Quote Originally Posted by Don Shillady
I checked the B&M directions and they do specify the return line for the sensor. OF course that would hopefully be the cooler of the two lines so that reading is optimistic.

Don Shillady
Retired SCientist/teen rodder
Don, like you I don't have a huge bunch of space "under there".. the connections for the radiator : trans cooler are especially tight. My first choice was 90' ell male thread X 3/8" compression brass fittings. Never a second thought! My 3/8" tubing was anodized blue aluminum tubing. I fabbed the tubings to bring the connections to the side of the radiator where I could add some hoses to provide a flex joint. The tubing is clamped to the frame with some of the rubber coated clamps and screwed into the frame.

I've never had a failure with any compression fittings. Until the state of Mass outlawed it back in the 80's we used them on brake lines!
I wouldn't worry about using them.