Toyota Diesel OEM 1KZT 1KZTE Thermostat HiAce Hilux Surf Land Cruiser Prado 90916-03121 90916-03118 90916-03119

Product Overview

Genuine OEM Toyota Thermostat Assembly compatible with 1993-2009 Toyota Land Cruiser, Prado, 4Runner, Hilux Surf, HiAce, and Hilux models with 1KZ-TE, 1KZT, 1KD-FTV, 2KD-FTV, and 1GD-FTV diesel engines. This essential cooling system component delivers precise temperature regulation and ensures optimal engine performance across a wide range of operating conditions. Available in three temperature ratings to match your specific cooling requirements, whether maintaining stock specifications, compensating for aging cooling systems, or optimizing performance for modified engines and demanding applications.

OEM Part Number(s) by Temperature Rating:

• 71°C (160°F): 90916-03121 (lowest temperature - enhanced cooling)
• 76°C (169°F): 90916-03119 (factory HiAce specification)
• 82°C (180°F): 90916-03118 (standard factory specification)
• 90916-03097 (superseded by above variants)
• 16346-67010 (thermostat gasket - included with some variants)
• 16346-30010 (replacement thermostat gasket)

Key Features & Benefits

• Multiple Temperature Options: Choose from 71°C, 76°C, or 82°C opening temperatures to match your specific cooling requirements
• Perfect Fit: Engineered specifically for Toyota 1KZ-series and 1KD-series diesel engines with precision tolerances
• OEM Quality: Genuine Toyota brass housing with precision wax element for reliable temperature regulation
• Performance Optimization: Lower temperature variants provide enhanced cooling for modified engines, heavy towing, high ambient temperatures, or aging cooling systems
• Complete Package: Includes a genuine Toyota gasket for proper sealing and leak-free operation

 

Temperature Selection Guide

82°C (180°F) - Standard Temperature: Original factory specification for most 1KZ-TE applications. Ideal for stock engines operating in normal conditions with properly functioning cooling systems. Provides optimal warm-up time and fuel efficiency under standard operating conditions.

76°C (169°F) - Factory HiAce Specification: Original equipment for Toyota HiAce vans due to their higher heat load from the enclosed engine bay design. Excellent choice for vehicles with moderate cooling demands, aging cooling systems showing early signs of reduced efficiency, or light towing applications in warm climates.

71°C (160°F) - Enhanced Cooling: The lowest temperature option for maximum cooling performance. Recommended for modified engines with increased power output, heavy towing and payload applications, operation in extremely high ambient temperatures, vehicles with compromised cooling system efficiency, or turbo diesel engines pushing higher boost levels than stock.

Technical Specifications

Part Type: Engine Coolant Thermostat Assembly
Engine Compatibility: 1KZT, 1KZ-TE, 1KD-FTV, 2KD-FTV, 1GD-FTV diesel engines
Material: Brass housing with precision wax element
Temperature Options: 71°C (160°F), 76°C (169°F), 82°C (180°F)
Mounting Type: Direct OEM replacement
Weight: 0.16 kg (0.35 lbs)
Includes Gasket: Yes (genuine Toyota gasket included)

Fitment

Year Range	Toyota Model	Engine Options
1993-2002	Land Cruiser 90 Series (KZJ70, KZJ71, KZJ78)	1KZT, 1KZ-TE 3.0L turbo diesel
1996-2009	Land Cruiser Prado (90, 120 Series - KZJ90, KZJ95, KDJ90, KDJ95, KDJ120)	1KZ-TE, 1KD-FTV 3.0L turbo diesel
1993-2002	4Runner / Hilux Surf (KZN130, KZN185)	1KZT, 1KZ-TE 3.0L turbo diesel
1988-2005	Hilux (various markets - KZN chassis codes)	1KZ-TE 3.0L turbo diesel
2001-2011	Hilux (KDN165, KUN25, KUN26)	1KD-FTV, 2KD-FTV diesel (D-4D)
1993-2004	HiAce (KZH100, KZH106, KZH110, KZH120, KZH130 series)	1KZ-TE 3.0L turbo diesel
1995-2002	Grand HiAce / Granvia	1KZ-TE 3.0L turbo diesel
2000-2009	Dyna / ToyoAce (select models)	1KZ-TE, 1KD-FTV diesel
Various	Fortuner (select markets)	1KD-FTV, 2KD-FTV diesel
Various	Innova / Kijang (select markets)	1KD-FTV, 2KD-FTV diesel

Important: This thermostat is specifically designed for 1KZ-series and 1KD-series diesel engines. Verify engine code compatibility before ordering. Temperature selection should be based on your specific cooling requirements and operating conditions. The 82°C variant is standard for most applications, while lower temperatures provide enhanced cooling for demanding conditions.

Installation & Maintenance

Installation Difficulty: Intermediate
Tools Required: Socket set, drain pan, coolant funnel, torque wrench, hose clamp, pliers
Professional Installation: Recommended for proper coolant system bleeding and testing

Maintenance Tips:

• Always replace the thermostat gasket during installation to prevent coolant leaks
• Use genuine Toyota Long Life Coolant (LLC) or equivalent for optimal performance and corrosion protection
• Properly bleed the cooling system after installation to eliminate air pockets that can cause overheating
• Monitor coolant temperature during initial test drive to verify proper thermostat operation
• Inspect radiator cap and cooling system hoses for adequate sealing and condition during thermostat service

 

Frequently Asked Questions

Q: What's included in the package?
A: Package includes the complete thermostat assembly with a genuine Toyota gasket (16346-67010 or 16346-30010) for proper sealing—no additional gasket purchase required.

Q: Which temperature rating should I choose?
A: For stock engines in normal conditions, choose 82°C (standard specification). For HiAce vans or moderate cooling enhancement, select 76°C. For maximum cooling performance, modified engines, heavy towing, or hot climates, choose 71°C. Lower temperatures provide earlier coolant circulation but may slightly increase warm-up time.

Q: Will a lower temperature thermostat harm my engine?
A: No, lower temperature thermostats are safe and beneficial for cooling performance. However, they may increase fuel consumption slightly during warm-up periods in cold climates. Toyota factory-specified the 76°C thermostat for HiAce applications, confirming lower temperatures are appropriate for these engines.

Q: Can I use these thermostats interchangeably across different 1KZ-TE model years?
A: Yes, these thermostats are compatible with all 1KZ-TE, 1KZT, 1KD-FTV, 2KD-FTV, and 1GD-FTV diesel engines from 1993-2011. The mounting design remained consistent throughout production.

Related Toyota Parts You May Need

• Water Pump Assembly  - Commonly replaced during major cooling system service
• Radiator Hoses (Upper/Lower) - Inspect and replace if showing age-related deterioration.
• Radiator Cap - Maintains proper cooling system pressure for optimal performance.
• Toyota Long Life Coolant - Genuine coolant formulated for maximum corrosion protection
  

 

Common Symptoms of Thermostat Failure

• Engine overheating or running excessively hot, especially under load or in traffic
• Engine taking abnormally long to reach operating temperature (thermostat stuck open)
• Temperature gauge fluctuating erratically between normal and hot readings
• Poor heater performance due to insufficient coolant temperature
• Coolant leaking from thermostat housing due to a deteriorated gasket
• Check engine light illuminated with coolant temperature sensor codes
• Reduced fuel economy from engine running too cold (stuck open) or too hot (stuck closed)

 

Why Choose Genuine OEM Toyota Thermostat

Critical Cooling System Component: The thermostat serves as the primary temperature regulation device in your Toyota diesel engine's cooling system. Unlike simple on/off switches, genuine Toyota thermostats use precision-engineered wax elements that progressively open and close based on coolant temperature, providing smooth temperature regulation that protects your engine from thermal stress.

Toyota's 1KZ-TE and 1KD-FTV diesel engines are renowned worldwide for exceptional reliability and durability in demanding applications. However, these turbo diesel engines generate significant heat under load, making proper cooling system function absolutely critical for long-term reliability. A failed or incorrect thermostat can lead to catastrophic engine damage from overheating, or reduced efficiency from running too cold.

Temperature Options for Every Application: Toyota's engineering team designed multiple thermostat temperature ratings to accommodate different vehicle applications and operating environments. The factory-specification 82°C thermostat provides ideal warm-up characteristics and fuel efficiency for standard conditions. However, vehicles with high heat loads like HiAce vans received 76°C thermostats from the factory, and the 71°C variant serves enthusiasts running modified engines or operating in extreme conditions.

Aftermarket thermostats often fail prematurely due to inferior wax element formulations, incorrect opening temperatures, or poor brass casting quality that leads to coolant leaks. Genuine Toyota thermostats maintain precise temperature specifications throughout their service life, ensuring consistent cooling performance year after year.

Investment in Reliability: For a cooling system component as critical as the thermostat, the modest cost difference between genuine Toyota and aftermarket alternatives provides exceptional value. A failed thermostat can lead to catastrophic head gasket failure, cylinder head warping, or complete engine seizure - repairs costing thousands of dollars that could have been prevented with a genuine OEM thermostat.

Don't compromise on this essential cooling system component. Choose the temperature rating that matches your operating requirements, and trust genuine Toyota OEM quality to protect your investment in one of the world's most respected diesel engine platforms.