Hi all! I haven't posted anything in several months since I haven't been working on the trucks. However, today I decided it was time to replace the leaky radiator in my '93 GMC S15 Jimmy. Everything was going fine until I got to the lower tranny cooler line coming from the bottom of the radiator. The fitting on the end of the line is so corroded into place that it didn't want to release. I put my flare nut wrench on it and only managed to round out the fitting. I tried locking pliers and couldn't get it to budge. Because this is the lower line I don't have a lot of clearance to get tools in there so it's a real pain in the ***.

I'm thinking the best thing to do is to cut the hard line and then replace the end of it that goes into the radiator. What's the best way to do that? My first thought is to cut the line in a nice straight section and then get some new hard line and a new fitting and then use a compression union to join them together but I don't know if a compression union is the best way to go. Will there be any problems with the union loosening up from vibration? I also have access to donor lines from my '94 Jimmy that I wrecked, but I don't want to completely replace the entire line if I can avoid it.

What's your opinion on the best way to fix this?

 

you can go the compression fitting route or replace it with rubber line and hose clamps. if you do the rubber line thing, try to flare the metal a bit so it has something to hold onto. i know they sell like 15 inch sections of pipe with fittings at autozone for fuel line repair. check out their help section and see if one of them looks like it will work for the trans line, they are similar size

 

I decided to go with the compression union idea. Since tranny fluid is low pressure that seemed line the easiest solution. Flaring the end of a tube while still in the truck seemed needlessly difficult as compared to the compression union idea. I went to AutoZone, grabbed a compression union, cut the end of a tranny cooler line off from my wrecked '94 Jimmy, and put it all together. Here's a couple pics of the solution:

<blockquote class="imgur-embed-pub" lang="en" data-id="a/glvjd"><a href="//imgur.com/a/glvjd">Compression union on transmission cooler</a></blockquote>

I haven't put the new radiator in yet so I haven't checked for leaks but I'll do that in the next couple days and report back.

 

A compression fitting will be fine as long as you installed it correctly,

As for low pressure use only hell back a 100 years ago in my oil patch days I've see them used is lines holding massive pressures with no problems.

Trans lines, brake lines, fuel lines , ect they make a good permeant patch

 

Well, as it turned out, this job was a major problem. AutoZone got me the wrong upper radiator hose twice. They also got me the wrong radiator once. Eventually they got me all the right parts. I put it all together today and it works great. I ended up having to abandon the compression union in favor of bubble flaring the end of each tube and putting transmission oil cooler hose in between. The hard line ended up being too short and I couldn't get it to line up to the radiator properly. Despite all of the problems I was able to get it all together and the truck runs once again.

After getting all the correct parts from AutoZone I talked to the manager who told me that the reason I got the wrong parts is because the original parts order was put in for a 1993 Chevy S-10 with a 4.3 TBI. Apparently in their computer system the Vortec wasn't an option on the Chevy S-10 for 1993. When he put my truck in properly all of the correct parts came up.

At least that job is over now.