How to Repair a Nissan Thermostat

Any problems your Nissan vehicle's engine has in cooling can be a result of the thermostat. If you know the coolant level is good and the engine takes a long time to warm up, the thermostat is likely stuck open. If the engine is overheating and the radiator's upper hose doesn't feel hot, the thermostat is likely stuck closed. The only way to repair a thermostat is to replace it. Getting to the thermostat in the engine can vary depending on the model and engine type you have.

Difficulty: Challenging

Instructions

Things You'll Need:

• Wrench
• Container
• Pliers
• Screwdriver
• RTV sealant
• Thermostat
• Engine coolant
• Lacquer thinner

Accessing the Thermostat

1. Prepare for the replacement by disconnecting the negative battery cable and draining the engine coolant into a container--you need to remove the drain plug from the radiator first and then the drain plug at the engine block.

2. Remove the engine's cooling fan by loosening the fan/water pump pulley nuts, unclipping and removing the fan shroud's lower half, removing the water pump pulley nuts and pulling the fan out from underneath.

3. Disconnect all components blocking access to the thermostat by removing their bolts. On four-cylinder engines, this includes the air cleaner, air intake duct and the power steering pump's support bracket. On a 3.3 liter V6 or SOHC engine, remove the upper radiator hose from the intake manifold's coolant outlet.

4. Slip off the drive belts blocking the thermostat by turning their tensioner bolts with a wrench or breaker bar. On a 3.3 liter truck or DOHC engine, follow this by removing the upper idler pulley bracket. On a 3.5 liter engine, remove the water pump drain plug from the front end of the block.

5. Detach all hoses from the thermostat housing cover by loosening the hose clamps with pliers; this usually includes the lower radiator hose. This is only needed on V6 engines; you will keep the hose attached on a four-cylinder.

6. Remove the thermostat housing cover by removing its bolts. There will be some coolant spilling out when the gasket seal breaks.

Changing the Thermostat

7. Disconnect and remove the thermostat from its cover by removing its screws. Take note of how the thermostat is positioned within the cover.

8. Scrape away all traces of gasket or sealant from the housing and cover and clean the surfaces with lacquer thinner.

9. Apply RTV sealant around the edge of the thermostat cover. You need to re-install the cover within five minutes of applying this sealant.

10. Mount the new thermostat into the cover in the same position the old thermostat was in.

11. Re-install the thermostat cover and all other parts in reverse order of installation.

12. Wait a half hour for the RTV sealant to cure before refilling the engine coolant. Use fresh coolant if the old coolant is contaminated.

References

• Chilton Nissan Pick-Ups Repair Manual; Jeff Kibler: 2004
• Chilton Nissan Maxima Repair Manual; Bob Henderson; 2004

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