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Radiator Notes
After many years of use, radiators DO go bad. Corrosion/crud build-up can weaken the core to where the only thing holding it together IS the caked on junk inside the radiator. A good way to lose an engine is to have a marginal, or bad radiator. It should be removed and rodded-out every few years by a competent radiator shop.
The original 2-row radiators are OK when in good shape, and used on stock engines. We offer an upgraded 3-row for 79-82 RX-7's. The 83-85 radiator have tanks on them that are very hard to stretch far enough to get a 3-row core in them. They cool better than 79-82 style because of their greater surface area, so if they are in good shape you should have no problem, even on modified engines.
Another point to remember is that if the air pump belt is not being used, and the fan clutch is either very good or a little stiff, the remaining belt will slip on the water pump pulley at higher RPM's. This obviously results in a great decrease in water circulation and cooling. The slippage is due to inadequate belt contact area on the water pump pulley. The fix is to either run the air pump belt, or to install our dual belt pulley(s) on the alternator (and the eccentric shaft if desired). With 2 belts contacting the water pump pulley there is no slippage.
Anti-freeze with rust and corrosion inhibitors should ALWAYS be used in rotary engines, and changed every year or two. Periodically check all belts and the water pump. There should be no side-to-side play in the water pump when the fan blades are pulled and pushed. Pay close attention to the pressure cap as the seal likes to swell up, which prevents pressure release.
Radiators
| 93-95 | ||||
| ALL Aluminum with
a 2-row core that is over 2" thick (more than twice the stock one). Excellent
cooling -- about as much as you can get into the stock
location. (Manual Transmission cars only) Part Number R1443KO |
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| 3-Pass Heavy Duty
version of the Koyo radiator above. This heavy duty version has a lower fin
count for improved air flow through the radiator and is a three pass system for
even greater cooling efficiency. Part Number R1443NKO |
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| Same style as the above
one, but for Automatics (it has the transmission cooler built into the
bottom tank)
Part Number 01-7505-0000 |
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| Original Equipment Mazda Radiator | Manual Transmission: 15-200A-N3A1 | |||
| Automatic Transmission: 15-200A-N3A2 | ||||
| Aftermarket Aluminum
Radiator Manual Transmission Only R-ALUM-FDC |
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| 86-92 Standard Duty Note: The plastic and aluminum radiators used on 86 and later RX-7's work quite fine, but are very hard to service or repair. We offer both the original equipment plastic type, and aftermarket brass replacement radiators for 86-92. (Listed as "metal" below) The aftermarket radiators fit both manual trans and automatic trans models. They have the overflow tube at the cap. If yours uses an overflow tube at the thermostat cover, you will have to plug the one on the radiator. |
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| Years | Description | Part Number | ||
| 86-88 | 2-row Metal M/T & A/T | 867-RAD | ||
| 2-row Plastic/Alum. M/T | 15-200D-N326 | |||
| 2-row Plastic/Alum. A/T | 15-200D-N327 | |||
| 89-92 | 2-row Metal M/T & A/T | 2006-RAD | ||
| 2-row Plastic/Alum. M/T | 15-2000-N350 | |||
| 2-row Plastic/Alum. A/T | 15-200A-N351 | |||
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| 86-92 Koyo All Aluminum Radiators | ||||
| 86-88 | Single Pass | R181KO | ||
| 89-92 | Single Pass | R1144KO | ||
| 86-92 Extra HD 2-Pass Heavy Duty version of the Koyo radiator above. This heavy duty version has a lower fin count for improved air flow through the radiator and is a two pass system for even greater cooling efficiency. Some special fitting required |
Dual Pass "U Flow" | R1144NKO | ||
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89-92 Left
Side Radiator Bracket (needed to mount a Koyo radiator to OEM location) |
15-V120-N350 | ||
| 89-92 Right
Side Radiator Bracket (needed to mount a Koyo radiator to OEM location) |
15-V030-N350 | |||
| 79-85 Aftermarket fit both manual trans and automatic trans models. For manual trans the small tubes at the bottom are not used. |
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| 83-85 | 2-row M/T & A/T | 814-RAD | ||
| 79-82 | 3-row M/T & A/T | 699-RAD | ||
| Radiator Caps & Cap Assembly | ||
| Image | Year/Model | Part Number |
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79-85 (except GSLSE) | 15-2050-8871 |
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GSLSE (and all thru 78) | 15-2050-SE01 |
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86-95 (Pressure cap) | 15-2050-D316 |
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86-92 & 93-95 Flat Cap | 15-2050-KF01 |
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86-88 Cap Assembly w/overflow tube | 15-17YA-N326 |
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87-88 Cap Assembly w/o overflow tube (aluminum) | 15-17Y0-N323 |
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O-ring for above | 15-1740-N326 |
| Plastic Fasteners | ||
| These hold the plastic shroud around the radiator in place. | ||
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Lower Fan Shroud | 40-6580-9926 |
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Screw-Type | 50-6250-9926 |
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Push-Button Type | 56-81X0-FB01 |
| Thermostat Covers / Necks | |||
| Year | Part Number | Notes | |
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89-92 | 15-1720-N350 | Plastic, does not use a cap on the neck |
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89-92 | 15-1720-ALUM | Aftermarket ALUMINUM, does not use a cap on the neck |
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89-92 | 15-1750-N350 | OEM Radiator Filler Neck |
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86-88 N/T 5-speed | 15-172B-N326 | Aluminum, does not come with cap assembly |
| 86-88 Turbo & N/T Automatic | 15-172A-N318 | Aluminum, does not come with cap assembly | |
| O-Ring for 86-88 top, under the cap | 15-1740-N326 | ||
| Thermostat Cover Gasket | |||
| All thru 88 | 15-173A-1757 | ||
| 89-95 | 15-1730-N3C1 | ||
| Water Level Sensor (** see note below) and Seal | ||
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79-92** Sensor at top of radiator (does not include seal) |
15-610B-8553 |
| 93-95 (does not include seal) | 15-610A-N3A1 | |
| 79-95 Sensor seal | 15-6110-8553 | |
| **Note: The 89-92 Sensors (factory part number) are outrageously expensive. If the connector is simply changed over (it's just male/female bullet), then the much less expensive 79-88 one works fine. For this reason, we do not even list the OEM 89-92 sensor. | ||
| Radiator Top Outlet Bleed Plug and Drain
Plug Supplied w/new sealing "O"-ring |
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| 86-92 Top and Drain Plug | 15-2030-N326 | |
| 93-95 Drain Plug | 15-2030-NF01 | |
| 93-95 Air Separator Tanks | ||
| Mazda OEM Part | 15-35XB-N3A1 | |
| Aluminum | AST-ALUM | |
| Cap For Aluminum Tank | STA10329 | ![]() |
| Radiator Overflow/Expansion Tank | ||
| 79-80 Tank Square | No Longer Available | |
| 81-85 Tank Round 12a Only |
15-350D-1052 | |
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86-92 | 15-350C-N332 |
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93-95 | 15-350B-N3A1 |
| These factory tanks are good quality, and they work much better than those cheap universal ones available at the local parts houses. If you are not familiar with how these systems work, it is quite simple. As the water in the radiator heats and expands, it is pushed out past the radiator pressure cap, and into the overflow bottle. When the system cools down, the excess water is pulled back into the radiator by the vacuum created when the water requires less space. This allows the radiator to maintain a full load of water. | ||
| NOTE !!!: If your bottle stays full, and yet the radiator seems to need water frequently (the low-level light/buzzer keeps coming on), the problem is usually a bad bottle-to-radiator hose or connection, or a small leak somewhere that is preventing the system from creating enough vacuum to pull the water back in. We locate these by pressurizing the system (with a hand pump-up unit), and then just waiting for the drips. Sometimes it can take a good while for the leak to show. Typical things are loose hose clamps, small pin holes in the radiator, or a bad water pump seal. Please also remember that the radiator cap seal MUST be good - they tend to rather frequently have the seal expand to larger than the radiator neck, which prevents the cap from working correctly. | ||
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