How to Replace the Thermostat in a 1995 Infiniti Q45

Infiniti --- Nissan's luxury division --- released the Q45 full-size luxury sedan in the 1989 model year. The 1995 Q45 came fitted with a 4.5-liter V-8 engine, keeping the Infiniti tradition of using the engine size in the name. This engine produced 278-horsepower and 292 foot-pounds of torque, both of which were relatively high for the era. The thermostat in this V-8 engine helped keep the engine's operating temperature near 169 degrees Fahrenheit. Replacing the thermostat is a straightforward process, once you remove the ornament cover from the front of the engine.

Instructions

1

Raise the front of the Q45 off the ground, using a floor jack, and position jack stands under the vehicle's subframe. Lower the Q45 onto the jack stands.

2

Crawl beneath the Q45 and locate the radiator petcock --- drain plug --- under the lower radiator hose. Position a drain pan under the petcock and open the petcock to drain the coolant into the drain pan. Close the petcock once the coolant stops draining.

3

Raise the Q45 off the jack stands with a floor jack. Remove the jack stands from under the Infiniti and lower the car to the ground.

4

Remove the bolts securing the plastic ornament cover on the front of the engine, using a ratchet and socket. Pull the ornament cover off the engine, exposing the upper radiator hose below it.

5

Trace the upper radiator hose until you reach the thermostat housing --- the metal connecting point between the upper radiator hose and the engine. Remove the three bolts securing the thermostat housing to the engine, using a ratchet and socket, and pull the housing from the engine.

6

Notate the positioning of the thermostat in the engine and pull it from the engine.

7

Scrape the debris from the mating surface on the thermostat housing and the engine, using a plastic gasket scraper. Do not use a metal scraper, as it can damage the mating surface and cause a leak.

8

Insert a new thermostat into the engine in the same position the old thermostat was in.

9

Place a thin bead of RTV silicone around the new thermostat gasket and position it on the engine, make certain to line up the bolt holes on the gasket with those on the engine.

10

Set the thermostat housing back on the engine and tighten the three bolts to 14 foot-pounds, using a torque wrench and socket.

11

Reinstall the ornament cover on the front of the engine and tighten its bolts, using a ratchet and socket.

Filling and Bleeding the Cooling System

12

Start the Q45's engine. Open the radiator cap and pour in 50-50 premixed coolant until the level reaches the bottom of the radiator filler neck.

13

Allow the vehicle to reach normal operating temperature and add coolant each time the level drops --- the level drops as coolant displaces air throughout the cooling system. Tighten the radiator cap and turn the engine off.

14

Wait for the Infiniti's engine to cool. Open the radiator cap and fill the radiator with 50-50 premixed coolant until the coolant level reaches the bottom of the filler neck, if needed. Tighten the radiator cap.

15

Open the coolant overflow bottle and fill it with 50-50 premixed coolant until the level is between the "Max" and "Min" lines on the reservoir. Close the lid on the coolant overflow bottle. In total, the 1995 Q45's cooling system holds 2.7 gallons of 50-50 premixed coolant.