Water pump flow direction (1 Viewer)

izzyandsue

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Have looked for a while but didnt find anything on this: what does each port on the water pump do, suction or pressure (in or out) of the pump? Looked for diagrams, FSM, etc but nothing on the 2F. The pump I have has the lower oil cooler port, which in my case is connected to the intake side of the heater control valve. Thanks!
 

73FJ40

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The basics are that the pump inlet is fed from the bottom of the radiator and discharges into the block.

Hot water from the block goes out through the thermostat back to the top of the radiator. Hot water also leaves the block through a fitting at the top rear of the head into a hose to feed the heater.

Water returns from the heater through a hose that connects to a fitting located in the middle of the lower radiator hose.

Regarding your oil cooler, you should be able to figure out the flow direction based upon where it's connected in the cooling system.
 

izzyandsue

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Thanks, but this what I am trying to figure out. The connections to my water pump are as the pic below:

fj43 waterpump connections.png



And the connections for the system are as below. I can see where the thermostat housing is only connected to the upper hose, not back to the pump. What I do not know is if the water connections to the heater are both "pump outlets" instead of outlet and inlet, and that could be why the heat is so puny.

If anyone know the directions of the two pump ports above, let me know. T and P below are thermostat housing and pump.

fj43 water diagram connections.png
 

73FJ40

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What month/year is your truck?

It appears you are repurposing your oil cooler connections for heater supply/return?

This is the arrangement for 76 - 80 FJ40 California spec., so I'd guess that the lower line is the supply and the upper line is the return.

1610647764805.png
 
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izzyandsue

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It is an 1981, do not know the month as it has an overseas tag on the engine bay. Yes, they plumbed the port from the pump that would go to the oil cooler, to the heater control valve. I am just trying to find out if that line is an "inlet" or "outlet", as they might have just deadhead the flow in the heater, removing or reducing flow.
So what is the directional flow of each of the two ports (besides lower hose which I know is an inlet) is what I am looking for.
Also, the thermostat housing does not have the bypass port, just one outlet to the upper radiator.
 

izzyandsue

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What month/year is your truck?

It appears you are repurposing your oil cooler connections for heater supply/return?

This is the arrangement for 76 - 80 FJ40 California spec., so I'd guess that the lower line is the supply and the upper line is the return.

View attachment 2553107
I am guessing from the diagram that the input to the oil cooler is the one on the right, "colder" water enters and leaves hot through the top? I am deducting that, 35 years as a mechanical engineering and instructors of fluid dynamics and I am confused. Then what I am doing today is sending "cooled" coolant to the heater. Does that make sense?
I could cap off that pump port and find the original heater input location on the block, heard it should be on the left side.
 

73FJ40

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I agree with your deduction that the "high pressure" outlet from the pump is the cooled water leaving the radiator.

The customary heater supply connection is off of the left side of the head, near the firewall:
1610656054372.png

The picture above illustrates the OEM stock plumbing.
The picture below shows a later model OEM fitting. Note that the pipe threads are 1/2" BSPT.

1610655027986.png



The picture below shows the OEM location for the heater supply valve, fed from the top with a hose connected to the fitting above, and shows a homemade return pipe which is a facsimile of the OEM pipe used to fit behind the distributor.
1610656374563.png


The picture below shows where the heater return line connects into the lower radiator hose through an OEM pipe connection.
1610655320129.png
 

izzyandsue

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Outstanding, thank you. I can now remove and plug that lower pump port, and feed the heater from the top, left side of the motor. Looks like there is a perfect spot right aft of the temp sending unit, a plug with a square head. Thank you. Update the flow directions below.

If the thermostat had a bypass port, it would go where the Heater Return is on mine below, and the direct to heater control would go to oil cooler. I may need a different thermostat housing. Just placed an order in Partsouq for a few things, missed this!

fj43 waterpump connections.png
 

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