How to diagnose and replace a faulty thermostat in a cooling system on Kia Optima?

To determine if the thermostat is at fault for a cooling system problem, it must be checked whether the coolant level is low, drivebelt tension is correct or the temperature gauge and light are working. If an engine takes long to warm up then its thermostat may have stuck in open position hence needs replacement. Conversely, if the engine runs hot but the outlet hose from radiator does not become hot, this implies that the thermostat may be stuck closed and would require replacing. Driving a vehicle without a thermostat will affect both emissions and fuel economy; thus it should never be done. Similarly, if outlet radiator hose is hot, this means that there is flow of coolant through it indicating that thermostat is open. However, when it's removed from vehicle you can perform more detailed test on the thermostat. A bad/defective one will remain open even at room temperature hence requiring replacement. For instance when cold water containing some suspended thermostats in it are heated while observing their temperatures as they keep opening up as to finally know if they meet specifications of their manufacturers or not. Furthermore note the temperature at which the valve starts to open and fully opens in contrast with manufacturer's specifications for replacing them afterward. Change it when specified openings and closings do not occur or when it gets stuck somewhere during operation. To dismantle such a component from an automobile one should first drain off all coolant stored in its reservoir; also disconnecting main pipe joints will aid during its removal process too.. In addition, remove old gasket between housing cover and body itself after freeing clips of fastening 2 parts together respectively before installing new one attached to valve having jiggle pin placed above highest point among other points found on automotive devices like housing covers where bolts must be tightened according to required torque values provided by manufacturer. Lastly refill coolant into overflow tank before running engines for sometime while checking any leakages or proper functioning relating to those car parts.

Genuine Kia Optima Thermostat

Engine Coolant Thermostat

Select Vehicle by Model
Select Vehicle by VIN

Select Vehicle by Model

Make

Model

Year

Select Vehicle by VIN

For the most accurate results, select vehicle by your VIN (Vehicle Identification Number).

18 Thermostats found

View related parts
Kia Optima Thermostat Assembly
Part Number: 255002B000
$19.02 MSRP: $26.75
You Save: $7.73 (29%)
Ships in 1-3 Business Days
ADD TO CART
Product Specifications
- Other Name: Thermostat
- Replaces: 255002B001, 255002B400
- Warranty: This genuine part is guaranteed by Kia's factory warranty.
Fits the following Vehicles:
- 2016-2020 Kia Optima | 1.6L - GAMMA | Sedan - 4Door 5P
View related parts
Kia Optima Thermostat Assembly
Part Number: 2550037200
$18.94 MSRP: $26.63
You Save: $7.69 (29%)
Ships in 1-3 Business Days
ADD TO CART
Product Specifications
- Other Name: Thermostat
- Warranty: This genuine part is guaranteed by Kia's factory warranty.
Fits the following Vehicles:
- 2000-2005 Kia Optima | High Grade, Middle Grade | 2.5L, 2.7L | 4 Door Sedan
View related parts
Kia Optima Control Assembly-COOLANT
Part Number: 256002G500
$119.00 MSRP: $170.25
You Save: $51.25 (31%)
Ships in 1-3 Business Days
ADD TO CART
Product Specifications
- Other Name: Control Assembly-Coolant Temperature; Control Assembly, Thermostat Unit
- Warranty: This genuine part is guaranteed by Kia's factory warranty.
Fits the following Vehicles:
- 2011-2015 Kia Optima | 2.4L - Theta 2 | Sedan - 4Door 5P
View related parts
Kia Optima Thermostat Assembly
Part Number: 2550026100
$18.84 MSRP: $26.50
You Save: $7.66 (29%)
Ships in 1-3 Business Days
ADD TO CART
Product Specifications
- Other Name: Thermostat
- Warranty: This genuine part is guaranteed by Kia's factory warranty.
Fits the following Vehicles:
- 2014-2015 Kia Optima | 2.0L - Theta 2 | Sedan - 4Door 5P
View related parts
Kia Optima Control Assembly-COOLANT
Part Number: 256002G600
$167.07 MSRP: $239.02
You Save: $71.95 (31%)
Ships in 1-2 Business Days
ADD TO CART
Product Specifications
- Other Name: Control Assembly-Coolant Temperature; Housing Assembly, Thermostat Unit
- Warranty: This genuine part is guaranteed by Kia's factory warranty.
Fits the following Vehicles:
- 2008-2010 Kia Optima | 2.4L - Theta 2 | Sedan - 4Door 5P
View related parts
Kia Optima Control Assembly-COOLANT
Part Number: 256002G545
$165.48 MSRP: $236.73
You Save: $71.25 (31%)
Ships in 1-2 Business Days
ADD TO CART
Product Specifications
- Other Name: Control Assembly-Coolant Temperature; Control Assembly, Thermostat Unit
- Replaces: 256002G540
- Warranty: This genuine part is guaranteed by Kia's factory warranty.
Fits the following Vehicles:
- 2011-2013 Kia Optima | 2.0L - Theta 2 | Sedan - 4Door 5P
View related parts
Kia Optima Control Assembly-COOLANT
Part Number: 2560025003
$214.20 MSRP: $297.50
You Save: $83.30 (28%)
Ships in 1-3 Business Days
ADD TO CART
Product Specifications
- Other Name: Control Assembly-Coolant Temperature
- Warranty: This genuine part is guaranteed by Kia's factory warranty.
Fits the following Vehicles:
- 2006-2008 Kia Optima | 2.4L - Theta FF | Sedan - 4Door 5P
View related parts
Kia Optima Thermostat Assembly
Part Number: 2550025001
$18.94 MSRP: $26.63
You Save: $7.69 (29%)
Ships in 1-3 Business Days
ADD TO CART
Product Specifications
- Other Name: Thermostat
- Warranty: This genuine part is guaranteed by Kia's factory warranty.
Fits the following Vehicles:
- 2006-2008 Kia Optima | High Grade, Middle Grade | 2.4L, 2.4L - Theta FF | 4 Door Sedan, Sedan - 4Door 5P
View related parts
Kia Optima Control Assembly-COOLANT
Part Number: 256002G540
$170.45 MSRP: $236.73
You Save: $66.28 (28%)
Ships in 1-3 Business Days
ADD TO CART
Product Specifications
- Other Name: Control Assembly-Coolant Temperature
- Replaced by: 256002G545
- Warranty: This genuine part is guaranteed by Kia's factory warranty.
Fits the following Vehicles:
- 2011-2013 Kia Optima | 2.0L - Theta 2 | Sedan - 4Door 5P
View related parts
Kia Optima Control Assembly-COOLANT
Part Number: 256002G560
$198.92 MSRP: $284.58
You Save: $85.66 (31%)
Ships in 1-3 Business Days
ADD TO CART
Product Specifications
- Other Name: Control Assembly-Coolant Temperature; Control Assembly, Thermostat Unit
- Warranty: This genuine part is guaranteed by Kia's factory warranty.
Fits the following Vehicles:
- 2014-2015 Kia Optima | 2.0L - Theta 2 | Sedan - 4Door 5P
View related parts
Kia Optima Thermostat Assembly
Part Number: 255002GGA0
$20.41 MSRP: $28.70
You Save: $8.29 (29%)
ADD TO CART
Product Specifications
- Other Name: Thermostat
- Warranty: This genuine part is guaranteed by Kia's factory warranty.
Fits the following Vehicles:
- 2016-2020 Kia Optima | 2.4L - Theta 2 | Sedan - 4Door 5P
View related parts
Kia Optima Thermostat Assembly
Part Number: 2550023010
$21.27 MSRP: $29.92
You Save: $8.65 (29%)
Ships in 1-3 Business Days
ADD TO CART
Product Specifications
- Other Name: Thermostat
- Replaces: 2550023001
- Warranty: This genuine part is guaranteed by Kia's factory warranty.
Fits the following Vehicles:
- 2008-2015 Kia Optima | 2.0L - Theta 2, 2.4L - Theta 2 | Sedan - 4Door 5P
View related parts
Kia Optima Thermostat Assembly
Part Number: 2550035540
$18.94 MSRP: $26.63
You Save: $7.69 (29%)
Ships in 1-3 Business Days
ADD TO CART
Product Specifications
- Other Name: Thermostat
- Warranty: This genuine part is guaranteed by Kia's factory warranty.
Fits the following Vehicles:
- 2006-2010 Kia Optima | High Grade, Middle Grade | 2.7L, 2.7L - MU | 4 Door Sedan, Sedan - 4Door 5P
View related parts
Kia Optima Thermostat Assembly
Part Number: 255002GTA0
$18.84 MSRP: $26.50
You Save: $7.66 (29%)
Ships in 1-3 Business Days
ADD TO CART
Product Specifications
- Other Name: Thermostat
- Warranty: This genuine part is guaranteed by Kia's factory warranty.
Fits the following Vehicles:
- 2016-2020 Kia Optima | 2.0L - Theta 2 | Sedan - 4Door 5P
View related parts
Kia Optima Control Assembly-COOLANT
Part Number: 256002GTA0
$167.83 MSRP: $240.10
You Save: $72.27 (31%)
Ships in 1-3 Business Days
ADD TO CART
Product Specifications
- Other Name: Control Assembly-Coolant Temperature; Thermostat Unit
- Warranty: This genuine part is guaranteed by Kia's factory warranty.
Fits the following Vehicles:
- 2016-2020 Kia Optima | 2.0L - Theta 2 | Sedan - 4Door 5P
View related parts
Kia Optima Thermostat Assembly
Part Number: 2550038001
Product Specifications
- Other Name: Thermostat
- Warranty: This genuine part is guaranteed by Kia's factory warranty.
Fits the following Vehicles:
- 2000-2005 Kia Optima | High Grade, Middle Grade | 2.4L | 4 Door Sedan
View related parts
Kia Optima Control Assembly-COOLANT
Part Number: 2560038020
Product Specifications
- Other Name: Control Assembly-Coolant Temperature; Housing Assembly
- Warranty: This genuine part is guaranteed by Kia's factory warranty.
Fits the following Vehicles:
- 2000-2005 Kia Optima | High Grade, Middle Grade | 2.4L | 4 Door Sedan
View related parts
Kia Optima Control Assembly-COOLANT
Part Number: 2560038025
Product Specifications
- Other Name: Control Assembly-Coolant Temperature; Housing Assembly
- Warranty: This genuine part is guaranteed by Kia's factory warranty.
Fits the following Vehicles:
- 2000-2005 Kia Optima | High Grade, Middle Grade | 2.4L | 4 Door Sedan

Kia Optima Thermostat

If you're in search of top-notch, reasonably priced OEM Kia Optima Thermostat, then you've found the perfect spot. Our website boasts an extensive inventory of Kia Optima Thermostat, all priced at the market's premier price. Rest assured, every genuine part we offer comes with a warranty straight from the manufacturer.

Kia Optima Thermostat Parts Questions & Experts Answers

Thermostat Assembly
2550025001
Q: How to diagnose and replace a faulty thermostat in a cooling system on Kia Optima?
A: To determine if the thermostat is at fault for a cooling system problem, it must be checked whether the coolant level is low, drivebelt tension is correct or the temperature gauge and light are working. If an engine takes long to warm up then its thermostat may have stuck in open position hence needs replacement. Conversely, if the engine runs hot but the outlet hose from radiator does not become hot, this implies that the thermostat may be stuck closed and would require replacing. Driving a vehicle without a thermostat will affect both emissions and fuel economy; thus it should never be done. Similarly, if outlet radiator hose is hot, this means that there is flow of coolant through it indicating that thermostat is open. However, when it's removed from vehicle you can perform more detailed test on the thermostat. A bad/defective one will remain open even at room temperature hence requiring replacement. For instance when cold water containing some suspended thermostats in it are heated while observing their temperatures as they keep opening up as to finally know if they meet specifications of their manufacturers or not. Furthermore note the temperature at which the valve starts to open and fully opens in contrast with manufacturer's specifications for replacing them afterward. Change it when specified openings and closings do not occur or when it gets stuck somewhere during operation. To dismantle such a component from an automobile one should first drain off all coolant stored in its reservoir; also disconnecting main pipe joints will aid during its removal process too.. In addition, remove old gasket between housing cover and body itself after freeing clips of fastening 2 parts together respectively before installing new one attached to valve having jiggle pin placed above highest point among other points found on automotive devices like housing covers where bolts must be tightened according to required torque values provided by manufacturer. Lastly refill coolant into overflow tank before running engines for sometime while checking any leakages or proper functioning relating to those car parts.