How to Replace Thermostat 2012-2018 Nissan Altima 2.5L L4
Difficulty: Intermediate · About 90 min · Nissan Altima
Replace the engine thermostat on the 2.5L four-cylinder Altima only after confirming the exact cooling-system component and service procedure by VIN. Work on a fully cold engine, renew the seal, refill with the specified coolant, and remove air from the system.
Tools you will need
- Metric socket set and ratchet
- Pliers
- Drain pan
- Funnel
- Cooling-system vacuum filler or bleed equipment if specified
- Safety glasses
- Gloves
Parts and supplies
- Thermostat matched to the VIN and engine
- New thermostat O-ring or seal
- Correct Nissan-approved coolant
Steps
Confirm the thermostat and prepare
Use the VIN and engine code to identify the correct thermostat location, seal, coolant type, and bleeding procedure. Park on level ground and let the engine cool completely before opening any part of the cooling system.
Drain enough coolant
Place a drain pan under the radiator and open the specified drain point or disconnect the hose named in the service procedure. Capture the coolant safely and keep it away from children and animals.
Remove the coolant inlet
Access the thermostat housing, disconnect the lower radiator hose if the procedure calls for it, and remove the coolant inlet fasteners. Lift away the inlet and thermostat without gouging the sealing surfaces.
Prepare the replacement
Compare the new thermostat with the removed unit and install a fresh O-ring or seal. Set the thermostat in the specified orientation; on the QR25DE procedure, the jiggle valve faces upward.
Reassemble the housing
Seat the thermostat and seal evenly, reinstall the coolant inlet, and tighten its fasteners to the vehicle's specification. Reconnect the hose and any components removed for access.
Refill and bleed the cooling system
Refill with the exact approved coolant and use the vehicle-specific air-bleeding procedure. Do not assume the system is full just because the reservoir level rises; trapped air can cause overheating.
Check for leaks and stable temperature
Start the engine and monitor coolant temperature while checking the housing and hose joints for leaks. Let the engine cool before rechecking the level, and stop if it overheats or the cabin heater output indicates trapped air.
Check your vehicle’s repair manual for exact specifications and fit.