Engine Coolant Thermostat Guide for 1981-1990 Isuzu Pickup
Keep your classic Isuzu Pickup's engine from overheating or running too cold by understanding this critical part.
- A failing thermostat can cause your engine to overheat (stuck closed) or run too cold (stuck open).
- Overheating is a critical issue; pull over immediately to prevent engine damage.
- For this truck, quality aftermarket brands like Gates and Stant are excellent, affordable choices.
- Always replace the thermostat gasket at the same time as the thermostat itself.
Is Your Isuzu's Thermostat Failing?
A thermostat is a wear item. After decades of service in a 1981-1990 Isuzu Pickup, it's not a matter of if it will fail, but when. The failure typically happens in one of two ways: stuck closed or stuck open. Both can cause problems for your engine.
🎬 Watch: 7 common symptoms of a failing thermostatStuck Closed: The Engine Killer
A thermostat stuck in the closed position is the most dangerous type of failure. It traps coolant inside the engine, preventing it from ever reaching the radiator to cool down. This leads to rapid overheating, which can cause severe and expensive engine damage like a warped cylinder head or blown head gasket. If you see your temperature gauge shoot into the red, you must stop the engine immediately.
Stuck Open: The Inefficient Failure
If the thermostat fails in the open position, coolant will constantly circulate through the radiator, even when the engine is cold. This makes it very difficult for your engine to reach its proper operating temperature. You'll notice the temperature gauge stays low, your heater blows lukewarm air, and your fuel economy may get worse. While not as immediately destructive as a stuck-closed failure, it can cause increased engine wear over time.
Choosing the Right Aftermarket Thermostat
For a vehicle from this era, finding a genuine Isuzu OEM thermostat can be difficult, and high-quality aftermarket parts are a perfectly reliable and affordable option. The key is to choose a reputable brand and ensure the temperature rating is correct for your truck's engine. Most thermostats for the Isuzu Pickup are rated to open at 82°C (180°F). Always replace the gasket when you replace the thermostat.
🎬 Watch this walkthrough of an Isuzu thermostat and hose replacementAftermarket Brand Tiers
- Tier 1 (Trusted & Recommended): Brands like Gates and Stant have a long-standing reputation for quality in the aftermarket world. Many professional mechanics and experienced DIYers trust these brands for their reliability, often considering them equivalent to OEM for older vehicles.
- Tier 2 (OEM Supplier/Reboxer): Beck Arnley specializes in parts for import vehicles and often re-packages parts from the original equipment manufacturers, making them a solid choice. Motorad is a massive manufacturer that produces thermostats for many other brands, including some Stant products. While some have had good experiences, others report inconsistent quality, so it's a bit of a gamble.
- Tier 3 (Value-Oriented): Brands like Calorstat and Facet are generally considered budget-friendly options. While they can function correctly, they may not have the same robust construction or long-term reliability as higher-tier brands. Given the low cost of even the best thermostats, it's usually worth spending a few extra dollars for a top-tier brand.
| Quality Tier | Brand Examples | Estimated Price |
|---|---|---|
| Tier 1 | Gates, Stant | $15 - $28 |
| Tier 2 | Beck Arnley, Motorad | $10 - $20 |
| Tier 3 | Calorstat, Facet | $8 - $15 |
Frequently Asked Questions (FAQ)
Do I need to replace the thermostat housing too?
Usually, no. You only need to replace the housing if it is cracked, warped, or heavily corroded, causing a leak. The thermostat itself is a separate part that fits inside the housing. Always clean the mating surfaces of the housing before installing the new thermostat and gasket.
What temperature thermostat should I use?
You should always use the temperature rating specified for your vehicle. For most 1981-1990 Isuzu Pickups, this is an 82°C (180°F) thermostat. Using a thermostat with a lower or higher temperature rating can negatively affect engine performance and efficiency.
Are there any recalls for the thermostat on my Isuzu Pickup?
No. Searches of the National Highway Traffic Safety Administration (NHTSA) database show no recalls or technical service bulletins (TSBs) related to the engine coolant thermostat for the 1981-1990 Isuzu Pickup.
Can I test my old thermostat?
Yes. You can place the old thermostat in a pot of water on the stove with a thermometer. As the water heats up, you should see the thermostat open around its rated temperature (e.g., 180°F). If it doesn't open, or if it's already open when cold, it has failed. However, given the low cost of a new part, it's almost always better to just replace a suspect thermostat.
🎬 See how to remove, test, and install a new thermostatHelpful Videos
Technical Specifications
OEM Part Numbers: 8943360690 8941718160 8942072171 8942072172 8971606540
Standard Temperature: 82°C (180°F)
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The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
- Isuzu Pickup: