New water pump not pumping through auxiliary output

[mpierce9]

hello, I've been trying to trouble shoot a heater problem for some time now. The original water pump never pumped through the auxiliary output nipple so I replaced it. Now the new pump doesn't either.

What am i doing wrong?


Water pump clearly in the center of the image. The hose with the worm clamp is around the fitting that is not pumping. I've tested this by removing the hose from the firewall and watching while the truck is running. I have burped the system multiple times with no change.


Any insight is appreciated.

Water pumps strong through the rest of the cooling system. Truck stays at 180-190 degrees.

[ray_mcavoy]

That fitting on the top of the water pump is on the return side of the system.

Where is the other heater hose connected? It looks like there is a pipe plug in your intake manifold just to the rear of the alternator where the hose that feeds hot water to the heater core would normally be connected.

[mpierce9]

Originally Posted by ray_mcavoy

That fitting on the top of the water pump is on the return side of the system.

Where is the other heater hose connected?

Two heater hoses top goes to the water pump as seen here, the bottom goes to the radiator. Image below shows both hoses. Bottom hose is hidden in this image behind the funnel.

Originally Posted by ray_mcavoy

That fitting on the top of the water pump is on the return side of the system.

It looks like there is a pipe plug in your intake manifold just to the rear of the alternator where the hose that feeds hot water to the heater core would normally be connected.

I agree, I saw that plug there. But what is the connection to on top of my water pump for? Is it return or output to the heater core?

[ray_mcavoy]

Originally Posted by mpierce9

I agree, I saw that plug there. But what is the connection to on top of my water pump for? Is it return or output to the heater core?

Yes, that connection on your water pump is for the outlet of the heater core to return coolant to the engine.

The connection on the radiator is an alternative location for the heater core return.

So the way yours is setup now, you have both sides of the heater core connected to the return locations.

The smaller (5/8") heater hose should run from the heater core to the intake manifold (where the pipe plug is now).

The larger (3/4") heater hose should run to the return fitting on the radiator -OR- to the return on the top of the water pump.

[mpierce9]

Your insight here has been very appreciated. . . Now let me ask you this. That plug currently in the intake manifold, if I remove it, where would I get a threaded fitting to place in that newly opened hole in order to allow the heater hose to attach? Would it be reasonable to swap the plug and fitting currently on the water pump?

Is there an image or diagram somewhere of a water pump and its directional flow? I've googled with zero luck.

[ray_mcavoy]

Originally Posted by mpierce9

Your insight here has been very appreciated. . . Now let me ask you this. That plug currently in the intake manifold, if I remove it, where would I get a threaded fitting to place in that newly opened hole in order to allow the heater hose to attach? Would it be reasonable to swap the plug and fitting currently on the water pump?

You're welcome!

Yes, if I remember correctly, the intake manifold and water pump both have 1/2" NPT threads so you should be able to swap the pipe plug and hose nipple.

Originally Posted by mpierce9

Is there an image or diagram somewhere of a water pump and its directional flow? I've googled with zero luck.

I don't think I've ever seen anything like that online. But I think I have seen a diagram (or at least a very good description of the coolant flow) in some older service manuals.

[mpierce9]

Well this is resolved. . . You we're exactly right. I made the switch and routed the return hose directly to the radiator, and the input hose to the manifold nipple. I capped off the opening in the water pump with the block off plug that was originally in the manifold. Truck got hot in about 3 minutes. Truck got super warm in about 4-5 minutes. Thank you very much.

[ray_mcavoy]

You're welcome! Glad to hear your heater is working now