When Mazda did a facelift update on the Mazda3 in 2007, they added an engine oil cooler to the European version due to high engine oil temperatures from high speed driving in Europe. High oil temperatures causes it to break down and the deteriorated oil can lead to engine damage. It is likely that because of this, there were numerous engine problems in the pre-face lift version of the Mazda3 in Europe (and other hot climate countries). The Middle East and Mexico also received this oil cooler for the 2007-2009 Mazda3. The European/Mexican/Middle Eastern Mazda6 2.0L/2.3L always had an oil cooler but the US/Canada Mazda3/Mazda6 (except for MazdaSpeed3/MazdaSpeed6/2010 Mazda3 & CX-7 2.5L Manual) and general market Mazda5 did not come with engine oil coolers due to cost cutting efforts, a milder climate and perceived lower speed driving. Installation of this oil cooler will improve engine reliability and enhance oil life.

1. Raise vehicle and set it on jack stands
2. Remove engine under cover
3. Drain the oil and remove the oil filter (if you don't know how to do this, stop right here and have a professional do this installation for you!). Be sure to install a new drain plug crush washer.
4. Locate coolant drain cock at the bottom left corner of the radiator. Use a short flat blade screwdriver to loosen the drain cock to drain the engine coolant. (Mazda3 shown)
   
5. Disconnect the oil pressure switch installed on the oil filter housing and remove it using a 24mm deep socket
6. On 2003-2005 models unclip the coolant return hose attached to the dipstick tube and discard clip (it will not be reused). On 2006 and newer engines, unclip the coolant return hose attached to a bracket on the lower engine block. Unbolt this bracket also and discard the bracket with clip (it will not be reused).
7. Unclamp the lower end of the coolant return hose from the AT oil cooler and disconnect it. Careful! Trapped coolant may spill, so keep a bucket underneath it!
8. Remove the original oil filter mount with a 10mm socket and 3" extension. (Automatic transmission Mazda3 shown)
   
9. Follow the coolant return hose up to the thermostat housing and locate knock sensor connector. Unclip (but not disconnect) knock sensor connector and wiring from the intake manifold. Move the wires out of the way.
   
10. Unclamp the upper end of the same coolant return hose and remove it. This hose will no longer be used.
    
11. Use brake cleaner and a rag to clean any spilled oil on the engine block and the oil filter mount gasket area. (Automatic transmission Mazda3 shown)
    
12. Wet the oil cooler gasket with CONVENTIONAL motor oil
13. Align the protruding pin at the bottom of the oil cooler with alignment hole at the back of the oil filter mount. Failure to do this may result in oil leaks and/or oil starvation leading to engine damage!
14. Install LF9V-14-789 or 9XG0-64-877L bolt through the middle of the oil cooler to the oil filter mount and torque to 27.50 ft-lbs (or 37 N·m) (torque to 25.50 ft-lbs or 34.50 N·m when using 9XG0-64-877L bolt) with a 15mm socket as shown.
    
    
15. Install the shorter coolant hose (LFF7-15-53XA) to the straight nipple on the oil cooler. Align painted mark on top of the coolant hose to be perpendicular to the top of the oil cooler. The protective sleeve end of the hose is the end that goes to the oil cooler. The clamps that come with the new hose are already properly positioned, so just squeeze them to unlock them and clamp them into place.
16. Align new oil filter mount gasket and install the oil filter mount assembly to the engine block reusing the original 10mm bolts. The gasket will only go on one way. Torque the 10mm bolts to 18.50 ft-lbs (or 25 N·m) in a cross pattern sequence.
17. Clean the threads of the oil pressure switch but ensuring nothing gets into the switch itself.
18. Apply a small amount of silicone sealant to the oil pressure switch threads as shown. Ensure there is no sealant 1mm from the end of the threads.
    
19. Install oil pressure switch to the new oil filter mount using a 24mm deep socket. Torque to 11 ft lbs (or 15 N·m).
20. Connect the other end of the short coolant hose to the AT oil cooler. Follow the painted mark to align the hose straight. The clamps that come with the new hose are already properly positioned, so just squeeze them to unlock them and clamp them into place.
21. Install long coolant return hose to the thermostat housing. Align the hose with the top of the thermostat housing using the painted mark. The clamps that come with the new hose are already properly positioned, so just squeeze them to unlock them and clamp them into place.
22. Reinstall knock sensor wiring where they belong. Do NOT forget to do this or the wiring may get damaged!
23. Install the "J" shaped end of the coolant return hose to the remaining nipple (the one pointing downwards) on the oil cooler. The clamps that come with the new hose are already properly positioned, so just squeeze them to unlock them and clamp them into place.
24. Fill a new oil filter with some oil (if using spin on filter) and wet the oil filter gasket with some motor oil. Install oil filter. Reconnect the oil pressure switch.
25. Oil cooler installation is now complete. (Automatic transmission Mazda3 shown)
    
26. Refill the engine with 4.5 US quarts (4.3 litres) of oil
27. Tighten the coolant drain cock and refill coolant through the reservoir tank (on the right side of the engine bay) using 50% mix with distilled water (or straight with FL22; do NOT mix water with FL22!). Squeeze the lower radiator hose to purge any air bubbles if necessary.
28. Start engine and check for leaks.
29. Allow engine to warm up then run the engine at 2500 rpm for 5 minutes.
30. Run the engine at 3000rpm for 5 seconds. Repeat this four to five times.
31. Check coolant level and top off to the "FULL" mark if necessary. Reinstall coolant reservoir cap. Cap should "click" in place after the final turn. It may take some driving and a few days for the coolant level to settle. Check the coolant level for a few days and top off if necessary.
32. Shut off engine and reinstall engine under cover.
33. Remove jack stands and put vehicle back on the ground.