What steps should be taken before assuming the thermostat is responsible for a cooling system problem on 2003 Mazda Protege?

Before blaming the thermostat, check coolant level, belt tension and gauge. Slow warm-up indicates stuck open; hot engine with cool lower hose indicates stuck closed. Driving without one worsens emissions and economy. To replace: disconnect negative, drain coolant, remove hose/cover, swap thermostat noting orientation, reassemble, refill and check leaks.

Genuine 2003 Mazda Protege Thermostat

Engine Coolant Thermostat

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2003 Mazda Protege Thermostat Part Number: KL01-15-171A-9U
$25.61 MSRP: $34.16
You Save: $8.55 (26%)
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Product Specifications
- Other Name: THERMOSTAT (W/GASKET)
- Replaces: 8AK2-15-171, 8AGX-15-171, FS05-15-171, KL01-15-171, KL01-15-171A
- Item Weight: 0.90 Pounds
- Condition: New
- Fitment Type: Direct Replacement
- SKU: KL01-15-171A-9U
- Warranty: This genuine part is guaranteed by Mazda's factory warranty.
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Fits the following 2003 Mazda Protege Submodels:
- DX, ES, LX, Mazdaspeed, MP3 | 4 Cyl 1.8 L GAS, 4 Cyl 2.0 L GAS

2003 Mazda Protege Thermostat Parts and Q&A

Q: What steps should be taken before assuming the thermostat is responsible for a cooling system problem on 2003 Mazda Protege?
A: Before blaming the thermostat, check coolant level, belt tension and gauge. Slow warm-up indicates stuck open; hot engine with cool lower hose indicates stuck closed. Driving without one worsens emissions and economy. To replace: disconnect negative, drain coolant, remove hose/cover, swap thermostat noting orientation, reassemble, refill and check leaks.