is still the return line for the heater, I owned a radiator shop on the Cape for 20 years, I know a little bit about heaters and water pumps. As for the direction of flow threw the heater, there are very few cars that care. As someone else mentioned you can get gurgling on some cars but not too often. Some cars have a 3/4 hose on the return line, and a 5/8 on the pressure side so you can't switch those, but if both hoses are the same size it wont matter unless you have a noise issue.
Eric

 

The only explanation I ever heard (I don't know if it's actually true) that made sense, is that the shutoff valve should be located prior to the inlet of the heater core, not the outlet. This (supposedly) keeps pressure off the core in the summertime or when not in use or somesuch thus extending its life. Hm.

 

Having the shutoff valve on the inlet side also leaves you with a cold core. if the valve is on the outlet hose, you will get radiant heat in the core.

 

In theory you're right, and since you have a choice it's a good idea, but once the valve is shut the air flowing threw the core will cool the core pretty quickly so it shouldn't make a difference as far as temp is concerned. Keeping the pressure out of the core is probably a good idea though.