What is the transmission oil cooler and where is it located? 

A transmission oil cooler helps keep your automatic transmission fluid from getting too hot.  The friction generated by the moving parts of the transmission cause the parts, and the fluid or oil, to heat up.  Some vehicles use a transmission oil cooler to cool off the fluid.  This is seen most often in vehicle’s whose transmissions are expected to work hard—like trucks and SUVs intended for towing. 

The fluid flows from the transmission oil pan through rubber or metal lines to the transmission oil cooler, which is essentially like a radiator.  Just like a radiator, the cooler has tubes that absorb heat from the fluid, and fins that dissipate the heat into the air.  The oil cooler is usually mounted behind the grille in front of the radiator. Transmission oil cooler lines run through the engine bar to connect to the oil cooler, which is usually mounted behind the grille in front of the radiator.

How do I know if my ­­­­ transmission oil cooler needs to be replaced?        

Like a radiator, a transmission oil cooler can become clogged or develop leaks.  Either clogs or leaks will make the oil cooler less effective at cooling the transmission fluid.  As you might expect, the biggest problem that oil cooler lines face is leaking. The lines can leak oil, which reduces the overall functioning of the oil cooling system. This puts strain on the transmission.  The transmission might slip during gear shifts or might change gears abruptly.  Shifts might occur at odd times, either too early or too late.  If you change the transmission fluid, you might find that there’s an unusual amount of sludge or debris in the fluid. 

If oil is leaking onto hot parts under the hood, you may see black smoke rising from under the hood.  Leaking oil can also get into the engine, causing it to run poorly and emit black smoke out of the exhaust.  The best way to identify leaks is by visually inspecting the cooler. 

Can I replace the transmission oil cooler myself?  

Many do-it-yourselfers are intimidated by the idea of working on their transmissions.  We don’t blame them; transmissions are complicated.  Replacing the transmission cooler, though, is one transmission job that a driveway mechanic can complete.  Removing your grille should help you access the oil cooler.  You’ll want to have a catch pan ready before you disconnect the oil cooler lines.  Disconnect the lines using a line wrench.  Some oil will drain out.  If you're replacing the lines, then you can pull them out out. Manuevering the lines through the engine bay might be the most challenging part of the job, particularly if you have metal lines. At this point, you can unbolt the cooler from the radiator support.  Install the new one and connect the hoses.  You will need to add transmission fluid to replace what was lost during the repair.