How to Install a Racing Radiator
[Rob Robinette adds: Since this article was written the Mazda Comp radiator
has been modified to fit just like the stock radiator and installation is much
easier. You might consider doing the AST Elimination
while your radiator is out, it will be very easy.]
The following is my experience with installing a competition radiator in my 93 RX7. It
is simply my experience and is not intended as a step by step procedure. I am not
encouraging anyone to do this. Should you do it, please follow safe work practices,
especially regarding supporting the raised vehicle - youll be underneath it a good
bit. If you screw it up or hurt yourself, its not my fault! And please, cut me a
little slack - Im neither a mechanic nor an engineer; Im not exceptionally
bright, and Im a little mechanically challenged, so you may find ways to do things
that are much easier (I sincerely hope you do). A few vendors are mentioned by name; I
have no connection with any of them (or any other vendor for that matter) and listing them
specifically is not meant to be a recommendation. I did all the work alone in my garage; a
friend to lend a hand was be a great benefit.
Now, on to the good stuff. While installing new radiator hose clamps, I over tightened
the clamp on the upper radiator hose, cracking the plastic hose inlet (or whatever
its called). There seemed no secure repair possibility, so a replacement radiator
was in order. I contacted Mazda Competition Parts and was told of a competition radiator
that was a direct bolt in replacement (see below). The competition radiator sold by Pettit
Racing looks to be the same piece; Pettit claims "some fitting required."
The radiator is all aluminum (well, it looks to be all aluminum; there are no plastic
parts) and is thicker than the stock radiator. Also, there is no foam border at the sides
of the radiator like the stock unit has (more on this later).
I removed the stock radiator as per the instructions in the workshop manual. It goes
pretty much as shown there with the exception that the shop manual fails to mention the
two nuts on the upper corners of the radiator that must be removed; this omission is
pretty evident once you do it, and access to the nut on the left is the reason the battery
and battery carrier must be removed.
Once the old radiator is out, the various pieces must be transferred from the old to
the new. There are a few brackets that are pretty straightforward. The fan assembly must
also the transferred. The fan assembly has 3 rubber feet that fit in holes in brackets
attached to the bottom of the radiator. On mine, the holes didnt line up with the
feet; I solved this by slightly enlarging the holes with a Dremel tool. This was a really
The radiator with fans attached is returned to the car from below, just like the stock
unit came out. Getting the radiator positioned so the upper left side nut could be
reinstalled was a bit of a pain. The bolt the nut attaches to is actually a post on a
rubber insulator (for lack of a better term) and the radiator tends to push the post
forward so the post does not line up with opening on the radiator that you hope to get
over the post. There was one additional line in the area that I hadnt removed
(youll either see it or have already removed it); removing it (well, removing the
mounting bracket; you dont remove the line) allowed room to fit my hand in the area
and hold the rubber insulator as the radiator is pushed into position.
Now comes the real fun. The air conditioning condenser is attached via 4 brackets. One
of these (the lower right) cannot clear the aluminum "piece" on the side of the
radiator (this "piece" was foam on the stock unit, so this sort of thing
wasnt a problem). I made a rectangular "notch" in the aluminum piece that
allowed the bracket to be installed. This can be done pretty easily with the radiator in
the car. I used the Dremel (if you dont have one, get one; I cant imagine
doing this job without it) to cut two sides of the rectangle and clamped a small pair of
vice grips on the aluminum "border." Be working the vice grips up and down, I
was able to break the aluminum, leaving a rectangular opening for the a/c condenser
bracket. The right upper a/c condenser bracket was also a problem. It attaches to a gold
colored bracket that is held on by a bolt; I simply could not get the hole on the a/c
condenser bracket to line up with the threaded hole in the "gold" bracket. I
finally had to grind down the gold bracket to move the threaded hole into position so the
bolt from the a/c condenser bracket could meet it. Your fitting problems may be different,
so YMMV. Also, I tried all the possible combinations of installing the brackets in
different orders to see if that would help, but it didnt.
At this point your troubles arent over. There are a couple of a/c lines that
travel from the condenser to the receiver-drier and, maybe, the compressor (didnt
really trace these down, so Im not sure exactly which ones they are, but youll
see them), passing around the left side of the radiator. These lines rub on the aluminum
border on the side of the radiator (again, this was foam on the stock radiator). I used a
file to shave away enough of the aluminum to allow the lines to pass without rubbing; as
the tolerances are pretty tight, I stuffed a piece of bicycle inner tube in the space
between the radiator and the aluminum lines for a little extra protection. This was a real
pain and would be _much_ easier if done while the radiator is still on the bench
in the car. You could probably measure and get it right; if you decide to do this project,
Id be happy to measure what I did some time when the under tray is off. As I was
using a hand file mostly (not enough room to safely use the Dremel - those small, thin
aluminum lines are mighty close by), I was left with a concave "defect" in the
aluminum border to provide room for the a/c lines.
At this point, I thought I was home free. However, there was one more problem. My
radiator came without a drain plug. The drain plug from the stock radiator does not fit. A
call to Mazda Comp provided the information that this required a plug with ¼ inch NPT.
These are pretty readily available, and Randy at Mazda Comp supplied a part number for an
Earles plug, which I ordered from Summit Racing. Well, I still dont know what
thread size the bung (thats the piece welded to the radiator that has the threads
for the drain plug - one of the many things I learned during this project) had, but it
wasnt ¼ inch NPT. I got a tap and re-threaded the bung, and the plug seems to fit.
However, had I realized this problem was going to arise, I could have easily solved it by
getting a plug before the radiator went back in the car. Should you do this, make sure you
have a drain plug _before_ you put the radiator back in the car.
Well, there you have it. The hoses and electrical connectors are now reinstalled, and
everything seems to be working. Was this a beneficial upgrade? Beats me. Ive never
had overheating problems, but I only have the stock coolant temp gauge. Since heat is such
a problem with these cars, it seems like a reasonable thing to do to me.
If you try this and have specific questions, let me know; Ill try to answer them.
I hope you found the above information useful, or at least mildly entertaining. Good luck!
Source for Stock Style Radiator
Thanks for your generosity in replying to my need for a radiator ........
But I found one faster than I thought. I got a reconditioned one for about $180
delivered the next day (wow), from www.radiatorwholesalers.com
I was really surprised at their deal, but sure enough the next day I got my
radiator, I thought it would be a reconditioned one, but this is different from
the stock unit. For one thing it's all
metal or aluminum (weighs about 15-20 lbs) But it is also about 1/3 inch
Wider than the old one. It didn't fit perfect, but with some pliers and patience
I put it in. I installed it today and drove for about an hour in the SUN Diego
without any problems. I'm happy with my purchase, specially after being so close
to getting robbed by the DEALER.