How do I know if my Dodge Journey thermostat is bad?

If your Dodge Journey is overheating, running cooler than normal, or the heater stops delivering warm air, the thermostat could be the culprit. A quick assessment can help you determine whether a replacement is likely needed. In many cases, a faulty thermostat is the most common cause of cooling and heating symptoms in these vehicles.

The thermostat sits in the cooling system and regulates when coolant flows between the engine and radiator. When it fails, it can either stay closed, causing rapid overheating, or stay open, allowing the engine to run cooler than intended and reducing heater effectiveness. Understanding the symptoms and performing a few checks can help you decide if you should replace it or seek professional help.

Common signs your Dodge Journey thermostat may be failing

These symptoms are typical indicators that the thermostat could be failing. If you notice one or more of them, it's worth inspecting the cooling system and testing the thermostat.

• Engine overheats or the temperature gauge climbs toward the red zone, especially after a short drive or idling.


• Heater stops delivering warm air or only blows cool air, particularly at idle or begin driving.


• Engine runs unusually cold for longer than normal after startup, delaying reaching normal operating temperature.


• Temperature gauge shows erratic readings or fluctuates between hot and cold unexpectedly.


• Coolant leaks around the thermostat housing or upper radiator hose, or there is a noticeable loss of coolant without obvious external leaks.


• Check engine light or coolant-related codes appear on a scan tool (for example, codes related to engine temperature or coolant system).

If you notice several of these signs together, the thermostat is more likely the source of the problem. However, other cooling-system issues—such as a failing water pump, a clogged radiator, a faulty radiator cap, or a malfunctioning temperature sensor—can produce similar symptoms.

How to diagnose and confirm a bad thermostat

The following steps help you systematically confirm whether the thermostat is at fault. Perform these checks with the engine cool and the vehicle on a level surface for safety.

1. Check coolant level and condition. Ensure the reservoir and radiator (as applicable) are at the proper levels and coolant is clean. Low or dirty coolant can affect readings and cooling performance.


2. Start the engine and feel the upper radiator hose once the engine reaches operating temperature. If the hose remains cool or only becomes warm very slowly while the gauge shows normal or high temperatures, the thermostat may not be opening properly.


3. Observe engine temperature with a scan tool or the vehicle’s data display. Compare the Engine Coolant Temperature (ECT) reading to the actual engine temperature. If the ECT lags behind or never reaches the expected operating range (around 190–210°F or 88–99°C for many Dodge Journeys), the thermostat could be stuck open or slow to open.


4. Check for heater performance. If the heater delivers warm air only after the engine has fully heated, or never becomes hot, this can indicate a thermostat that is not regulating flow correctly.


5. Perform a thermostat location test. With the engine cool, inspect the thermostat housing and surrounding hoses for leaks, cracks, or a loose hose clamp. A stuck-open thermostat may show continuous coolant flow and a cooler engine, while a stuck-closed unit may show rapid overheating once the engine warms up.


6. Consider a physical thermostat test (optional and for experienced DIYers). If you can safely access the thermostat, you can remove it from its housing and place it in near-boiling water. A properly functioning thermostat should begin to open at roughly its rated temperature (often around 180–195°F or 82–90°C for many cars) and should show a noticeable flow once opened. Do not perform this test on a hot engine or without proper tools and cooling measures.


7. Rule out other cooling-system issues. If you find no obvious thermostat problem but symptoms persist, have a pressure test performed on the cooling system to check for leaks, and inspect the water pump, radiator, radiator cap, and hoses. A faulty cap or a failing water pump can mimic thermostat problems.


8. Decide on replacement. If tests indicate the thermostat is not opening/closing correctly and other components check out, replacement is usually the recommended fix. Replacing the thermostat also requires refilling and bleeding the cooling system to remove air pockets.

After performing these checks, you’ll have a clearer idea of whether the thermostat needs replacement or if another cooling-system component is at fault. If you’re unsure or lack the proper tools, a professional mechanic can confirm with diagnostic equipment and complete the replacement.

Replacing the thermostat: quick notes

If replacement is needed, plan for the following: obtain the correct OEM thermostat kit for your Dodge Journey, ensure you have a new gasket or O-ring, and follow the manufacturer’s torque specs. You’ll typically need to drain some coolant, remove the thermostat housing, take out the old thermostat, install the new one with the correct orientation, reseal the housing, refill coolant, and bleed the cooling system to remove air. If you’re not comfortable with these steps, a professional service is recommended to avoid air in the cooling system or improper reassembly.

Summary

In short, a bad Dodge Journey thermostat often shows up as overheating, a heater that won’t heat, or a temperature gauge that behaves irregularly. Confirm with a combination of visual checks (hoses and coolant level), live-data readings (engine coolant temperature vs. actual engine temperature), and, if necessary, a controlled thermostat test. If a faulty thermostat is confirmed, replace it along with the appropriate gasket and bleed the cooling system to restore proper engine temperature regulation. When in doubt, consult a qualified mechanic to avoid potential engine damage.

How to tell if it's the water pump or thermostat?

A coolant leak is the primary indicator of a faulty water pump, while overheating is the main symptom of a bad thermostat. Other signs of a bad water pump include grinding noises, a wobbly pulley, and visible corrosion around the pump itself, whereas a bad thermostat may cause the engine to fail to reach operating temperature or fluctuate erratically.
 
This video explains the symptoms of a bad water pump and how to diagnose it: 45sHVAC Mechanic YouTube · Jul 10, 2023
Symptoms of a failing thermostat

• Overheating: The engine temperature gauge climbs high, especially when idling. 
• Under-heating: The engine may not reach its normal operating temperature, even after a long drive. 
• Erratic temperature gauge: The temperature gauge fluctuates between hot and cold unpredictably. 
• Cooling fan stays on: The cooling fan may run constantly. 

Symptoms of a failing water pump

• Coolant leaks: A puddle of coolant, often green, yellow, or pink, is found under the front of the car. 
• Grinding or whining noise: A strange noise coming from the front of the engine. 
• Wobbly pulley: The pulley on the water pump is visibly shaky or loose. 
• Corrosion: Rust and deposits around the water pump can indicate a leak. 
• Overheating: While overheating is a symptom, it often occurs because the pump can no longer circulate coolant effectively. 

You can watch this video to see how to check if your water pump is working correctly: 58sOLDSKOOL TRIED & TESTEDYouTube · Jul 8, 2020
How to tell the difference

• Look for leaks: If you see a puddle of coolant, the water pump is the likely culprit. 
• Check for overheating: If the engine overheats, but there are no visible leaks, the thermostat is the more likely cause. 
• Inspect the pump: With the engine off, visually inspect the water pump for signs of a leak or wear. 
• Listen for noises: Grinding or whining noises are often a sign of a failing water pump. 

This video demonstrates how to check if your car's thermostat is working correctly: 57sYou WrenchYouTube · Mar 29, 2021
It's often recommended to replace both components at the same time, as they are often replaced together and are both crucial to the cooling system's function.

What is the most common problem with Dodge Journeys?

The most common problems with the Dodge Journey include electrical system failures (especially with the keyless entry and remote start), engine overheating due to coolant issues, and premature brake wear. Other frequent complaints involve water leaks, particularly in the interior, and transmission problems like slipping or hard shifting, particularly in certain model years.
 
This video discusses common Dodge Journey problems, including electrical, engine, and transmission issues: 52sOBD InsightsYouTube · Aug 2, 2024
Electrical problems 

• Remote keyless entry: Intermittent or complete failure of the keyless entry system is a frequently reported nuisance. 
• General electrical issues: Owners report problems with the Totally Integrated Power Module (TIPM), dead batteries, and malfunctioning power accessories. 
• Airbag malfunctions: This can include spontaneous deployment or failures, often indicated by a flashing airbag light. 

Engine and cooling system issues 

• Overheating: Particularly in models from 2009-2016, the engine can overheat due to a clogged coolant port in the thermostat housing. 
• Oil consumption: The 2.4-liter engine can consume a significant amount of oil. 
• Other engine complaints: Some models have experienced stalling, and the 3.6L engine can have issues with the oil cooler or radiator neck. 

Brake problems

• Premature wear: Owners report that brake pads and rotors wear out faster than expected. 
• Other issues: Problems include noisy brakes, sticking brake pedals, and ABS or ESC warning lights. 

Other common problems

• Interior water leaks: Water can leak into the cabin, particularly through the driver's door, and accumulate on the floor. 
• Transmission problems: Some model years, especially 2014-2015, are prone to transmission slipping or hard shifting. 
• Steering issues: Some owners report issues like a whining noise from the power steering pump. 

You can watch this video to learn about common Dodge Journey issues from a mechanic's perspective, including engine and transmission problems: 59sAlex The Car DoctorYouTube · Dec 31, 2021

How do I know if my thermostat is malfunctioning?

A thermostat may be bad if your HVAC system is not turning on, won't turn off, or is "short-cycling" (turning on and off rapidly). Other signs include the display being unresponsive or showing an incorrect room temperature, and the thermostat forgetting programmed settings. For a car, a bad thermostat can cause engine overheating or, conversely, overcooling (a prolonged warm-up period), as well as coolant leaks and poor fuel efficiency.
 
Home HVAC thermostat 

• System won't turn on or off: The most direct sign is that the heating or cooling won't start, or it runs continuously after the set temperature is reached. 
• Unresponsive controls: The screen may be blank, or the buttons might not work when you try to adjust settings. 
• Incorrect temperature: The temperature on the display may not match the actual room temperature, or it may fluctuate erratically. 
• Program settings are lost: If your thermostat has a programmable schedule, it shouldn't constantly forget the settings. 
• Short-cycling: The system turns on and off in quick succession instead of running through a normal cycle. 

Car thermostat

• Engine overheating: The temperature gauge consistently runs high or rapidly climbs to the red zone. This is often because the thermostat is stuck closed and not letting coolant flow to the radiator. 
• Engine is too cool: The temperature gauge stays at the low end of the normal range, or the engine takes a very long time to warm up. This can happen if the thermostat is stuck open. 
• Coolant leaks: Dripping liquid under your car can indicate a leak, which is sometimes related to a failing thermostat. 
• Heater problems: The heater blows cold air even after the engine has been running for a while. 
• Poor fuel efficiency: The engine runs inefficiently for too long because it doesn't reach its optimal operating temperature. 

How do I know if my Dodge car thermostat is bad?

1. Overheating and Overcooling. Overheating is the most common symptom of a failing thermostat.
2. Coolant Leaking. If you have experienced problems with overheating or notice liquid dripping under your car, it is a sure sign of a coolant leak.
3. Strange Sounds and Temperature Changes.
4. Heater Problems.