Now isn’t this an odd title for an article? Is the title insinuating that the transmission and the cooler line are competing with one another? I thought transmissions and cooler lines worked together in harmony. Well, I know at our shop, we have certain cooler lines that have drawn special attention in the past couple of years. We have been ‘clipped’ with some unexpected comebacks.
Few things slow down an R&R job like frozen cooler-line fittings. The metric cooler-line fittings used in Isuzu 4L30 applications and Toyota trucks with A340/30-40LE (see Figure 1) are frustrating enough to make you want to reach for the tubing cutter and start cutting rather than struggle with stubborn lines.
With their fingers crossed and the cooler-return line still in the bucket, they start the car up. The cooler line makes a little pop, a spit, some foamy fluid then, lo and behold, a nice clean steady stream of fluid comes out of the line. Mission accomplished. The converter has charge. After the cooler line is re-connected, the trans is topped off, road tested and everything works perfectly. End of story you say. Not quite yet. The question that remains is what did we do to correct whatever was wrong with the unit? We did not find anything to point a finger at as to the cause of the problem.