I have FINALLY sorted my car's overheating issues and I thought I would post the story for anyone who might run into this and be looking for a solution.

I started with a stock radiator and stock cooling system. I also made the mistake of assuming that if the factory gauge wasn't reading high that the car wasn't overheating. I found out this wasn't the case after ruining an engine.

Lesson one: The factory gauge doesn't read high until the car is way too hot. Second, it only reads water, and the oil temps can be very high also. So buy aftermarket water and oil temp gauges. Installing them required buying a sender block for the oil temp that mounts under the oil filiter (Racing Beat, I believe) and drilling out an already existing partial hole in the water pump housing to mount the water temp sender.

Lesson two: The water temp issue will only solve so much. I bought a huge Mazda Comp radiator and did the thermostat housing block-off and switched to water and water wetter and installed a big electric fan. (I did all this in stages.) All of this was fine, but it didn't fix it really at all. I would still do these things, (especially the radiator) but don't expect miracles.

Lesson three: The factory setup for ducting sucks. I blocked off all of the extra space around the radiator, including in front of the radiator where those factory plastic pieces are, and made an aluminum sheet that went from the top of the oil cooler to the bottom of the radiator. Then I made some big holes in the factory drip pan so that hot air coming off of the oil cooler would go under the radiator instead of right into it. I also made a straight piece that went from the middle of the air entry hole in the bumper cover to the top of the oil cooler. That way some air would go directly into the oil cooler instead of over it. I made the bottom of the drip pan hang down a bit in front to catch more air for the cooler as well. This helped a lot. Still not fixed, however. But I would do this again.

Lesson four: Get a second factory oil cooler!! This was the thing that finally fixed it. I bought one off of eBay for $50 that thankfully doesn't leak. I then followed a forum member's advice and got swivel T fittings and oil lines from Aeroquip. The second cooler mounted in front of the first one only flipped left to right. Then the T fittings went into the first cooler and allowed me to run lines to the second cooler. I ran the coolers in parallel, not series. So in to in, not out to in. I also added a new oil pressure regulator from Racing Beat that kept the oil pressure even higher than stock even after adding a second cooler.

Now it runs so cool that I'm going to have to put a working thermostat back in. (I'm using a gutted one now.) I also run Mobil 1. It takes about 7 quarts to fill it up.

89 ITS RX-7