Testing the thermostat isn't difficult on the 1992-2001 2.2L Toyota Camry. In this tutorial, I'll explain how to test the thermostat step by step with an infrared thermometer gun (also known as an infrared laser).
With your test results, you'll quickly and easily find out if the thermostat is stuck open or stuck closed.
Contents of this tutorial:
APPLIES TO: This tutorial applies to the following vehicles:
- 2.2L Toyota Camry: 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001.
These other tutorials may come in handy:
- Common Causes Of Engine Overheating (1992-2001 2.2L Toyota Camry).
- How To Test The Radiator And Condenser Fan Motor (1992-2001 2.2L Toyota Camry).
- How To Test The Radiator Fan Switch (1992-2001 2.2L Toyota Camry).
- How To Test For A Blown Head Gasket (1990-2001 2.2L Toyota Camry, Celica).
Important Suggestions And Tips
TIP 1: You don’t need a scan tool to test the thermostat. This tutorial shows you how to use an infrared thermometer gun (also called a laser thermometer) to get the job done.
If you do have a scan tool capable of reading OBD I live data (for 1992–1995 vehicles) or OBD II (1996 vehicles), feel free to use it instead of the infrared thermometer to monitor the engine coolant temperature.
TIP 2: Never open the radiator cap when the engine is hot. If you need to add coolant or water to the radiator, always wait for the engine to cool down completely.
TIP 3: Make sure the engine is completely cold before starting the thermostat test. This ensures you’ll get accurate and reliable results.
TIP 4: Take all necessary safety precautions when working near a running engine to avoid injury.
Where To Buy The Thermostat And Save
The following engine coolant thermostat is from a known automotive part manufacturer (not a knock-off):
Symptoms Of A Bad Thermostat
The engine coolant thermostat in your 2.2L Toyota Camry will typically fail in one of two ways:
- Stuck Open: The thermostat remains open, allowing coolant to circulate constantly.
- Stuck Closed: The thermostat remains closed, preventing coolant from circulating.
- Bad gas mileage: Gas mileage takes a hit because the engine doesn’t reach its optimal operating temperature.
- Heater malfunction: During winter, the heater won’t provide warm air.
- Low temperature gauge reading: If your vehicle has a temperature gauge, it will always show a low reading or none at all.
- Emission test failure: Your vehicle may not pass the state emission test.
Most people are surprised to learn how much a stuck-open or missing thermostat can affect gas mileage, but it’s true!
Symptoms of a stuck closed thermostat
- Engine overheating: The engine temperature rises to dangerous levels.
- Cooling fans ineffective: The cooling fans turn on, but the engine doesn’t cool down.
- Maxed-out temperature gauge: Vehicles with a temperature gauge will show it maxed out.
- Temperature light on: If equipped with a temperature light, it will illuminate brightly, warning you of an engine meltdown.
OK, let's get testing.
Thermostat Performance Test
To get the most accurate results from your thermostat test, start with a completely cold engine.
If your Camry's engine has been running, allow it to cool down fully before beginning the test.
My go-to method to speed up the cooling process is using a box fan. Place the fan over the engine and let it run for 20 to 30 minutes until the engine is completely cold.
As mentioned earlier in this tutorial, we’ll be using an infrared thermometer to test the thermostat’s performance. If you don’t have one, check out my recommended tool: KIZEN Infrared Thermometer Gun (LaserPro LP300).
NOTE: The OEM thermostat temperature is 195° F.
CAUTION: You'll be working around a running engine. Take all necessary safety precautions.
These are the test steps:
PART 1:
- 1
With the engine off, open the hood.
- 2
Check the engine coolant level. Top it off if necessary.
CAUTION: The engine must be cold before removing the radiator cap. - 3
Check the temperature of the upper radiator hose. You can use your hand.
The hose should be at ambient temperature. If the hose is hot, let the engine cool down completely.
NOTE: The upper radiator hose is the one that connects to the thermostat housing on the engine. - 4
Take a temperature measurement directly from the round dome shape of the thermostat housing with your infrared thermometer gun.
IMPORTANT: Point the laser at the bulb shape of the thermostat housing. See photo 2 of 2 above. - 5
You should see a temperature within 10 degrees of ambient temperature on your infrared thermometer gun's display.
PART 2:
- 6
Start the engine. Monitor the temperature as the engine runs.
- 7
At 150° Fahrenheit (65° C) on your infrared thermometer, check the temperature of the upper radiator hose.
The upper radiator hose should still be at the ambient temperature you noticed in step 3. If so, continue to step 8.
If the hose is hot, you can conclude the thermostat is stuck open or missing. Replace the thermostat. - 8
At 200° Fahrenheit (93° C) on your infrared thermometer, check the temperature of the upper radiator hose.
At this temperature point, hot coolant should be circulating from the engine into the radiator, and the upper radiator hose should now be hot to the touch. - 9
Turn the engine off.
Let's take a look at what your test result means:
CASE 1: The upper radiator hose got hot at 200° F. This is the correct and expected test result. This test result lets you know that the thermostat is functioning correctly.
CASE 2: The upper radiator hose WAS NOT hot at 200° F. If the radiator hose was still at ambient temperature (cool to the touch), you can conclude that the thermostat has failed and is stuck in its closed position.
A thermostat that is stuck in its closed position will NOT allow coolant to circulate between the engine and the radiator, causing the engine to overheat.
Replacing the thermostat will solve the issue.
CASE 3: The upper radiator hose was hot at 150° F (or less). This test result lets you know that the thermostat has failed and is stuck in its open position.
A thermostat that is stuck in its open position will allow coolant to circulate into the radiator at all temperatures. This type of thermostat failure will prevent the engine from reaching its normal operating temperature.
Replacing the thermostat will solve the issue.
Engine Thermostat Basics
The engine coolant thermostat is a critical component of your 1992–2001 2.2L Toyota Camry’s cooling system. It plays a vital role in maintaining the engine's optimal operating temperature, which ensures the best engine performance and reduced emissions.
Here’s why it’s important:
- A cold engine requires more fuel to run.
- As the engine warms up to its normal operating temperature, it needs less fuel, which lowers hydrocarbon emissions.
In simple terms, the thermostat helps regulate the engine’s temperature, enabling it to run efficiently and minimize emissions.
How It Works In The Cooling System
- Starting the engine (cold engine):
- The thermostat is closed and the radiator fan is OFF.
- Coolant circulates only within the engine, gradually absorbing heat.
- Engine warm up:
- As the coolant temperature rises, it reaches approximately 195°F. At this point, the thermostat opens.
- Hot coolant begins to circulate between the engine and radiator, allowing heat to dissipate through the radiator.
- Activating the radiator fan:
- The coolant temperature continues to rise even after the thermostat opens.
- The coolant temperature switch, located near the radiator, monitors the temperature.
- When the switch detects coolant reaching around 220°F, it activates the radiator fan relays.
- The fan turns on, pulling more air across the radiator to cool the circulating coolant.
- Cooling the engine:
- Cooler coolant from the radiator flows into the engine, lowering its temperature.
- As the coolant temperature drops further, the coolant temperature switch turns the fan OFF.
- The thermostat may close if the coolant becomes too cool, allowing the process to start over.
This cycle of warming and cooling repeats continuously while the engine runs, ensuring that the engine stays within its optimal temperature range.
More 2.2L Toyota Camry Tutorials
You can find a complete list of 2.2L Toyota Camry tutorials and wiring diagrams in this index:
Here's a sample of the tutorials you'll find there:
- How To Test Engine Compression (1990-2001 2.2L Toyota Camry, Celica).
- How To Test The TPS With A Multimeter (1997-2001 2.2L Toyota Camry).
- How To Test For A Blown Head Gasket (1990-2001 2.2L Toyota Camry, Celica).
- How To Test The Throttle Position Sensor (1992-1996 2.2L Toyota Camry).
If this info saved the day, buy me a beer!
