I have 1999 4.0 with a leak at the fitting that threads into the radiator. Is Teflon tape an option? It looks like it is just leaking right at the fitting.
I've looked at a ton if threads, it seems most people have trouble with the rubber part but I think my only leak is at that fitting.

 

Said it before and I'll say it again...

If the leak is bad enough, it isn't worth dealing with these fittings either on the rad or back down the line a bit at the quick disconnects.

Just cut the lines and run them straight up to a B&M trans cooler in front of the radiator, however you want to mount it (~$60, Amazon) and run hose clamps.

It sounds like work and money, but having to deal with those lines is worth the $60 for the "upgrade". Done it on 2 XJ's already.

As an added bonus, the trans lines will then be out of the way if you ever need to drop the pan.

 

With the Factory tranny cooler bypassed, what tranny fluid temps do u see?

 

There has been discussion on other forums about the trans fluid running too cool/cold at start-up in real cold weather, with just the separate cooler.
Some folks run them in series with the cooler in the radiator, like down-stream from the radiator cooler.

On another note, buying new cooler lines to go to the radiator is likely not cheap either...(?)

Just some observations.....

 

Appreciate that, I'm sure I'll have to do that eventually but I have about a dozen other little things to fix too. Going to start with some thread sealant and go from there.

 

That's the way the Factory runs their optional auxiliary tranny cooler and that's the way the instructions that came with our auxiliary tranny cooler said to install the auxiliary cooler. Forums r full of opinions.

 

That's just one option, running it with the factory cooler, but it defeats the purpose of killing 2 birds with 1 stone and eliminating the connections at the factory radiators.

Running a new B&M by itself is still going to for sure be cooler even by itself than the stock trans cooler anyway, and even if not owell, it stays cool enough either way, myself and a few friends I know just do this to eliminate the "quick" disconnects and radiator connections.

 

Really? We run a B&M #70264 auxiliary cooler and the instructions that come with the cooler say run it in-line with and after the OE factory cooler.

Eliminating the Factory cooler and not using a tranny fluid temp gauge to verify all is good, is a gamble. Do u and your friends run tranny temp gauges and know tranny fluid temps r with-in specs?

 

I don't have a tranny temp gauge, it's a renix with no gauges except for MPH. I don't know about my friends'.

If you google and research it a bit, it's known that you can either run it with the factory trans cooler or not, and also in any orientation you want (sideways, upside down, rightside up, etc) since it's not a straight shot from the in/out, it has to go up and through it anyway.

I looked into this quite extensively.

 

A gauge provides solid data to safely prove what works, what doesn't when doing mods. Good data always trumps opinion.......even a lot of opinions.

 

In my experience replacing the lines didnt fix the leak. Actually created a new one. My bottom line had the "fix" bypassing the QD but causing a leak. Switched out both lines since I was in there anyway. New line fixed bottom leak but top started leaking. Tried to reposition the new line (with flange opening) about a thousand times and even exchanged the new line for another and tried again. Kept leaking until we hit subzero temps here. Just my two cents. Also, teflon products were warned against due to possible contamination issues

 

I think the fitting was just loose, thread seal and a little Ultra Black did the trick.

 

Thats good to hear . I opted to replace the lines with a new set from Dormon 624-306. http://shop.advanceautoparts.com/p/d...306/15230048-P


when removing the front line from the trany the brass fitting broke off flush with the trany . Ace hardware had the 3/8 fitting that broke off. an had to use a extractor to remove it . I had to keep grinding down the tip to stop it from bottoming out inside the trany. what i thought would be a simple an fast job turned into a nightmare. Wont do that again

 

Thanks I'm hoping the lines last for a while longer, I got bigger fish to fry!
My next project is ofa o-rings this weekend.