It was really difficult to combine all of the info I found on different forums, websites about this topic, so I wanted to share a few things that I learned in the process of repairing (rather than replacing) my oil cooler. I have a 2009 Mazda 5 Sport with 78k miles. The oil cooler started leaking (Black, older design) between the oil cooler and the oil filter housing, as is common for this FoMoCo design and has been detailed in this thread.
As discussed, the dealer will only replace the entire unit with the newer design (silver) unit. My Mazda dealer here quoted me $480 for the part and labor to swap it out. I replaced the gasket in about 4 hours (could be done faster had I had all of the needed info in one place already) and for $13 plus a quart of oil and 1 gallon of engine coolant.
I ordered an oil cooler replacement gasket part at Amazon for $13.02 (this is the replacement gasket for the older black Oil cooler design)
https://www.amazon.com/dp/ (commissions earned)
There is a set of service manuals circulating online that was apparently leaked from a 2005 draft service manual, and is helpful, but not entirely correct for newer Mazda 5's since they switched at some point from the screw-on filter to the cartridge filter design, and the service manual is for the screw-on filter design. That is located here:
http://www.mediafire.com/file/wgev1ww9dc1c27g/Mazda5_WM.zip
It is worth looking at, but not exactly correct for newer Mazda 5 Models.
For re-assembling the oil cooler after installing the new gasket, torquing the unit back together properly is supposedly very important. Here are the torque specifications I found for reassembling the oil cooler: 25.1-29.5 ft lbs.
When re-attaching the unit I also never was able to find the torque specifications for re-torquing the unit to the Engine block, but found that it's important not to tighten too much or to get anything in the screw holes when re-attaching the unit. This is all I've found on that matter, but apparently got mine assembled sufficiently because it hasn't leaked in a month since doing it.
https://www.mazdas247.com/forum/sho...rque-values-for-oil-cooler-gasket-replacement
Additionally, there is a series of 3 YouTube videos where a guy actually
repairs the gasket himself. These were actually quite helpful (although assumed a lot of technical knowledge I didn't have!) - Note about those videos, I did NOT install the gasket solution he recommended between the engine block and the oil cooler (nor did I on the old gasket, since I replaced the old gasket with the $13 Amazon one rather than repairing it.)
Video 1:
https://www.youtube.com/watch?v=s3Yx3rFnMuc&list=PLMLlmUSfWO5-EdidQ9LI1ZMG4gkEeqrrx
Video 2:
https://www.youtube.com/watch?v=glhk_RQTH8k
Video 3:
https://www.youtube.com/watch?v=YO9mgpotcik
Disconnecting the Oil Sending Unit was a BEAR! I had to rotate the unit to get to the back of it to remove the clip, and wouldn't have known to do that except I found this detailed writeup on replacing the oil sending unit (see pp. 7-8 of this PDF) which helped me to figure out how to get it detached.
https://cdn.shopify.com/s/files/1/0420/1017/files/DM_Oil_Pressure_Sensor_Adapter.pdf
A couple of more points: it is not needed to drain the entire oil pan before doing this install. Just drain only the oil filter oil through the bottom of the oil filter housing and then you will have less waste and only need to replace about 1 quart of oil instead of all of it. I drained only the oil filter housing and was fine. I only lost 3/4 quart of oil in the install.
Secondly: You should probably play it safe and drain all of the coolant from the radiator. I did not, and had quite a mess. I instead plugged the two coolant hoses when I disconnected them from the oil cooler. But I still lost nearly a gallon of coolant in the process, and if I had it to do again would have just drained the entire system first. I plugged the hoses with rubber bands and cellophane, but it wasn't a pretty solution!
Hope that is helpful to someone. It wasn't easy, but was really satisfying to see it work and have saved over $400. ($100/hour for my time; I guess that was worth it).