Hi, I have a 1994 F-250 460 with a small coolant leak. It's from the upper radiator tank, drivers side, where an old line enters. The line is not in use anymore due to a new tranny cooler. The leak seems to be coming from behind the washer. My mechanic tightened it but doesn't want to tighten it any more because it might crack the tank. The leak doesn't amount to a lot of coolant but I want to fix it.
What are my options to repair it? I was thinking of draining the coolant to below the fitting, disassembling it and using something like jb weld or a high temp rtv sealant to seal it, and then put it back together.
Here's some pics.
Thanks, Jeff

 

Radiator repair shop.
I think there's a rubber washer on the inside and outside of the cooler.

 

A bad o ring should be easy enough to fix. Any other tips, hints, or tricks before I start to take it apart?

 

Let us know how that fix goes?

 

Permatex black RTV did the trick. I just loosened the nut, smeared it on the washer and tightened it up. No more leaks.

 

Why are you bypassing the in tank cooler? Fluid/fluid coolers work so much better than air/fluid. Plus, the in tank cooler actually WARMS trans fluid to operating temp in cold weather/low power situations.

 

My mechanic said this is better cause the coolant is actually hotter than you want the trans fluid to be. The original way didn't work too good on the old tranny. It overheated and died hauling my camper over a mountain pass. That was a fun night...

 

Your mechanic fed you a line. Aux trans coolers should be plumbed into the rad cooler feed line, out of the aux cooler into the rad cooler, then back to trans. You do it this way to prevent a hot trans from overheating engine coolant. Almost 1/2 of an auto equipped vehicle's cooling system load is the transmission. At least that is how it was told to me years back when I worked at a radiator shop.

 

Your mechanic sort-of fed you a line too. There is no way an overheated trans could put enough heat in that little bitty heat transfer strip inside a radiator to overheat an engine unless the engine was right on the edge of overheating anyway.
The aux cooler to rad and back to trans is the normal way to plumb in a cooler for normally COLD climates, like the northern part of the U.S.
Rad to aux cooler back to trans is the normal way for WARMER climates, and the way 90% of them are plumbed, even from the factory.
You are right that they need both.

 

I had the exact same problem on my truck a few weeks ago. I used Permatex on it as well. I think there is supposed to be a rubber seal. The new radiator did not have it.

I agree with the others comments about connecting as it was stock.

I thought that having the trans lines connected to the radiator was also supposed to help the trans stay warm in cold weather.

 

Yep, there is a rubber washer on the inside of the tank. Pulling on the line snugs it up. I didn't see a reasonable way of replacing the washer without a production.