Owners of some 2006 Mazda Miata models may complain of poor heater performance at idle. According to Mazda, the condition usually occurs when the car is parked on a downward incline or braked hard before the engine reaches normal operating temperature.
Air bubbles in the heater core are the likely cause of the heater problems. Installing a new-design water hose, part No. LFG1-15-183B, between the radiator and thermostat housing and bleeding the cooling system should eliminate the heater troubles.
Here's the procedure:
- Begin by removing the existing water hose between the radiator and thermostat housing.
- Now, install the new hose, making sure the marks on the hose align with the marks at the metal connections. Using a special retaining clip, part No. AJ57-13-243A, secure the new water hose, heater core hose and power steering hose together at the location shown in the illustration.
- Continue the repair by filling the radiator's overflow tank with coolant until the level reaches the "full" mark on the side of the tank.
- Install the radiator cap.
Now start the engine and allow it to idle until normal operating temperature is reached. To bleed the system, run the engine at 2,500 rpm for approximately five minutes. Let the engine return to idle, then quickly raise the engine speed to 3,000 rpm for five seconds, followed by five seconds of idling. Repeat the bleeding sequence at least five more times.
To complete the fix, shut the engine off and let it cool, then check and adjust the coolant level in the overflow tank.
"Factory Fixes" is written by Jim DePalma, a 30-year veteran of the auto repair business who has served stints as a service manager, parts manager and ASE-certified technician. His column provides vehicle manufacturers' authentic factory technical service bulletins (TSBs) that have been condensed for easier reading. Mr. DePalma advises that techs always check with a dealer or repair information system for the latest revisions before starting to work on a vehicle. He can be reached via email at [email protected].