Dear Fellow Brickboarders,

Hope you're well. I've always wanted to look at the in-radiator Automatic Transmission Fluid (ATF) cooler. I just retired a 12-year-old Nissens radiator (made in Denmark, in January 2003; installed in March, 2005).

The ATF cooler - which shows no signs of corrosion - is a double-wall copper tube, 1.25" (32mm) in outer diameter and about 12.5" (31 cm) long. At each end, a copper fitting is brazed to outer wall of the tube. The cooler weighs about 18 ounces (500 grammes).

At one end of each copper fitting is a 3/16" (4mm)-thick copper washer - one side of which is coated with a black sealant - and at the other end of each fitting is a nipple ending in a flare fitting. To those flare fittings are attached the steel ATF fluid pipes.

A 22mm (7/8") brass hex nut tightly holds each of the cooler's copper washers against the inner wall of the radiator's black plastic side-tank. The nipples with flare fittings protrude through the side-tank's wall.

Key point: loosening the hex nuts will cause a coolant leak, but won't allow any mixing of ATF and coolant. To cure the coolant leak, simply tighten the brass hex nut.

When loosening the 15 mm steel fittings - that secure the ATF tubes to the ATF cooler's nipples - it is required to use a wrench to keep from turning (loosening) the 22mm brass hex nuts. Should the hex nuts be slightly loosened, simply tighten them to snug.

Failing to use a wrench to keep from turning the brass 22mm hex nuts, though, will not damage the ATF cooler, unless: (a) the 15mm steel ATF tube fittings are corrosion-bonded to the cooler's nipples and (b) the corrosion-bonded fitting is turned with such force or so far, that the nipple is torn from the ATF cooler tube's wall.

Sven the Torquer (the Volvo worker, who tightened the transmission pan fill tube hex nuts) could surely apply enough force to tear the nipple from the ATF cooler's tubular body. Most of us could not do this without a breaker bar.

In short, the in-rad ATF cooler is very robust and is unlikely to become a source of water in ATF.

Hope this helps.

Yours faithfully,

Spook