using Integrated transmission cooler as an oil cooler?

[ProdriveDreams]

So i just ordered a new radiator as mine is junk, and it occured to me that even the MT cars come with AT oil coolers... so i was wondering if anyone knows if you can just get a sandwich plate for the oil filter and run lines to the integrated cooler, if that would work for the heat exchanger. If i remember correctly the AT cooler is pressurized and should be able to handle engine oil pressures.

anyone with any thoughts or ideas speak up! i cant be hte first person to think of this.

[Huffer]

I know that in some years the AT and MT rads were different, so the thought never crossed my mind. You do want to check on the pressure levels for the AT cooler though.

I do think running an oil cooler AND/OR an additional AT cooler is a good move particularly if you race/track the car.

I had been toying with the idea of installing a small cooler for my oil using a Summit Racing kit.

[Reason]

I'm pretty sure the 1st and 2nd gen us a MT rad and AT rad.

[ProdriveDreams]

Well mine is an MT car with nipples in my radiator to hook up the AT, so obviously it varies, but either way im replacing it with an aftermarket because mine is shot and my new one does also have the nips. I checked the pressures and the tranny pumps at like 80PSI so i should be fine with the 30-50 PSI of the oil.

I looked around here legacy central, and nabisco and could find no evidence of anyone doing it before, which made me nervous like there was some obvious reason iw as missing asto why you couldnt do it. But since its almost time for an oil change ill jsut slap it ont here and if something catastrophic happens ill jsut keep my oil change tools plus oil and filter int he car so i can do road side repair.

wish me luck!

[Reason]

It could also mean your radiator was changed before you got the car (the possibility is there if you didn't buy the car new). Subaru DOES use a lot of same parts through out there whole line up. So they could have easily used a AT rad in your manual.

[Huffer]

So are you going to run a sandwich plate between the filter and the radiator/AT cooler?

This should be a good mod - hook us up with pics & a writeup!

[sharky nrk]

ok well here is counter point on this

not sure about Subaru specific setups but on Honda's (I am making the assumption that Subaru uses a similar setup) this is not well suited (read: does not mean it will not work) for a couple of reasons. The ports are generally too small to effectively move engine oil, the cooler itself has very limited capacity, and the desgin (a simple tube running through the bottom of the radiator) does not provide for much heat exchange.

its not like this is a smaller but extremely efficient heat exchanger on the bottom of radiator, it is not heavily finned like a radiator/intercooler (read: surface area necessary for heat exchange). It is similar to the power steering coolers found on vehicles, a simple tube running inside of the radiator at the front of the car to have air pass over it. The extra effort required to move the engine oil the extra distance through those small ports can strain the oil pump.

now I have heard of a few people that have run it like this and seen a 5-6 degree drop in oil temp on the track, and I have heard of people try and and starve a bearing on the next track session so its 6 of one half a dozen of the other. IMHO its simply not work the effort or danger of running this kinda setup, its not got enough capacity, flow, or efficiency to really make it worthwhile.

[Huffer]

Starving your oil bearings isn't going to happen if you ensure your oil level is increased by the amount of additional line and cooler capacity.

You do make a good point about the additional flow and whether or not the AT cooler can handle it - however, if the AT cooler can handle up to 80psi for ATF then oil shouldn't be a problem - providing the inlet and outlets are appropriate.

heat exchange-wise, without looking at the AT rad, I couldn't tell you if the AT cooler is simply a pipe running through the radiator, or if it is a complete section.

The fact that when you drain a Subaru AT of fluid, you only get 4qts from the transmission pan, tells me that there's 4+qts floating around in the lines between the cooler and the tranny. That's not an insignificant amount of fluid.

[MCarp22]

Using the trans cooler in the legacy would be stupid. The lines are too small for the volume of oil an engine needs. [/thread]


Starving your oil bearings isn't going to happen if you ensure your oil level is increased by the amount of additional line and cooler capacity.

You can add 50 gallons to the oil capacity, if none if it makes it to the engine because of the restrictive small oil cooler lines, well, you still end up with oil starvation.


tells me that there's 4+qts floating around in the lines between the cooler and the tranny. That's not an insignificant amount of fluid.

At least 2-1/2 of that is in the torque converter. The rest is in the valve body and center diffrential. I doubt the cooler and it's lines hold a pint.

[sharky nrk]

^^^ pretty much what I was going to say as a reply

[Huffer]

providing the inlet and outlets are appropriate.

[sharky nrk]

^^ noted