HappyTrails

96 XJ 4.0L and AW4 transmission. Internal radiator oil cooler.

Does the oil enter the top radiator fitting or the bottom fitting?

Thanks.

00t444e

It goes in the bottom and out the top.

lawsoncl

Correct. This is to prevent trapping air in the cooler. If you're looking at the FSM, some of the diagrams seem to be labelled backwards, particularly the one showing the aux cooler.

dave1123

AFAIK, most transmissions take fluid from the torque converter drain and send it to the cooler and the cooled fluid is returned to the pan. The "Hot" line is generally the one closest to the front of the transmission, although it's sometimes not obvious which is which. Most of the heat generated in automatic transmissions is from the converter.

EZEARL

The outlet (front) line on my '96's AW4 connects to the top of the radiator's trans cooler.

Seems I'm not the only one whose noticed this:
https://www.cherokeeforum.com/f2/aw4...rences-250407/

CobraMarty

Yeah but what does that line do inside the radiator?
IDK either. Maybe internally it goes straight down and fills from the bottom. Maybe it is only located 'higher' for packaging purposes. IDK, never pulled the end cap off a radiator to actually look and see.
Sometimes things are not how they look or seem.

EZEARL

GOOD point. But alas my old radiator doesn't reside here any longer so I can't check it out. I do know that Spectra part #'s are the same for all XJ's except for ones with the closed cooling system ( I checked '90,'95,'96,and 2000). So if there was/is an internal difference in OEM ones I've had no issues with my '96 hooked up to a Spectra one.

dave1123

There's a coil of tubing inside a piece of pipe inside the radiator tank. The pipe helps radiate the oil's heat to the coolant. It shouldn't get an air blockage because any air will be sent back it the trans pan.

EZEARL

Makes sense.

00t444e

I just checked my 97 to verify and the front outlet line goes in on the bottom port of the radiator I have my aftermarket cooler plumbed in after the radiator. They must have changed it for the 97 model, mine also came with the factory auxiliary cooler I am not sure if that is a factor or not.

dave1123

My thoughts on the aux cooler is it should be plumbed in before the radiator so it gets rid of some heat before it warms up the coolant. Just my opinion.

lawsoncl

That arrangement also lets the radiator help get the trans fluid up to operating temp when it's really cold out.

00t444e

If you have the cooler before the radiator when it's hot, you would be heating the transmission fluid up after its been cooled by the cooler. The hot tranny fluid going to the radiator first isn't a problem for the cooling system, it was designed that way.

EZEARL

Mine didn't come with a factory auxiliary cooler but the lines were plumbed just like yours. Thanks for checking and posting that. Also I checked with B&M before installing their aftermarket cooler and they recommended it be put in after the radiator cooler.