# Thermostat sub valve initial opening temperature (NA6)

Canonical URL: https://miatatorque.com/spec/thermostat-sub-initial-opening-temperature-na6/

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

Confidence: fsm

83.5–86.5°C

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-initial-opening-temperature-na6",
  "name": "Thermostat sub valve initial opening temperature (NA6)",
  "aliases": [],
  "applies_to": [
    {
      "gen": "NA",
      "years": [
        1990,
        1993
      ],
      "engines": [
        "B6"
      ],
      "note": "Other years inferred from 1990 factory evidence."
    }
  ],
  "kind": "non-torque",
  "value_text": "83.5–86.5°C",
  "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. The source prints 182–188°F; printed metric controls under the policy."
  },
  "confidence": "fsm",
  "sources": [
    {
      "source": "fsm-1990",
      "page": "E–8 (PDF p. 138)",
      "as_printed": "Initial-opening temperature\nSub : 83.5—86.5°C (182—188°F)",
      "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-initial-opening-temperature-na6/"
}
```