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Discussion Starter #1
Why does the coolant return elbow (return from the heater core, screwed into the intake manifold) have a dip tube on it? Will a plain elbow with no extension tube work as well, or is there a reason for the dip tube?
 

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The dip tube is to pick up water from the bottom of the water jacket. If there's air in the system, that's exactly where the air will be (top of the system), so the tube is designed to not suck the air, but water intstead.

Will one without the dip tube work just as well? Probably, but I've never tried it.
 

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Discussion Starter #3
The dip tube is to pick up water from the bottom of the water jacket. If there's air in the system, that's exactly where the air will be (top of the system), so the tube is designed to not suck the air, but water intstead.
I thought it was the return - doesn't the port on the water pump push coolant to the heater, and the manifold port is the return? If it's the other way 'round, I understand the dip tube.
 

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The top of the manifold is the supply TO the heater, the other side goes to the suction side of the pump .
That's why , if you loop the hose from the manifold to the pump (bypassing heater core), engine probably will run hot !
 

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Discussion Starter #6
Got it - thanks to both of you.

The punch line is that the original elbow (probably not original, but OEM) has no dip tube. I hadn't wanted to bust it off the old manifold, but I did out of curiosity. Not sure if it's a bad replacement, or if the tube was removed at some point, or corroded off. In any case, the heater was working fine for the last few years, so I don't think it's a big hairy deal.

I'm going to use a machined brass elbow, but now I will sweat in a dip tube to make sure it's working as Henry intended. :)
 

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I had to get a straight fitting to go on my airgap intake, and it works just fine. I am sure the dip tube serves it purpose, but I don't believe it is a necessity.
 

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Discussion Starter #8
I am sure the dip tube serves it purpose, but I don't believe it is a necessity.
Probably not - but I fabbed one up anyway.

For the record, the recipe was:
  • 1/2 pipe - 1/2 compression machined brass elbow
  • 3 inch 3/8 brass pipe nipple
  • Grind most of the compression fitting's threads off, leave just enough of a ripple for the coolant hose to grab
  • Press the nipple into the pipe fitting and sweat solder it into place
  • Measure the depth into the intake manifold and cut the nipple so that it's about a pipe diameter above the shortest point
  • Smooth edges, purty it up and install
Pics if anyone wants 'em.
 
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