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2004 Outback H6 Sedan, 1996 Legacy Outback H4
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Discussion Starter #1
I am going to be putting on a B&M Supercooler in my 04 H6 OBS sometime this week, and I was looking to find out which hose going into the radiator was the inlet and which is the outlet.

I want to be sure to put the cooler AFTER the radiator, but from taking a quick look under the hood, I could not figure out which one was which.
 

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2012 Outback 3.6R
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511 Posts
This is from a Subaru Outback service manual. Hope it will help.
atf linesOlder Subaru.jpg
Make sure your transmission looks like the one in the picture.
A sure but messy way is to open the cooler line and start the engine. Just be ready to catch a quart of oil.
 

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2004 Outback H6 Sedan, 1996 Legacy Outback H4
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619 Posts
Discussion Starter #3
Okay, so the top one is the return, thats what I thought, but wanted to make sure.

As for running it open, that is what I really wanted to avoid, but if it came down to it, that was my final option.

Thanks!
 

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2002 Outback Station Wagon & 2017 Volt
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20 Posts
If you can find a safe spot to grab both lines, have someone start the engine cold and the first one to heat up is the inlet. It doesn't take very long to get warm.
 

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'05 2.5i H4 4-Speed Auto w/Sportshift
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514 Posts
BMike is right, that is exactly how I confirmed which line was "out" on my AT Filter located inside my left fender. I started the car, in park, and felt the hoses.

One hose - the one going TO the filter warmed up first, then the other hose coming FROM the filter warmed up about five to ten seconds later.

I would think the TO and FROM at the cooler would be either the same or more of a difference in piping temperatures/times, in seconds.
 

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01 VDC, 05 R Sedan, 06 BAJA EJ257
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15,125 Posts
Think gravity. The return line will always be the uppermost connection on any type vehicle where fluid is circulated outside the mechanism for cooling. This is done purposely in the event fluid levels drop the systems can still pull a supply from the bottom.
 

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The return line will always be the uppermost connection on any type vehicle where fluid is circulated outside the mechanism for cooling.
Unless I misunderstand this, I'm not sure the return line is always uppermost. Think of the cooling system. The radiator, through which coolant is circulated, is outside the engine ("the mechanism"); nevertheless, the return line (coolant going back to the engine) is at the bottom, as it is on virtually all cars.

If we look at the transmission cooling lines in the diagram in post #7 above, we see that the outlet from the transmission to the cooler is just above the filter, and the return to the transmission is at the rear at almost the same level.

The flow through the ATF cooler lines is push, not pull. There's nothing on the return side to pull fluid back to the transmission. This is easily verified. Disconnect the cooler lines. Direct the outgoing line (to the cooler) to an empty container. Connect a hose to the return line and place the end of the hose in another container full of fresh ATF. Start the engine. The empty container will fill up as fluid is pumped out of the transmission, but no fluid will be drawn back in from the full container on the return side. This is a method often attempted to replace all the ATF, but it doesn't work because the transmission will pump out but not back in.
 

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'00 Legacy OBW Ltd
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306 Posts
On my USDM 2000 Outback it is inlet on the driver's side (left) and outlet is on the passenger side (right). I did a 'flush' of the fluids recently and figured it out the hard way (disconnect, connect drain hose and start the car). Note, the OEM transmission cooler inside the radiator is horizontal inside the bottom.

My transmission cooler is waiting to be installed. I will be installing it after the OEM cooler as well.
 

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2004 Outback H6 Sedan, 1996 Legacy Outback H4
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619 Posts
Discussion Starter #9
eggroller: Yes, I found that out from downloading and carefully reading the 2003 service manual.

Instead of tapping in at the top of the metal lines, I will just replace the outlet hose completely with the new lines to the cooler, and I will be sure to document the process as best I can.
 

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'05 2.5i H4 4-Speed Auto w/Sportshift
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514 Posts
I agree with plain OM, when I changed out my AT fluid, I disconnected the OUT hose from the oil filter and ran that into a gallon jug. For the adding of new fluid, I had a funnel in the trans filler tube (dipstick tube) and just kept pouring in the same amount of half gallons that were coming out. It worked perfectly.
 

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I agree with plain OM, when I changed out my AT fluid, I disconnected the OUT hose from the oil filter and ran that into a gallon jug. For the adding of new fluid, I had a funnel in the trans filler tube (dipstick tube) and just kept pouring in the same amount of half gallons that were coming out. It worked perfectly.
I have used this method successfully on my Toyota and Lexus cars. Did you shift through the gears while you were pumping out old fluid?
 

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where are the transmission lines .... output and input on the transmission. Are the lines connected with a rubber hose and clamp? I ask this because I have a leak somewhere on my transmission ONLY when it is -30c ( cold ) but it is only at startups....
 
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