Oil Cooler

Last updated: March 28, 2000

Stock 2nd Cooler Info

From: jwhite @ htc.honeywell.com (Jim White)
Date: 05/20/97 09:28 AM

Ok, I'll have a little pity on you as a way of passing on the pity other list members have had for me.

I'm in Minneapolis and have added several R2 parts to my '94 Touring including the strut bar, front air dam, and second oil cooler. Here are my notes on adding the oil cooler:

Item  Part Number   Description             Qty   $ (ea.)   Note
----  ------------  ----------------------  ----  -------  ---------
  1   N3A1-14-710B  Hose, oil                1     52.60   Eng. to #4
  2   9938-11-400   Bolt, connector          1      2.35   #1 to eng.
  3   9956-21-800   Gasket                   2      1.30   For #2
  4   N3A3-14-830A  Hose, oil                1    223.40   Btw. coolers
  5   9978-60-616   Screw, tapping           1      1.60   #4 to frame
  6   N3A2-14-780B  Bracket, oil cooler      1     22.40   Outer bottom
  7   9993-70-600   Nut                      3      1.75   For #8,#6,#13
  8   N3A3-14-700   Cooler, oil              1    366.05   Right side
  9   FB01-56-81X   Fastener                 3      1.05   #10 to #8
 10   N3A2-14-708   Duct, oil cooler         1     25.70   conn. to #8
 11   9078-60-630   Screw & washer           1      1.10   #8 to #6
 12   9978-60-812   Screw, tapping           0      1.05   #13 to frame
 13   N3A2-14-770B  Bracket, oil cooler      0      8.15   Inner top
 14   N3A1-14-622   Stopper, connector       3      5.05   Conn. clip

I tried to be careful, but WATCH OUT FOR TYPOS! Almost all of this is on page 1-i-6 of my '94 parts fiche (section 1500).

Prices shown are from Mazda Competition Parts and are for quantity one. Multiply by the quantity column to get total prices. Don't forget freight (UPS) and tax. Maybe $75 or so.

The notes are kind of terse, but if you look at the diagram on the fiche I think they'll make sense.

One of the #7 nuts is not obvious, the other two are shown on the diagram. It connects one of the brackets to the frame panel that runs vertically just in front of the coolant overflow bottle at the right front corner of the car. I had to remove the right wheelwell liner and the coolant overflow tank to get the nut on.

The connector clips in #14 aren't really necessary if you don't mind reinstalling the old ones, but the shop manual says replace and I wanted to be safe, so I ordered new ones for the three connections that had to be opened. The connectors that come with the oil cooler (#8) and hose (#1) include new clips. I also wrapped some tape around the connector to help ensure that the clips don't come off.

I removed my airbox, intercooler and battery just to make it easy to get to the hose connections and to remove the old hose from the engine to the left oil cooler. It might be easy to get to the hose connections from below, but the bolt that holds the hose at the engine block (#2) is right above the frame and behind a bracket holding the other hose (the one that doesn't have to come off). You might be able to re-use the old bolt, but not the gaskets (#3), and I figured for $2.35 it was a good idea to replace it. By the way, it's 23mm.

I didn't disconnect any coolant lines or the coolant tank that mounts on the intercooler. I just left it connected and moved it out of the way. I dropped the front swaybar and removed it's mounting brackets so that I could install the oil lines (#4) without removing the lower radiator hose.

I did drain the oil from the block before starting and used a pan to collect the remainder that came out of the hoses and existing cooler as I disconnected things. Check the oil cooler section of your shop manual (pages D-8 and D-9 in mine) before you start. It shows how to get to the nuts (two of #7) on the top side of the oil cooler by removing the headlight bezel.

I originally ordered items 12 and 13, the found out that I didn't need them because the bracket (item 13) was already on my car. All it was doing was providing a hole for a wiring harness mounting clip, but it was there. If you take off the right headlamp bezel or the right side air duct plate (on the bottom), you should be able to see if it's there.


Date: Thu, 14 Aug 1997 17:10:23 -0400
From: "MO'Dell"

I suspect very few folks (if anybody) has gone to the trouble to add a second oil cooler to a base, touring or PEP model RX-7. After driving at Rockingham in 95 degree weather, and watching my temps rise (I had never before seen the gauge move past halfway in 2 years!), I decided that I better do this mod.

I called Peter Farrell Supercars to ask about aftermarket kits, and they recommended I use stock parts. I couldn't get through to Pettit (answering machine).

Being impatient, I decided to make a stab at it without waiting for more input. I thought I might share with you what I am going through so far in my attempt to do so.

I located a newly wrecked '94 R-2 at a local junkyard (D&K Motors, Dunn NC, 800-322-1223 - the car has an intact motor and exhaust and appears bone stock, but the passenger compartment is wrecked - I hope he/she/they lived).

I paid them $200 (ouch) for the following items (which they removed for me under my supervision):

- - second oil cooler
- - the hose and copper tubing that runs from the first oil cooler to the
second oil cooler
- - the hose and copper tubing that runs from the second oil cooler back
toward the engine
- - the bracket for the second oil cooler
- - misc hardware - bolts, clips etc that held these items in place
- - the air ducting in front of the 2nd oil cooler
- - the hose that bolts to the bottom of the engine that connects to the
tubing on the second oil cooler - MAKE SURE YOU GET THIS AS THE ONE THAT

Mounting the 2nd oil cooler was relatively easy, but you will need to first mount the bracket. You remove the plastic cover on the right headlight to access the top mounting bolts. You will have to unbolt the windshield washer resevoir to mount the bracket. It's fairly straightforward.

HOWEVER the plumbing will be another matter. I haven't done this yet and it appears that I will likely have to pull the radiator in order to run the hoses and tubing, and also to have access to the bolt on the bottom of the engine that all this connects to. For a shadetree mechanic like me, this looks like an all day job, so I will have to find some time in the next few weeks to tackle this. I will post the results.

Crooked Willow Kit

Date: 8/2/99 1:16:45 PM Eastern Daylight Time
From: dkrumweide@coi-world.com

Well the day has finally come. We are ready to take orders for the oil cooler kit and get your cars cooler than they already are ;-)

We are accepting Visa and Mastercard as well as check, moneyorder or COD. The usual COD charges will apply and COD funds will only be accepted in money order or cashier's check.

Orders may be placed by e-mail reply to this message or at either one of the following numbers:

858.273.7735 - our home office - If you get voice mail please leave a number and best time to call back. I will get back to you the same day you call unless it seems too late in the evening. Best time to reach a human voice here is after 5:30pm Pacific time.

858.621.7353 - my daytime office - A good number to reach me most of the daylight hours ;-) (OK, mostly 7am to 5pm Pacific)

If replying by e-mail or voice message, please give shipping address, method of payment and any special shipping instructions (COD, etc.) along with a phone numbers and times to reach you. Please do not send any credit card numbers via e-mail or leave them on voice. GIVE THEM TO ME LIVE OVER THE PHONE ONLY. This is for your protection and my piece of mind...

Prices are as quoted all along:

   $795 - full 2 cooler kit 
   $595 - full 1 cooler add-on / R-model upgrade (replaces all OEM lines)

   $495 - full 1 cooler kit (full replacement for single cooler configuration)
   $60 - single sending unit "T" (tapped for 1/8 NPT unless otherwise
   specified, sending unit not included)

   $90 - dual sending unit "T"s (both tapped for 1/8 NPT unless otherwise
   specified, sending units not included)
   . $125/pair - Carbon Fiber ducts.

Thanks again to everyone for your interest and patience. We look forward to providing you with additional quality products and services in the future. If anyone has any other product ideas you'd like to see on the market, let us know -- we are very willing to work with our customers on a custom or production basis.

Duane Krumweide
Chief Operating Officer
Crooked Willow Composites, LLC

visit us at: http://www.crookedwillow.com/

e-mail to:


Date: Wed, 15 Mar 2000 23:15:08 -0800
From: Max Cooper (max@maxcooper.com)

It is not that easy to install. All the pieces fit correctly, but you have to take a lot of stuff off and working under the headlights is a PITA. However, it still seems worth it, especially if you are replacing one beat-up stock cooler with the dual kit (as I did). The Mocal coolers seem to stand up to the debris and stuff better than the stock ones - the fins don't flatten as easily. With the ducts, the cooling has to be much better than stock though I have no numbers to prove it.

Dual kit with coolers, lines, brackets, fittings, thermostat, etc. is $795. Compare that to about the same price just to ADD the second stock cooler from what I have heard. Plus, you get rid of the trouble prone quick release lines that have cost a list member or two their motor. The ducts are available at an additional cost - about $125 a set I think. The ducts are carbon fiber and fit really nicely. See the Crooked Willow site for complete pricing and installation information:

I just made a web page about it with some pics (including the ducts).


Date: Fri, 17 Mar 2000 00:32:18 -0800
From: Max Cooper (max@maxcooper.com)

> Not as thin and dense and therefore stronger - also less cooling
> per sq surface area

Well, the stock coolers are 11 rows and have a smaller external flow area if I remember correctly. The Mocal coolers are 19 rows with a bigger external flow area. I think the Mocal ones should offer more cooling based on these differences (with proper ducting).

> Not necessarialy better than the R1 coolers in new condition.

Not necessarily, but I would think the CWC coolers would offer more cooling as stated above. Plus, the CWC ducts offer a better seal against the cooler and are a single piece, so there are no leaks.

> Very reasonable price for turnkey kit

Pegasus has the coolers for $135 each and the thermostat for $83. Plus another $300 for fittings and hose (yes, really, I added it all up). That's over $650 in materials before shipping and assuming no waste. Don't forget the brackets and your development time. I think the CWC kits are a really good deal, too.

> I'll say it again, if you do not duct/force air to flow thru
> cooler you are wasting your money.
> Without ducting, 50% or more of the the air flow will bypass the
> cooler at speed (after all it is a flat plate that doesn't flow air
> compared to any other opening air can find.  This
> is also true of the IC and radiator

I think the ducts are key, too, that is why I ordered a set as soon as they became available. In Maximum Boost, Corky Bell says you only get about 25% of the air flowing toward an un-ducted intercooler. I assume the proportion would be similar for oil coolers and radiators.

Curiously, my stock oil cooler duct was missing the top part that rivets on, leaving a big hole. Even in perfect condition, the stock oil cooler ducts don't seal that well against the core and aren't sealed up very well otherwise. The CWC ducts seal well against both the cooler and the front fascia, and are one piece so they have no leaks. I was a little skeptical when I saw them off the car as they don't use any fasteners on the bottom and didn't have rubber seals on the cooler mating surface. Installing them left me with no doubts, however -- they fit snugly and are a nice, efficient design. I was simply deceived at first by their apparent simplicity.

ANOTHER IC DUCT RANT (sorry to all you who have read this before): You must use a duct if you have a stock-mounted intercooler. I cannot believe how many people don't use a duct or leave the intake hole in the stock duct open. Even if the duct is pinched down to less than 25% of the external flow area of the core, the duct is essential. Remember that the duct is pinched down to fit through the opening that is available. So, you can get 25% of the air that comes through that little hole without a duct (and even that is doubtful with the radiator there), or use a duct and get 100% of that air (and no hot radiator air). With a stock-mount IC, YOU NEED A DUCT. If you are using the stock duct with an aftermarket intake, COVER & SEAL THE HOLE.

I am not affiliated with CWC other than being a satisfied customer and taking some pictures of the kit for their web site. I don't make any money from the sale of the kits.


LDate: Mon, 12 Mar 2001 08:40:12 -0500
From: Scot Kight (skight@reliacom.com) >I think Dave said, at the last MADS, that the CWC dual oil coolers showed a >20 degree drop in the rear rotor whereas the stock second oil cooler would >show a 5 degree drop over the stock touring cooler.... I'm not certain, but >Dave (KD) will still remember, I'm sure.

Yep, I think he said 20 degrees. Before anyone goes crazy and say "How did he measure that!" He used a temp gun. You just point it at a surface and it shows you the temps.

DIY: Do It Yourself

Date: Sun, 6 Apr 2003 18:18:24 -0700
From: "Eric Ristine" (eric@ristine.net)
Subject: Braided oil lines and fittings! Everything you need to know!

Ok here is the shopping list!

You can use alloy or steel adapters and hose ends here. Steel are a bit harder to find but are MUCH MUCH cheaper. Cost of the steel are about half to a quarter of alloy. Over all you can save HUGE amounts of $$ using steel fittings. The other nice part is if you ever want to replace the oil cooler you can now do so very easily using an Earl's or Mocal oil cooler with -10 AN fittings. All you would need to do is to get some ducts and make some brackets to for the oil cooler, get a thermostat and you would be good to go. This would offer substantial price savings over the Crooked Willow Racing oil cooler upgrade kit.

(2x) 22mmx1.5 to -10 AN adapter (these go into the oil cooler) Steel are about $8 each

(2x) 18mmx1.5 to -10 AN adapter (these go into the stock oil filter pedestal and the front cover) Alloy are $11-15 each (I used alloy since steel were out of stock everywhere, steel are about $5 each)

(2x) large dowty bonded seal washer for the 22mm adapters(these are special washers that have an inner rubber seal.You could also substitute copper crush washers here.)$1.10 each

(2x) medium dowty bonded seal washer for the 18mm adapters(these are special washers that have an inner rubber seal.You could also substitute copper crush washers here.)$1.10 each

(1x) 6ft of -10 size braided line (Aeroquip part #FCA1006 $38) You need 24" to go from the cooler to the front cover and 44 1/4"-48" to go to the cooler to the oil filter pedestal.

(2x) -10 AN straight hose end. (for the oil cooler side)(aeroquip #FCM1014 $9 each)

(2x) -10 AN 90 degree hose end. (for the front cover and the oil filter pedestal)(Aeroquip #FCM4034 $22) I also found while installing my setup that a -10 AN 45 degree hose end on the predestal side would probably work better. That is part# FCM4024.

(1x) Teflon tape for your NPT and metric sides of all your adapters. DO NOT USE Teflon tape on AN threads. (667$1 at any hardware store)


This is for the oil pressure sensor (if you have an after market gauge and want to keep the stock sender as well) Or you could also buy Dave Gibson's (FC3S.org) sassy new 3rd gen oil filter pedestal and eliminate the parts needed below. Dave will also be offering a full kit with the above components to replace your stock hoses.

(1x) 1/8" NPT male to -4 AN male adapter (this goes into the stock oil pressure sender location)(Aeroquip #FCM2512 $3)

(1x) 1/8" NPT female to -4 AN male adapter (this adapts to the tee for the two sensors)(Aeroquip #FCM2721 $3.50 each)

(2x) -4 AN straight hose end (Russell #610010 $7.25 each)

(1x)About 1 foot of -4 size braided hose (Aeroquip #FCA0403 $15 for three feet)

(1x)Brass tee. This has two female 1/8" NPT openings to screw the sensors into and one male 1/8" NPT to put the above listed -4 AN adapter onto. (about $3 at my local hardware store)

Some resource links...

You can get just about all of the fittings and adapters from Mocal in Florida. http://www.batinc.net/mocal.htm

This place has the 18mm adapters http://www.anplumbing.com/shop/

These guys have literally EVERYTHING ON THIS list and are a great shop. I arranged a 10% discount if you mention the Socal7 RX7 club. http://www.ormebros.com/

This place was also VERY helpful and had the metric adapters in stock. http://www.thefittingsource.com/

Pics of my installation:



Date: Tue, 30 Mar 1999 13:21:39 -0800
From: Tim Stiles (tstiles@ptp.hp.com)

12A specific but this place can make any line you need.......

In my never ending search to find things I need for the lowest price possible I've found a better deal on the oil cooler lines Racing Beat sells. I took a set of the Racing Beat lines to Royal Brass Inc. in San Jose today to find out what they'd charge to make them. The total came to $75. A little better than the $104 you'll pay the other guys. These are - -10 braided lines with a teflon inner core with the fittings crimped on the ends. Rated to > 450 degrees. Here's the specs -- you might want to file this one away cause you're gonna need to replace those old lines eventually.

Long Line:

20.75" long, (1) straight AN -10 fitting, 1 90 degree AN -10 fitting

Short Line:

9.75" long, (2) straight AN -10 fittings

You'll still need to buy the AN -10 to metric adapters from Racing Beat or Mazdatrix in order to hook the lines to the motor and oil cooler. (3) AN -10 to 16mm and (1) AN -10 to 18mm

The last alternative is to order the fittings and 3 ft of line from Summitt, or purchase locally if you can find a shop that sells the stuff, and make the lines yourself. That's what I did a year ago. Only saved $10 - -$15 over the Racing Beat lines though.......live and learn.


Date: Fri, 26 Mar 1999 17:31:10 -0500
From: Sandy Linthicum (sandy_linthicum@mindspring.com)

Important consideration: stock oil cooler have a thermostat bypass valve built in to each one of them. This ensures oil temps come up to norm (about 180F minimum). Without this, normal driving will not get temps up where they need to be.

You need a quality oil thermostat (Mocal is what I am using) to do this (one more item to plumb and pay for). Cost is about $90. Get it with AN fittings to match your lines if you are using AN lines.

Mazda's stock fitting are NOT AN and are a pain to match up with. If you rebuild the engine you can drill and tap the oil port to make it an AN fitting (AN12 on my car, lines are huge)


Don't know who originally posted this, but here it is:

Sometimes the connection between the oil pressure sending unit and the wire to the oil pressure gauge gets loose or dirty. The way to fix this is to clean the metal tab on the sending unit with some 0000 steel wool, and then re-install the gauge wire using some electrolytic silicone gel (like some sets of spark plug wires come with) to seal out grime.

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