Coolant re-route?

[vtluu]

If you can find an allowance in the ITCS that specifically allows additional "heater water control valves" (or whatever you choose to call it), fine. But I'm betting you won't.

9.1.3.D.3.g:

Engine coolant fluid, coolant/heater hoses and clamps may be substituted. Heater hoses may be plugged. Heater water control valve(s) may be added or substituted. Heater core and hoses shall not be removed.

The Miata cooling problem is basically this: when Mazda took the 323 transverse B6 (and its 1.8L version the BP) engine and shoehorned it into a longitudinal configuration, they changed a couple things to mount the engine as far back in the engine bay as possible: they replaced the distributor with coil packs, and they moved the thermostat housing to the other end (now front) of the engine.

The problem is water now leaves the engine through the thermostat housing at the front of the engine (to the radiator) and re-enters at the water pump on the front of the engine as well, so there is very little flow of water towards the back of the engine (cylinder 4). Bigger radiators etc. don't address this problem.

The coolant re-route kit restores the original water flow direction through the engine as it was intended.