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2015 Forester CVT
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649 Posts
Discussion Starter #1
I'm going to install a Derale plate fin cooler and flow control thermostat on our '15 2.5i CVT for towing. However this is strictly a transmission related request.

The plan is to try to use existing hose to best advantage and, if practical, keep the thermostat close to the OEM cooler/warmer. If need be the thermostat can be located near the auxiliary cooler with minor nerdly sacrifice. The Derale thermostat recirculates fluid back to the OEM cooler/warmer below 180ºF, directing fluid to the plate cooler above 180ºF. I plan to use the thermostat on its bracket as a tie-down point wherever I can squeeze a hand and a screwdriver into.

I have a drawing (AT-06641) of the cooler/warmer with the coolant inlet in bold. I am more interested in the transmission fluid inlet and outlet to the cooler/warmer as that is where I will be connecting the new cooler lines.

Any tips or recommendations about doing this minor surgery would be appreciated. Since there is lots of room on the 2.5i in front of the radiator, it looks like there are options here but clever suggestions are most welcome.

Thanks in advance for saving me some confusion and maybe a scraped knuckle or two.

GD
 

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2015 Forester CVT
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649 Posts
Discussion Starter #3 (Edited by Moderator)
The most difficult part was getting the hoses off the heat exchanger. Since the nipples are aluminum, one needs to be careful. I routed one hose under the air filter box. To find out how much additional fluid you need just fill the cooler, drain and measure then calculate hose capacity by multiplying internal cross section area by length of hose. Hose diameter is important. I got mine a wee bit small which made it a PITA to get on the nipples. I also painted the thermal valve black for better heat radiation and appearance. Since this is a fairly low pressure system, you don't need to go racer boy on the hose clamps. I think that I removed the grille to make the whole thing easier. Also a good opportunity to clean the radiator, install after market horns and running lights.

End result is that heat exchanger functions as OEM and fin plate radiator seems to work.

GD
 

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Thanks much for your feedback on this. I'll be going to a dealership tomorrow to get some CVT fluid. I'll do some calculations beforehand for the hoses and perhaps I will bring the cooler with me and fill it up there to check. Will err on the side of caution and buy extra volume.
 

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2018 Forester XT Touring CVT
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Curious how you ended hooking this up. I just received my JDM Subaru tS trans cooler but there aren't any instructions. After going through a bunch of parts diagrams and some Russian site and their pics...I think I have it mapped out. The Ascent and the Outback have an almost identical setup (layout wise) which helped immensely. Found a site that I could get Japan and Euro parts diagrams and came up with this. Maybe someone on this thread with an external secondary cooler could verify the path.

Comparing chassis/VIN numbers of 2013 Japanese tS STI and 2016 Australian tS STI; I found that the early Japanese model had a single external radiator cooler ONLY. Whereas the tS STI in Australia had the setup I was trying to emulate here with the heater/cooler inline with the secondary cooler; like the US spec Ascent and Outbacks have.

Please let me know...thanks!
534176
 

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2018 Forester XT Touring CVT
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The above post is incorrect...this new one should be the correct way to route the hoses. Attaching a photo from the Russian website with colored overlays to match my revised chart. Everything appears to align now.


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