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Discussion Starter · #1 ·
I'm looking to find out where everyone is installing their return line for the heater core. Should I attach it to the coolant inlet tube at the bottom right front of the engine? Thanks in advance for your replies.
 

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Hey, welcome to the forum BT!

I have one hose connected at top driver's side rear of head, and the other hose is connected at top passenger's side front of head. It works fairly well and supplies pretty good heat, if the engine would ever get hot enough! I think Paul in NY uses a different connection point and he says his really puts out the heat, so hopefully he'll post and clarify.
 

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The return line always needs to go to the suction side of the water pump for proper circulation (bottom rad hose connection or passenger side of the block between radiator connections). The connection going to the heater goes just before the thermostat on the head. So the flow circuit bypasses the thermostat and starts giving heat before the thermostat opens. Same proven set up as an early 89 - 93 Dodge Cummins. Use a shut off valve going to the inlet for Summertime, either a vacuum valve or a ball valve.
 

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The return line always needs to go to the suction side of the water pump for proper circulation (bottom rad hose connection or passenger side of the block between radiator connections). The connection going to the heater goes just before the thermostat on the head. So the flow circuit bypasses the thermostat and starts giving heat before the thermostat opens. Same proven set up as an early 89 - 93 Dodge Cummins. Use a shut off valve going to the inlet for Summertime, either a vacuum valve or a ball valve.
that's how i have mine setup.

There was a sensor on the inlet side of the water pump. i just took that out and put in a 1/2" npt (i think) fitting for my return hose.

no pictures, sorry.
 

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Thanks, Bob, that can be very confusing on flow inlet/outlet in relation to the shutoff valve. Yes, mine is plumbed just before the thermostat and yes, 1/2" NPY threads on both holes.

I had some clearance problems at rear of block as I wanted my engine weight as far to the rear as possible. There is a sender in the top rear driver's side of head which I removed, put in a tee and then attached hose to top of tee with a short nipple, and screwed sender back into the side outlet of tee. I think that's less than perfect as the sender does not have continuous flow past it and the exposure to hot water is much greater when water is circulating to heater core. Paul told me what that sender is for but I've forgotten now and it's not actively used on my install.

Somewhat related: there's an electric fan control thermistor/switch screwed into bottom water outlet passenger side of block on vehicles so equipped. I wired an auxiliary switch with lighted 'On' indicator to turn on electric fan as needed. On mine there were two threaded holes on bottom outlet so I was able to move sender from bottom to side, again for clearance. I rarely need the cooling fan, like never, even in the desert at high temps on long grades. Rush hour traffic might be a different story, but these things sure run cool.

Tip: you can mix pipe dope with anti-sieze compound for threads on vehicle water connections to aid in disassembly if necessary at a later time. Still seals very well and helps prevent corrosion.
 

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Hey, Paul the duck apparently migrated back...;)

San Juan Cumminstrano?
 

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Discussion Starter · #9 ·
Good info, thanks! I plumbed my heater hoses from the existing port on the head (right next to the thermostat housing). My return line goes to the radiator-to-engine return housing on the bottom passenger-side front of engine. We'll see this winter how it works, I like heat!
 
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