← Mazda Miata NB (1999-2005 US model years) problems

Corroded coolant mixing-manifold elbow (NB1)

Limited · Severity: Medium · Years: 1999-2000

Symptoms

Coolant leak from the small front elbow.

Cause

A forum thread reports the pressed-in elbow corroding and failing; other posters report the same, and similar parts elsewhere in the cooling system.

Fix (summary)

Replace rather than patch; thread suggests also replacing heater return pipe O-ring and radiator hoses.

Sources

• NB1 coolant mixing manifold small front elbow — MX-5 Miata Forum (forum thread; read 2026-10-15; search excerpt only)
• Miata problems/maintenance by year — miatayear.com (editorial; read 2026-10-15; search excerpt only)

Summaries are in our own words. Not repair instructions; consult the factory service manual.