Radiators, Caps, Water Level Sensor

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
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
Same style as the above one, but for Automatics (it has the transmission cooler built into the bottom tank) Part Number 01-7505-0000
Original Equipment Mazda Radiator			Manual Transmission: 15-200A-N3A1
			Automatic Transmission: 15-200A-N3A2
Aftermarket Aluminum Radiator Manual Transmission Only R-ALUM-FDC
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.
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
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
		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.
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
	79-85 (except GSLSE)	15-2050-8871
	GSLSE (and all thru 78)	15-2050-SE01
	86-95 (Pressure cap)	15-2050-D316
	86-92 & 93-95 Flat Cap	15-2050-KF01
	86-88 Cap Assembly w/overflow tube	15-17YA-N326
	87-88 Cap Assembly w/o overflow tube (aluminum)	15-17Y0-N323
	O-ring for above	15-1740-N326

Plastic Fasteners
These hold the plastic shroud around the radiator in place.
	Lower Fan Shroud	40-6580-9926
	Screw-Type	50-6250-9926
	Push-Button Type	56-81X0-FB01

Thermostat Covers / Necks
	Year	Part Number	Notes
	89-92	15-1720-N350	Plastic, does not use a cap on the neck
	89-92	15-1720-ALUM	Aftermarket ALUMINUM, does not use a cap on the neck
	89-92	15-1750-N350	OEM Radiator Filler Neck
	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
	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
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
	86-92	15-350C-N332
	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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