ATF cooler thermostat

[processengr]

Hi All,
Winter in New England iis coming. In my daughters car, the small plate type ATF cooler mounted in front of condenser is presently plumbed in series after the primary cooler in the radiator. This proved to be a problem last winter, the transmission not heating up quickly or at all to lockup.

• I am looking at 3 choices;
• Re plumb and put cooler before primary.
• Install perma cool thermostat. This has a constant bypass of ~10% and a set point of 180F AFAIK.
• Bypass the auxiliary cooler for the winter.

Comments please!

[benebob]

A thermostat sounds like a bad idea as that would create a pump problem and fluid starvation problems I'd suspect, besides 180 degrees is too hot for tranny fluid anyways. Granted, too cold of fluid is just as bad as slightly too hot. I'm assuming you didn't put a gauge on it, if you did that would help quite a bit on determining how close you are. A parallel set up would allow for the radiator cooler to do its job and allow it to heat up the fluid as the engine warms. If it is a replacement radiator I'd do this. If it is an original 92-94 radiator I wouldn't as they have a screen in the cooler which can get clogged causing those pump/fluid starving problems. Best high tech advice I'd suggest would be a slice of cardboard in front of part or all of the cooler... It works on my Nighthawk oil cooler. Even have a slick cardboard set up that is painte black with strap ties to keep it in place.

[processengr]

Originally Posted by benebob

A thermostat sounds like a bad idea as that would create a pump problem and fluid starvation problems I'd suspect

Unlike an engine t'stat the permacool thermostat has 2 in/2 outs, it is in bypass mode until the bimetallic spring opens the valve to allow fluid through the cooler. I don't think there would be any restriction from it.

[benebob]

Originally Posted by processengr

Unlike an engine t'stat the permacool thermostat has 2 in/2 outs, it is in bypass mode until the bimetallic spring opens the valve to allow fluid through the cooler. I don't think there would be any restriction from it.

Okay so now I see what it is. Have never looked at one so needed more explanation. I still wouldn't do it as 180 degrees is too hot to start cooling the tranny at (from one who has a gauge in his pan and knows just how hot things stay once they get warm). If you could get a t-stat that opened at 130-140ish that might be a different story

[svxistentialist]

In your cold winter circumstances I would re-plumb the additional cooler in parallel. I would also probably leave it that way all year round. It will do a good job anyway, summer or winter.

Joe

[NiftySVX]

I have the same problem, but mine is plumbed before the radiator. I usually just put something in front of the cooler, otherwise it will go in and out of overdrive if it is cooler than about 50 outside. This causes a drastic decrease in fuel economy, and it is annoying. I was planning on doing it this weekend.

[genzzel]

Most, if not all trans fluids are tested and designed to run at 175 degrees. Of course failures increase with temp ie 195 degrees and you will loose trans at 50,000 instead of 100,000 miles. Here is a site of interest http://au.geocities.com/ozbrick850/at-mortality.html I have the thermostat you mention, but it is from BM racing and is for transmissions. Hope to have it in soon--kinda getting cold here in northern PA.

[Hocrest]

Originally Posted by genzzel

I have the thermostat you mention, but it is from BM racing and is for transmissions. Hope to have it in soon--kinda getting cold here in northern PA.

What temperature is it rated at?

[processengr]

FWIW Here is a link to the Perma-cool unit
http://www.perma-cool.com/Catalog/Cat_page14.html

[genzzel]

BM racing unit is the same 180degree

[benebob]

Subaru's recommended tranny temp 140-170. Once warm the SVX even while crusing on the highway tends to retain that heat in the tranny.

[NiftySVX]

I would be interested to know where the 140-170 figure came from. Usually, the manufacturers don't really specify, just that it should run "at about coolant temperature. This 140 to 170 number seems to be unrealistic considering the way the cooler works. But, engineers often provide unrealistic figures. I am going to get in on a thermostat.

[benebob]

Originally Posted by NiftySVX

I would be interested to know where the 140-170 figure came from. Usually, the manufacturers don't really specify, just that it should run "at about coolant temperature. This 140 to 170 number seems to be unrealistic considering the way the cooler works. But, engineers often provide unrealistic figures. I am going to get in on a thermostat.

The owners manual. You know that thing in the glove box you must've not read. I can only tell you from my experience living with a cooler and a gauge in my pan that this does not sound like a reasonable solution for year round. Might work in the winter just fine but you'll be cooking your tranny on that first 70 degree day on your 25 minute commute to work.

[NiftySVX]

I have read the owners manual, I was just sayin that I don't really think that is a realistic figure. It could be though, maybe someone with a pan-mounted temp gauge could chime in.

[processengr]

It would be nice to have a thermostat set for 165F...OTOH, the thermostat only affects the auxilary cooler. If it opened at 180F, that would allow coolant to go through the aux. cooler, having already gone through the primary radiator cooler. The return oil temp. would be lower than the 180F setpoint as the thermostat measures ATF temp. before the aux. cooler. If it removed 10F then you would be close to the ideal temp...