dnuccio

as some of you know, i recently fried the engine in my ZJ. i believe it happened because of the radiator i put in. on my build sheet, it lists NMCP Heavy Duty Engine Cooling. before i replaced the radiator and the rest of the cooling system, it NEVER ran hot. only reason i replaced it was because the tank was split and leaking. i replaced it with a spectra premium CU1394 from rock auto. i noticed now that it does not say "w/ HD cooling" for this radiator. i did not think to compare the 2 radiators before i installed it. im starting to think this was a standard duty radiator and it didnt have the cooling capacity for my jeep (i was towing a trailer in 105* weather when it overheated). this coupled with the fact that while towing, the trans worked harder, got hotter, and transfered that heat into the engine coolant via the transmission cooler in the radiator, i think thats what did it in. when i get the engine put back together and a new radiator, i will be bypassing the radiator transmission cooler and adding a large external cooler for the transmission.

am i on the right track here?
found this radiator on quadratec, good? bad? yeah its expensive but if it will keep my jeep cool, ill go for it.
http://www.quadratec.com/products/51210_6213.htm

dave1123

If your ZJ has a factory tow package, you should already have an aux cooler. If you don't, by all means install one. I would not eliminate the rad cooler because it also WARMS the trans on cold days. I would, however , make sure the hot fluid goes to the aux cooler first, otherwise you will be heating up your radiator before you cool the fluid. Same as not having an aux cooler.

My brother found out the hard way. His Chevy truck blew the rad cooler so he plugged it off and installed an aux cooler. It worked fine until winter. Then the trans didn't want to shift until it warmed up, which was a LONG time. Most of the heat in a transmission is generated in the torque converter and then not until it's under load.

IDK about jeeps, but with Chevys, The standard radiator is a single row of cores, the HD is 2 rows, and the extra heavy duty for trailer tow and diesels is 3 rows. I've been told that a jeep with A/C has 2 rows.

dnuccio

I have the small factory external cooler. I am not worried about the trans not getting to temperature, because i live in Arizona.

I did some more research, and it turns out the radiator i installed was just a single row. that coupled with the trans heat in there probably killed this thing.

dave1123

Yeah, probably. If you're using the jeep basically on-road, you can add a long bar cooler under the bumper in addition to your factory cooler. That way, forward motion will add extra cooling and help your radiator do it's job. You might even install a large electric fan instead of the engine-driven fan for those times you sit in traffic. My 2000 WJ ONLY has an electric fan and it stays cool in all conditions. In your location, I would wire it to run constantly when the ignition is on.

Also, when towing, you should turn the O/D off. It will use a little more gas, but will help save transmission heat. I wish I had looked at your signature block before I rattled off about using the rad cooler. I know it get quite cold in the mountains at night, but I don't think you'll have a problem. I know I'm from NY, but I spent a month in Albuquerque, NM so I know what it's like where you live.