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If your Scion xD is running hot or never reaches normal operating temperature, the thermostat is a likely cause. Choosing the right thermostat matters because it controls coolant flow, which affects engine performance, fuel efficiency, and cabin heating. This guide presents the top shortlisted thermostats for the Scion xD, each selected for correct fitment and dependable thermal response. We evaluated options against real-world concerns like opening temperature accuracy and sealing durability. Read on to see the models we shortlisted and what to look for when replacing your Scion xD thermostat.
Looking for other parts? See all Scion xD parts & accessories.
Top Picks at a Glance
| Best Reviewed A top-rated pick with lots of positive feedback | AISIN THT-011 Engine Coolant Thermostat |  |
| Most Popular A crowd favorite that many people choose with confidence | Toyota 90916-A3003 Replacement Thermostat (Genuine Toyota) |  |
| Best Quality Built to a higher standard if you want something more solid | YWPXMY Water Pump and Thermostat Kit for 1.8L Toyota 2008–2014 xD / 2009–2019 Corolla / 2009–2013 Matrix |  |
| Best Budget The cheapest option that still gets the job done reliably | MOCA Coolant Thermostat Housing Assembly |  |
| Most Sold A high-volume bestseller chosen again and again | ROVIKE Engine Thermostat (replaces 90916-A3003 / 90916-03129) |  |
| Best Value for Money The sweet spot between price and what you get | AISIN THZ-002 Engine Coolant Thermostat with Gasket |  |
| Best Overall The best all-around choice for most situations | Motorcraft Thermostat Assembly RT1254 |  |
1. AISIN THT-011 Engine Coolant Thermostat
| Manufacturer Part Number | THT-011 |
|---|---|
| OEM Part Number | 90916-03093 |
| Position | Center |
This AISIN THT-011 thermostat is a direct-fit replacement designed to reproduce factory-specified operating temperature and cooling behavior. It installs in place of the original thermostat and is used to regulate coolant flow so the engine reaches and maintains its correct running temperature. Notable aspects are AISIN's OEM-matched design and machined exterior that aim to deliver consistent opening temperature and reliable long-term performance. In practice the part is straightforward to install for a mechanically inclined owner or technician and customers report normal fan operation and stable highway coolant temperatures after installation. The unit does not include a gasket, so you should source the correct sealing ring separately during a service interval. Expect OEM-level function rather than performance tuning benefits; this is a like-for-like replacement focused on dependability rather than upgraded flow or altered temperature calibration.
Best for: Reliability-focused buyers who prioritize factory-quality replacements and want a dependable, like-for-like thermostat for routine repairs and preventive maintenance on their Scion.
Less Ideal for: Buyers looking to change engine warm-up behavior, increase cooling capacity, or use a performance thermostat should consider alternative products that specify different operating temperatures or flow characteristics.
- OEM-matched operating temperature for predictable engine warm-up and fan control
- Machined construction suggesting consistent build quality
- Widely reported fit and function on compatible Toyota/Scion engines
- Simple direct-replacement design makes installation quick for routine maintenance
- Gasket not included so an additional seal must be purchased for proper installation
- Not intended to change thermostat calibration or cooling performance beyond factory spec
Verdict Choose this AISIN thermostat if you want a dependable, factory-matching replacement for maintaining original cooling system behavior on your Scion.
2. Toyota 90916-A3003 Replacement Thermostat (Genuine Toyota)
| Brand | Toyota |
|---|---|
| Item model number | 90916-A3003 |
| Manufacturer Part Number | 90916-A3003 |
This is the genuine Toyota 90916-A3003 thermostat sold as a direct replacement for compatible Toyota and Scion engines. It installs into the thermostat housing to open and close at the specified temperature, controlling coolant flow to maintain proper engine operating temperature. Buyers will appreciate that it is a factory-quality part so fitment and valve operation match the original design, which simplifies a DIY swap or a quick shop replacement. The part is compact and straightforward to install for anyone comfortable draining some coolant and removing the housing, though some Scion xD installs may require removing nearby components for access. A notable omission is that a new gasket is not included, so plan to reuse the old gasket if it is in good shape or purchase the correct seal separately to avoid leaks. Expect long service life when installed correctly, and observe proper orientation of the jiggle valve during reassembly to ensure proper air bleed and cooling performance.
Best for: A convenience-driven buyer who wants a factory-quality, no-surprises replacement for routine cooling system repairs on a Scion xD and prefers parts that match the original design.
Less Ideal for: If you prefer a performance or variable-temperature aftermarket thermostat or want an all-in-one kit with a new gasket and hardware included, look at other options instead.
- Genuine Toyota factory-quality part for correct fit and operation
- Direct replacement design simplifies installation and ensures proper valve timing
- Compact, simple component that performs the thermostat function reliably
- Well-documented fitment with many users reporting successful installs
- Replacement gasket is not included with the thermostat
- Requires coolant draining and some disassembly to access the thermostat housing
Verdict Choose this genuine Toyota thermostat for a simple, reliable factory-match replacement for your Scion xD, but buy a gasket separately.
3. YWPXMY Water Pump and Thermostat Kit for 1.8L Toyota 2008–2014 xD / 2009–2019 Corolla / 2009–2013 Matrix
| Brand | YWPXMY |
|---|---|
| Material | Aluminum |
| Automotive Fit Type | Vehicle Specific Fit |
| Model | PXSB-006 |
This kit combines a replacement water pump with a thermostat and thermostat housing so you can renew the cooling system components in one job. It is designed for 1.8L Toyota engines used in the Scion xD and includes the pump, thermostat housing, and thermostat gasket to simplify installation. The pump casting appears clean and machined surfaces are smooth, the impeller turns freely by hand, and the housing is metal for better heat resistance compared with plastic units. The included thermostat lets you replace the temperature-sensing element at the same time to avoid a second teardown. On the downside the paper gasket supplied feels thin compared with factory-style gaskets, so you may prefer to fit a higher-quality gasket or use sealant for a more reliable long-term seal. For a performance-oriented owner wanting durable, factory-quality replacement cooling parts for the Scion xD, this kit bundles the key components and lowers labor by replacing both pump and thermostat together, though pro installation or careful gasket selection is recommended for long-term leak prevention.
Best for: Performance-oriented owners who prioritize reliable cooling system function and prefer replacing pump and thermostat together to minimize downtime and repeat labor.
Less Ideal for: Buyers seeking a plug-and-play OEM-branded part with factory packaging and original manufacturer gaskets should consider dealer or name-brand alternatives instead.
- Vehicle-specific kit that includes water pump, thermostat housing, and thermostat for a single replacement job.
- Metal pump housing and machined mounting surfaces improve heat resistance and fit compared with lower-quality castings.
- Pump rotates smoothly by hand on inspected units, suggesting good bearing/assembly quality and reduced risk of early failure.
- Included paper gasket is thin and may be less durable than OEM-style or thicker replacement gaskets.
Verdict A practical, performance-minded kit that replaces the Scion xD water pump and thermostat together with a sturdy metal pump but consider upgrading the thin supplied gasket for best long-term results.
4. MOCA Coolant Thermostat Housing Assembly
| Opening Temperature | 82℃ or 179.6°F |
|---|---|
| Manufacturer | OELINE Auto Parts |
| Brand | MOCA AUTOPARTS |
| Manufacturer Part Number | TH1089 |
This MOCA thermostat housing assembly replaces the factory housing and thermostat to control coolant flow and engine operating temperature. It is intended for direct-fit replacement on compatible vehicles and is typically used when the stock housing leaks, the thermostat sticks, or when performing routine cooling-system repairs. The listing notes an 82°C (179.6°F) opening temperature for the primary unit and includes the thermostat preassembled in the housing for a single replacement step. For a budget-focused repair this part delivers a straightforward swap-in solution that restores proper thermostat operation and can stop coolant leaks associated with a failed housing. Limitations include mixed fitment listings across many models so double-check that this variant matches the Scion xD application, and the part is an aftermarket unit rather than a factory brand which may have small differences in finish or long-term durability compared with higher-end replacements.
Best for: Practical, budget-conscious owners who prioritize an affordable, quick repair to restore cooling system function without paying for a premium brand; good for DIYers comfortable confirming fitment and doing basic coolant-system work.
Less Ideal for: Buyers seeking an exact factory-branded replacement with extended longevity or dealers doing warranty repairs should consider factory-quality alternatives instead.
- Preassembled housing and thermostat for one-step replacement
- Designed to match factory mounting points for direct-fit installation
- Specified thermostat opening temperature (82°C / 179.6°F) for predictable operating behavior
- Low-cost option that lets you repair cooling issues without major expense
- Aftermarket unit so long-term durability may differ from factory-quality parts
- Fitment listings cover many models which requires careful verification for Scion xD
Verdict A low-cost, preassembled thermostat housing that makes a fast DIY cooling-system repair possible, provided you verify Scion xD fitment.
5. ROVIKE Engine Thermostat (replaces 90916-A3003 / 90916-03129)
| Included Components | Engine Thermostat |
|---|---|
| Power Source | Battery Powered |
| Material | Metal, Plastic |
| Connectivity Protocol | Wi-Fi |
This ROVIKE thermostat is a straightforward replacement part that fills the same cooling-system role as factory thermostats: it opens at the specified temperature to let coolant circulate and closes to allow the engine to warm up. For Scion xD owners it is sold as a single engine thermostat intended to replace part numbers 90916-A3003 and 90916-03129 and is marketed as a direct-fit item. Installation is the same as any plug-and-play thermostat swap and is typically performed during routine cooling-system service. The listing highlights a metal and plastic construction and states the unit is tested before shipping. Practical benefits include an affordable option to restore proper engine warm-up and prevent overheating when the original thermostat fails. Limitations to note are fitment variability with some users reporting incorrect sizing on certain model years, so careful year/engine verification and physical comparison with the old thermostat are recommended before installation. Expect basic function without performance upgrades or thermostatspecific testing data provided by the manufacturer.
Best for: Risk-averse mainstream buyers who prioritize restoring reliable, factory-style cooling function on a Scion xD without paying dealer prices and who prefer a simple, replace-and-forget repair approach.
Less Ideal for: Enthusiasts seeking performance thermostats with known calibrated opening points or owners unwilling to verify physical fit before installation should consider other options.
- Matches common Toyota part numbers listed for replacement (90916-A3003, 90916-03129).
- Sold as a single, ready-to-install thermostat for routine cooling-system repairs.
- Constructed from metal and plastic and described as tested before shipping for basic reliability.
- Affordable alternative to dealer-sourced thermostats, useful for DIY maintenance.
- Fitment reports are mixed and some buyers found the unit physically smaller than factory parts for certain years.
- Manufacturer does not publish opening temperature or calibrated performance data.
- Listing lacks detailed installation hardware or gasket specifics, so additional parts may be needed.
Verdict A budget-friendly, direct-replacement thermostat option for Scion xD owners, but verify physical fit and the opening temperature before installation.
6. AISIN THZ-002 Engine Coolant Thermostat with Gasket
| Manufacturer Part Number | THZ-002 |
|---|---|
| OEM Part Number | KL01-15-171A |
| Position | Center |
| Exterior | Machined |
This AISIN thermostat is a straightforward factory-quality replacement that controls coolant flow by opening at the correct specified temperature to maintain engine operating range. It is intended for use as a direct-fit replacement during routine cooling system repairs and typically installs in place of the original thermostat using the included gasket. Notable features include OE-matched operating temperature, machined exterior, and a gasket in the set to simplify installation. In real-world use the thermostat delivers predictable temperature control and a reliable fit, which helps the engine warm to and hold its correct temperature for consistent heater performance and cooling. Some listings and user reports note fitment depends on engine variant so double-check compatibility for your Scion xD, and a few buyers have reported packages without a gasket so confirm the box contents before starting the job. This unit favors buyers who want a no-nonsense, factory-matched replacement rather than an aftermarket performance piece.
Best for: A practical optimizer looking for a reliable, factory-matched replacement thermostat that restores correct engine temperature control without extra features or performance tuning.
Less Ideal for: Drivers seeking a performance thermostat with altered opening temperatures or aggressive cooling behavior should consider performance-specific aftermarket options instead.
- Factory-matched operating temperature for predictable engine warm-up and cooling performance.
- Machined exterior and OEM-specified form, fit, and function for straightforward installation.
- Includes a gasket in the set to reduce parts needed for the repair.
- Made by a long-established parts supplier with consistent quality control.
- Fitment can vary by engine variant so compatibility must be verified before purchase.
- Some buyers report missing gasket in certain packages, so inspect contents on receipt.
Verdict A dependable, factory-matched replacement thermostat that delivers predictable cooling performance and solid value for routine repairs.
7. Motorcraft Thermostat Assembly RT1254
| Manufacturer | Motorcraft |
|---|---|
| Model | RT1254 |
| Exterior | Painted |
The Motorcraft RT1254 thermostat assembly is a direct factory-quality replacement designed to restore proper engine temperature control. It installs in place of a failed thermostat to reopen coolant flow at the correct temperature and is typically used during cooling system repairs or as preventive maintenance when servicing the water pump or gasket. The unit is built to Ford-approved standards and includes the thermostat mechanism and associated sealing hardware where applicable, so fitment aligns with factory housings and reduces the need for modification. In practice this means quicker installs, predictable warm-up behavior, and consistent mid-range gauge readings compared with worn or mismatched aftermarket units. Some listings and reports note the gasket or O-ring may not always be new depending on application, so double-check parts included for your specific service. This thermostat is a sensible choice when you want a dependable, factory-spec replacement that simplifies installation and keeps engine temps stable, though you should confirm included seals before starting the job.
Best for: Balanced owners who prioritize dependable, factory-spec replacements and straightforward repairs for routine cooling-system maintenance on their Scion xD.
Less Ideal for: If you need a performance thermostat with a higher or lower opening temperature for tuning, this stock-style unit is not the right choice.
- Factory-quality design for reliable, predictable engine temperature control
- Direct-fit replacement that aligns with factory housings for easier installation
- Consistent performance reported across many Ford family applications
- Supported by Motorcraft standards recommended by Ford Motor Company
- Some users report the seal or O-ring may not always be provided new with the unit
- Not all listings include detailed fitment notes for specific vehicle years
Verdict Choose the Motorcraft RT1254 when you want a reliability-focused, factory-quality thermostat that restores correct temperature control with minimal fuss.
Choosing the Right Scion xD Thermostat: Key Factors to Consider
Opening Temperature
The thermostat's rated opening temperature determines when coolant begins circulating through the radiator. A thermostat that opens too late can cause higher operating temperatures and stress the cooling system, increasing the risk of overheating. Conversely, one that opens too early prevents the engine from reaching optimal temperature, which can raise emissions and reduce heater output.
Choose a thermostat with an opening temperature that matches the vehicle manufacturer specification or the common aftermarket equivalent for the Scion xD. Consistent and repeatable opening behavior matters more than a marginally lower or higher rating because it affects long-term engine management and thermostat performance under load.
Seal and Housing Quality
The seal between the thermostat and its housing is a frequent source of leaks. A high-quality gasket or integrated seal resists compression set, coolant degradation, and thermal cycling. Poor sealing leads to coolant loss, air intrusion, and erratic temperature readings.
Material choice for the housing and seal—usually rubber, silicone, or molded composite—affects longevity. Look for thermostats with robust gasket designs or sealed housings to minimize the chance of a thermostat housing seal leak and reduce the need for repeated resealing during maintenance.
Material and Corrosion Resistance
Thermostat components sit in coolant that can be mildly corrosive, especially over many years. Brass, stainless steel, and certain engineered composites resist corrosion better than basic stamped metals. Corrosion can cause stuck valves, degraded actuation, and premature failure.
Selecting a thermostat built from corrosion-resistant materials helps ensure reliable operation in the Scion xD's cooling system. This also reduces the risk of deposits or scale interfering with valve movement, which can cause symptoms like engine overheating or running cold if the valve becomes stuck open or closed.
Valve and Spring Design
The internal valve and spring control how smoothly and predictably the thermostat opens and closes. A well-designed spring provides steady, proportional movement as temperature rises, which helps the engine reach and hold its target temperature without sudden changes.
Inferior springs can fatigue or bind, causing delayed opening or sticking. That can produce intermittent overheating or inconsistent cabin heating. Consider thermostats with proven valve and spring assemblies that emphasize smooth travel and minimal binding under thermal stress.
Fitment and Ease of Installation
Correct fitment is critical. A thermostat that does not match the Scion xD's housing geometry, flange, or mounting points can cause leaks or require additional modifications. Ease of installation also matters for routine maintenance; designs that align easily and use common fasteners reduce labor time and the chance of installation errors.
Check that the replacement part follows the vehicle's OEM flange dimensions and gasket interface. Thermostats that include clear gasket placement, required seals, or a direct housing replacement simplify the process and reduce potential rework after installation.
Thermal Response and Reliability
Thermal response describes how quickly and consistently the thermostat reacts to temperature changes. A reliable unit opens at the correct temperature and remains stable across repeated heat cycles. Poor thermal response can lead to temperature swings, reduced fuel economy, or heater performance issues.
Evaluate thermostats on expected longevity under normal driving conditions and under higher thermal loads. Durable components with consistent actuation profiles reduce the chance of symptoms such as thermostat symptoms overheating or the engine running cold if the device becomes stuck open.
FAQ
What are common signs of a failing thermostat in a Scion xD?
Common signs include the engine running hotter than normal, little or no heat from the cabin heater, or the engine taking unusually long to reach operating temperature. You might also notice erratic temperature gauge readings or coolant leaks near the thermostat housing. These signs often indicate the thermostat is stuck closed, stuck open, or the housing seal is compromised.
How can I test a thermostat without removing it?
You can monitor the temperature gauge and feel the upper radiator hose as the engine warms. The hose should remain cool until the thermostat opens and then gradually get hot as coolant flows. Sudden changes or no change in hose temperature as the engine warms may indicate a stuck thermostat. For a more definitive test, a shop can use a scan tool to watch coolant temperature and thermostat opening behavior under load.
Will replacing the thermostat fix overheating issues?
Replacing a malfunctioning thermostat often resolves overheating that is directly caused by a stuck closed valve or incorrect opening temperature. However, overheating can also stem from other issues like a failing water pump, clogged radiator, or low coolant level. It usually helps to diagnose the cooling system as a whole rather than assuming the thermostat is the only cause.
How long does a thermostat typically last in regular use?
Thermostat life varies but they commonly last many years under normal conditions. Longevity depends on coolant condition, driving patterns, and exposure to temperature cycles. Regular coolant maintenance and timely sealing repairs can extend thermostat service life, while neglect or corrosive coolant can shorten it.
What should I check when installing a new thermostat?
Confirm the part matches the vehicle's specified opening temperature and fits the housing flange. Inspect or replace the gasket or O-ring, clean mating surfaces, and torque mounting bolts to spec. Also check coolant level and bleed the system to remove trapped air for reliable operation after installation.
How We Chose the Best Scion xD Thermostat
We focused on items that directly address common operating issues on the Scion xD and prioritized components that restore proper cooling system function. Key evaluation criteria included opening temperature accuracy, build quality of the valve and spring, housing and gasket sealing, and compatibility with Scion xD coolant passages. We also considered corrosion resistance, material quality of housing components, and how straightforward the part is to install given stock mounting locations. We excluded universal or generic thermostats that require extensive modification, multi-vehicle kits without explicit Scion xD fitment guidance, and parts with unclear temperature ratings. The list emphasizes correct fitment, dependable thermal response, and long-term sealing performance rather than low-cost options that sacrifice durability.
Our full evaluation process is outlined in our review methodology.
Conclusion
When selecting a Scion xD thermostat, prioritize accurate opening temperature, durable seals, and corrosion-resistant materials. These factors most directly affect engine temperature control, cabin heating performance, and long-term reliability. Balance ease of installation and correct fitment with internal component quality. Addressing the thermostat and its housing seals as part of routine cooling system maintenance reduces the chance of recurring issues and helps the vehicle maintain stable operating temperatures.
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