Drain the radiator, drain the engine block, refill with Nissan Long Life Antifreeze (blue) pre-diluted 50/50. R51 VQ40DE holds about 10.6 quarts total. Burp it twice — once cold, once hot — or you will warp a head.
Nissan moved from green coolant to blue (Long Life Antifreeze) for the 2010 model year. The two are chemically compatible — you do not need to flush every trace of green before adding blue. The interval also extended: green wants a service at 30,000 miles after the first 60,000-mile fill, blue stretches to 105,000 miles or 7 years.
The VQ40DE is famously fussy about air pockets. The thermostat housing sits high, the heater core sits higher, and the system has no factory bleeder screw. If you skip the burp procedure, the trapped air pocket boils against the thermostat, the thermostat never opens, and the engine cooks. This is not theoretical — it is the most common cause of post-flush head gasket failure on R51s.
VG33E (R50) and VG30E (WD21) are forgiving by comparison. The cooling system on these older engines bleeds through the heater core with the heater set to max and a few cycles to operating temp. Still good practice to use a vacuum fill tool — it is $40, it pulls coolant in under negative pressure, and it eliminates burping entirely on any platform.
The radiator drain on all three engines is a plastic petcock at the bottom-passenger corner of the radiator. The petcock is brittle on any Pathfinder over 100,000 miles. Treat it gently — a cracked petcock turns this $40 job into a $400 radiator replacement. If yours snaps, OEM Nissan radiators are still in production at parts.nissanusa.com.
The engine block drains live on each side of the block on the VQ40DE — small hex plugs (10mm) above the oil pan flange, one per bank. Most weekend flushes skip the block drains. If you only drain the radiator, you replace roughly 5 quarts of the 10.6-quart system. For a full flush, you must drain the block too.
| Part | Vendor | Est. price |
|---|---|---|
| Nissan Long Life Antifreeze (Blue, pre-diluted, 1 gallon) | Nissan | ~$28 |
| Distilled water (1 gallon, for top-off) | Any grocery store | ~$2 |
| Radiator cap (if old or weeping) | Nissan | ~$14 |
Written and maintained by an AZ wheeler and driveway wrencher. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.