The Heat Is On

With some minor tube and hose work, the FE3 will keep you warm inside and out.

The stock FE3 heater core returns to the engine in a similar manner as all Miata engines- a hard tube from the core running under the exhaust manifold to the water pump mixer. Though the FE3’s tube runs around the back of the block, so some modification is needed to end it near the heater core inlet at the firewall.

In my case the mod included cutting and welding to get the hard line up high, away from the turbo downpipe. The lower line was originally a piece of hard tubing connected to the core and head with short pieces of hose.

The connection at the rear of the head was post thermostat. That worked sufficiently until the first super cold day came along.

After driving two miles in freezing temps, I found new motivation to move the heater core feed. I removed the stock thermoswitch for the fan, handing over fan control to the ecu. That sensor hole was then overbored and threaded for a larger barb fitting.

The clerk at the parts store gave me free reign behind the counter to search for the perfect hose– which I found. The new hose passes over the CAS to the heater core feed and delivers nearly instant heat on cold days.