Original owner here...
To save reading time read here, otherwise listen to the rest of my story... :-) How hard is it to replace the stock radiator -- original to a direct fit replacement?

It's been over six months since my '94 FD (popular equipment package) decided to dump it's cooling guts. I knew it had a slow leak for months, but I couldn't see a leak, so I just kept topping it off with water (an ounce to a few ounces) before I took it out for exercise on the back roads. Anyway, about 30 miles from home it kept dumping water out gallons p/mile but I had 3 full gallons of antifreeze mixture and plenty of gas stations to fill up on my way home. Needless to say, I was bit depressed and thought my baby might be dead so I let it sit for way too long. Today I decided to see what's up and filled it then and let it run (started instantly and ran amazingly smooth) until I started to hear hissing noises coming from the radiator right under the relay box, then came steam. So, this 52 year old with a bad back is wondering how bad this thing will be to replace. Yeah, I'm older, but I've done all sorts of repairs in the past and I've got just about every tool imaginable (x2), so it's not that I don't know what I'm doing for most things. Strangely enough, my rx7 hasn't needed anything but brakes, tires, plugs & wires, so I've been lucky for ~90k miles. Well, I lied. I screwed up changing antifreeze back when it was still under warranty and didn't know anything about air pockets back then. Took forever to get the coolant buzzer to go off when I changed it, but apparently an air pocket or several showed up a couple days later and I blew the engine. Mazda replaced it, thankyouverymuch. Btw, the engine crate said using synthetic oil would void warranty. I used Castrol Syntec back then. I also used Petit pre-mix. They scolded me for the under drive pulley. FYI, since then, I bought one of those cooling funnels that burps the air as you pour it in and I use traditional Castrol oil and no premix. ...So, how hard is it to replace the radiator?

 

Original to original is direct drop in. Original to aftermarket "drop in" can take a while.

I replaced the original rad on my 94 with a "drop in" Koyo Rad in the fall. It was anything but drop in despite what Koyo claims. I had to bend a couple of brackets and make some cuts before everything fit.

I had to bend the stock lower rad brackets down because they were too high to accept a thicker rad. I had to slightly bend a few fins on the side of the rad to get it to fit with the AC condenser mounts. I had to cut a few things too but I can't exactly remember what I cut. Even with all that, the Koyo rad still wouldn't fit 100% and was slightly off on one of the stock bolts at the top.

 

So, your swap was for a larger, thicker than stock radiator? I was hoping to keep things simple by installing one that fits exactly as stock, but with aluminum tanks instead of plastic ones from Mazda. I don't plan to race my car and it's pretty much stock to keep things simple, so I'm hoping to find an easy swap. Sure I might run it a little hard, but it's for short bursts, nothing crazy like I used to do in my younger years.
Thank you so much for your reply! We are praying for your Canadian neighbors up north. From what I've seen there is unbelievable damage from the fires. How devastating that must be. Some of the images I've seen remind me of an EF5 tornado that wiped most of Joplin, Missouri off the map.

 

I have a Ron Davis radiator and it is a plug and play drop in. Believe Ron Davis were the mazdaspeed radiator suppliers. They are pricey though (~$600) and are built to order (i.e. takes some time to get). I remember reading the Koyo's only need one of the upper brackets modified. Contact Banzai racing, who also sell the Koyo's.

 

I have a koyo and is was a direct replacement. No modifications required

 

I have a Koyo radiator as well. The Koyo is all aluminum, a bit thicker than stock and drops right in with the removal of one AC condenser bracket.






If you don't remove the bracket, the radiator will rest on it and it won't sit all the way down. The lower radiator brackets need to be bent just slightly as well. They have little malleable "arms" on them that hug the radiator on the bottom side. Just bend them a bit to hug the bigger end tank and that's it. Don't forget to get some sealing foam for the end tanks to fill the gaps between the frame rail and the radiator.

Matt

 

The koyo radiator is more than Scooter needs for his use. I suggest finding something smaller that will go in with no modifications.

FYI, a replacement radiator goes in from the underside of the car. Trying to install from the top will require bending of AC lines, which is never a good idea.

 

^Agree...although I have no personal experience with the KOYO (~ 100% larger than stock), seems like I had less trouble with the install of my Fluidyne (~ 50% larger) than some have reported. Then again guys that have done the job multiple times insist it's nearly P n P. At any rate, the Fluidyne construction was excellent and it's been in my streeted car for about 10 years with no issues. Cut a couple sections of the box out to fit against the radiator faces and drop the swaybar mounts and mounting bolts for the AC condenser. IIRC, it'll slide up from the bottom pretty easily.

Option #2 is to buy a brand new OEM radiator. Not sure of the costs these days, but I think they were pretty efficient and hell, the first one lasted 20+ years.

 

I went with a Mishimoto. Was just about a drop in. I had to trim the upper mounts to get the rad to sit parallel with the AC condenser. That's how I knew it was slightly off from the OE I took out.

 

I have a very good condition fluidyne rad (same as sgtblue mentioned) that I just removed from my car that had AC. It came very out easy. Has a wing type drain port on the bottom that is super handy. I believe they are discountinued but would let it go for $300 obo. I'm not a mechanic or anything and it was easy.

 

It can be very frustrating, if you don't search!

Yes, this is reported to be effective. The old school method was to flip the condenser brackets side to side, I guess. Gonna drop one in soon...

Also this! Fluidyne is better than stock and there are lots of rx7's not overheating on the stock rad. Believe it or not.
The average Rx7 would probably benefit more from setting the fan temps than from getting a huge radiator. Too bad you need a PFC to do it easy.

 

Stock is fine for the intended purpose of daily driving, but when you stress the engine (e.g. tracking it), stock is not sufficient. Fans are important if you are doing a lot of low speed driving or idling.