I'm beginning to think that a leaky Jeep is just a fact of life. The transmission cooler line on my '95 GC has had a leaky fitting at the radiator for almost as long as I've owned the vehicle. I seem to have leaks on both lines. I've read other people complain of this, and not wanting to spend $100+ from a dealer to replace everything from the radiator to the transmission. I agree. It sounds like the lower radiator fitting has a plastic clip that allows the hard line to mate to the rubber hose and in my case, this thing is what's leaking. The short section of rubber hose then has a screw fitting that connects near the front of the oil pan. If possible, I would like to replace that short section of hose, all the way up to the radiator itself, but I don't know what size fittings I need to look for. The upper line, has the steel hard line connected to the radiator housing and comes down past the lower junction and attaches with the same kind of plastic clip. That's my second leak. The other end of that rubber hose, does not have a screw fitting, but instead uses a crimp fitting to attach it back to hard line, making it more of a hassle to fix. But if I had to, I suppose I could cut the rubber hose a few inches past the plastic clip fitting and make a similar compression fitting.
I'd like to first take a look at the lower cooler line. At the radiator, there is a steel elbow that connects between the radiator core and the quick disconnect. Does that elbow screw onto or screw into the radiator core, and is this junction metal or plastic? I have a few feet of braided line that I got from summitracing a while back and I believe the external diameter is about the same as the rubber transmission lines. If it can handle the pressure requirements, I could use it, although I've no way to figure out the size of the connection at the radiator without taking it off and trying various fittings. I guess that goes for both ends.
I took the upper connection off to look at it. So, yeah. The hard line is flared and secured with a compression fitting, removed with a 19mm wrench. That fitting at the radiator is said to be a 3/8 NPT? I don't really NEED that connection to be redone, but if I end up having to cut the hard line and rework it, no harm in going all the way up to the radiator. I'm guessing the junction by the oil pan is the same sort of thing. I'm looking at the layout of some replacement radiators, and they show the lower connection with the elbow attached. On the factory radiator, will this fitting come off the radiator in the same way the top one does, or am I stuck with the elbow? It would be extremely handy to not be there.
It's the 4.0L. With both leaks, the problem seems to be caused by those quick-connects and I would really like to eliminate both of them. Most of the questions I had, I think I've figured out. The one question I have left is whether or not the metal elbow connection at the lower transmission line can be removed from the radiator or if it's something that I'm going to have to keep and work with.
First off do yourself a favor and make sure there is not a check ball valve on the bottom fitting at the radiator. This will clog up and burn up your tranz. Stick with the elbow/flare at the radiator. To redo the lines correctly it is expensive or you could take them to a shop that makes hydraulic hoses, they can fix them.
It took me a bit to figure out what to look for and understand why this would be a problem. I'm familiar with check balls inside the valve body, but wouldn't have thought about one inside a line. I did some further searching, finding it referenced as an anti-drainback valve, and there are some pretty disturbing descriptions of these going bad. I have experienced the feeling of a delay time between shifting into gear and the transmission engaging before, but it's been some time. When I first got my GC, it had a strange issue of locking out OD when it wasn't up to temperature. I fixed that by flushing the transmission and changing it's filter.
I see what you're saying about keeping the elbow at the lower radiator connection. It looks like that's a permanently fixed point that is not easily changed. I took the upper connection off to look at it, and it seems as though it's tapped for a 3/8" NPT and has a brass fitting screwed into it, converting it to the compression fitting. I have a -4 AN to hose fitting that I know is too small. For the heck of it, I'm going to pick up a -6 AN to hose elbow and see if it connects. When I replace the transfer case, and pull the transmission to replace all of the seals, I may decide to replace the cooler lines full run from radiator to transmission. Don't know yet, but if I do, that will be the time to do it.