# Thermostat sub valve full-open lift — minimum (NA6)

Canonical URL: https://miatatorque.com/spec/thermostat-sub-full-open-lift-na6/

Applicability: NA 1990–1993 (B6) — Other years inferred from 1990 factory evidence.

Confidence: fsm

1.5 mm {0.06 in} minimum at 100°C {212°F}

Always confirm against your factory manual. Match every restriction and follow all stages and procedure notes. Disputed claims must not be automatically resolved. The complete record below preserves every printed unit, source claim and procedure.

```json
{
  "id": "thermostat-sub-full-open-lift-na6",
  "name": "Thermostat sub valve full-open lift — minimum (NA6)",
  "aliases": [],
  "applies_to": [
    {
      "gen": "NA",
      "years": [
        1990,
        1993
      ],
      "engines": [
        "B6"
      ],
      "note": "Other years inferred from 1990 factory evidence."
    }
  ],
  "kind": "non-torque",
  "value_text": "1.5 mm {0.06 in} minimum at 100°C {212°F}",
  "procedure": {
    "notes": "Factory two-stage thermostat with separate main and sub valves. Visually check valve is airtight, then place thermostat and thermometer in water and heat the water. Do not apply these two-stage specifications to an aftermarket single-stage thermostat. Minimum lift at the specified full-open temperature."
  },
  "confidence": "fsm",
  "sources": [
    {
      "source": "fsm-1990",
      "page": "E–8 (PDF p. 138)",
      "as_printed": "Full-open lift\nSub : 1.5mm (0.06 in) min.",
      "verified_years": [
        1990,
        1990
      ],
      "document": {
        "id": "fsm-1990",
        "tier": 1,
        "title": "1990 Mazda MX-5 Miata Workshop Manual",
        "part_number": "1193-10-89C",
        "covers": [
          {
            "gen": "NA",
            "years": [
              1990,
              1990
            ],
            "engines": [
              "B6"
            ]
          }
        ],
        "url": "https://archive.org/details/1990-mazda-mx-5-miata-workshop-manual_202411"
      }
    }
  ],
  "jobs": [],
  "system": "cooling",
  "component": "inventory-pass-2026-10",
  "componentName": "Service measurements and fasteners",
  "sequence_diagrams": [],
  "url": "https://miatatorque.com/spec/thermostat-sub-full-open-lift-na6/"
}
```