can a new thermostat be bad in car

[McCayden]

Yes, a brand new thermostat can be defective right out of the box. While it's not the most common issue, manufacturing defects do occur. A faulty new thermostat will cause the same problems as a worn-out one, primarily preventing your engine from reaching its optimal operating temperature or causing it to overheat.

The most obvious sign of a bad new thermostat is that the engine temperature gauge needle stays in the cold zone or takes an exceptionally long time to move, even after driving for several miles. You might also notice poor heater performance, as the heater core relies on hot coolant. Conversely, a thermostat stuck in the closed position will cause the engine to overheat rapidly because coolant cannot circulate to the radiator.

Common Symptoms of a Faulty Thermostat:

Symptom	Description	Likely Thermostat State
Engine Overheating	Temperature gauge climbs to the red zone, warning light illuminates.	Stuck Closed
Long Warm-up Time	Engine takes more than 10-15 minutes of driving to reach normal temperature.	Stuck Open
Poor Heater Output	Little to no warm air comes from the vents inside the car.	Stuck Open
Erratic Temperature Gauge	Gauge fluctuates wildly between hot and cold.	Sticking Intermittently
Coolant Leak	Visible coolant leak or puddle near the thermostat housing.	Gasket Failure

Before condemning the thermostat, it's worth checking the coolant level first, as low coolant can cause similar symptoms. If the coolant is full and these symptoms persist, the new thermostat is the primary suspect. Replacing it is generally a straightforward repair, but it's crucial to properly bleed the cooling system of any air pockets afterward to prevent further issues.

[LukeMarie]

Absolutely. I bought a brand-name thermostat to fix an overheating issue, and the problem got worse. The car would overheat in minutes. I put the old one back in as a test, and it worked better, though not perfectly. The new part was just stuck shut. It was a hassle, but the auto parts store swapped it for another one under warranty, and the second one worked fine. It happens more than you'd think.

[McAnthony]

It's frustrating, but yes, new parts can be bad. It's not always about being stuck open or closed. Sometimes, a new thermostat might open at the wrong temperature. If it opens too early, your engine never gets hot enough to run efficiently, hurting your gas mileage. If it's lazy and opens too late, you're flirting with overheating. It’s a precision component, and even a small defect during manufacturing can throw everything off.

[FaithFitz]

From a reliability standpoint, a defective new thermostat is a known, though infrequent, occurrence. The failure is often due to a flaw in the wax pellet element inside the unit that expands with heat. If this mechanism is compromised, the valve won't open correctly. It underscores the importance of using quality parts from reputable brands, as their quality control standards are typically higher, reducing the chance of getting a lemon straight from the box.