[Vanube]

1985 Dodge B150 with a 318.

I noticed that there is not a heater valve? AKA the two small rubber hoses going to and from the water pump and the heater core are uninterrupted. Is there supposed to be a heater valve on one of those lines? Is that why it may not be coming up to running temperature? Dropped a new thermostat in with no change. Thanks!

 

[AllanC]

. . . .I noticed that there is not a heater valve? AKA the two small rubber hoses going to and from the water pump and the heater core are uninterrupted. Is there supposed to be a heater valve on one of those lines? Is that why it may not be coming up to running temperature? Dropped a new thermostat in with no change. . . . .

There should be one heater hose that connects near the thermostat housing (topside of intake manifold) that carries hot coolant to the heater core inlet. The heater return hose would travel flrom the heater core outlet to the water pump. Has the heater core been bypassed by a previous owner because it was leaking?

If there is a heater hose from the top of the intake manifold to the heater core, then it is possible that the heater core is corroded and plugged and will not allow hot coolant to flow thorugh the device.

If a coolant flow shut off valve were installed in the heater plumbing circuit, it would be vacuum controlled and only closed when MAX A C / air conditioning was selected. Since you have no heater flow control valve that is not the cuase of the no heat.

 

[Vanube]

Thanks so much for the reply.

"There should be one heater hose that connects near the thermostat housing (topside of intake manifold) that carries hot coolant to the heater core inlet. The heater return hose would travel flrom the heater core outlet to the water pump."

^Yes, this is the way it is on my van. The heater core has not been bypassed. I had it replaced a while back and if I recall correctly - that's when temp problems started. Can air in the system cause this problem? That was probably a year ago.

Both hoses to and from the core get hot.

No AC in the van.

 

[68RT]

This is the heater control valve and is vacuum operated.

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[68RT]

Also, check air flow to insure it goes through the heater core and into the inside.

 

[valiant67]

Are you saying then engine is running cold or just the interior heat is not warm?
Almost always when an engine runs cold it is a thermostat problem. But if you think the issue is the heater core, loop the heater hose to bypass the heater core and see if the engine runs warmer.

 

[ImperialCrown]

Only the vehicles with A/C have the water valve to shut off the hot coolant for 'Max A/C' as stated. The 'Heater-only' vehicles just have straight 'to & from' heater core hoses.

Otherwise the heater core always has circulating coolant. The temperature control lever will blend the fresh air & heated air with an adjustable 'blend air' door.

 

[AHBGuru]

Air in the system does affect heater output. So does a bad water pump.

Check for coolant leaking from the weephole at the bottom of the pump. Also, check for play at the water pump snout - if you can wiggle the fan blade, replace both the water pump and the fan clutch. Get the larger bearing pump, and a thermostatic fan clutch. Remember that the fan clutch always faces down, until installed.

Thoroughly bleed the system. Fill and bleed with the radiator cap off, or try it with the cap on and bleed it with a hose pick or small screwdriver at the top radiator hose. Recheck and fill as necessary.

Also, make certain the fan shrouds are all in place.

 

[AllanC]

The attached image shows the heater control levers in the instrument panel. The top lever operates a cable that moves the blend air door. This controls the quantity of air directed through the heater core. The bottom lever when in the OFF position blocks any air from entering the plenum and heater core. Make sure both levers are connected to their respective cables at the instrument panel and in the heater plenum under the hood. If you move the levers from full left position to full right position you should hear the doors move in the heater plenum box under the hood. Maybe during heater core replacement one or both were left disconnected.