Complete coolant system drain, flush, and refill procedure for the 2012-2018 Jeep Wrangler JK with 3.6L V6 engine, including air purge process.

Warnings

Tools required

Parts

• Radiator drain petcock (if damaged) × 1 — Use OEM specification

Fluids

• Mopar OAT Coolant (Purple) — 13 qt

Preparation

1. Ensure engine is completely cold (minimum 2 hours after last operation)
2. Park vehicle on level ground and set parking brake
3. Verify you have sufficient Mopar OAT purple coolant (approximately 13 quarts total)
4. Place drain pan under radiator drain location on passenger side lower radiator tank

Procedure

1. 1

   Remove radiator cap
   Slowly rotate the radiator cap counterclockwise to the first detent and allow any residual pressure to release. Once pressure is released, press down and continue rotating to remove cap completely.
2. 2

   Drain coolant from radiator
   Locate the drain petcock on the lower passenger side of the radiator. Turn the petcock counterclockwise to open and allow coolant to drain into the drain pan. Allow system to drain completely (approximately 10-15 minutes).
   ⚠Coolant will flow quickly once petcock is opened - ensure drain pan is properly positioned
3. 3

   Drain engine block
   Locate the engine block drain plug on the driver side of the block, below the exhaust manifold. Remove the drain plug using appropriate socket and allow engine block coolant to drain completely. Inspect drain plug threads and washer for damage.
4. 4

   Close drain points
   Reinstall the engine block drain plug with washer and tighten securely. Close the radiator drain petcock by turning clockwise until hand tight, then apply torque wrench to specification.
   Torque spec

   Drain Petcock8 Nm (6 lb-ft)
5. 5

   Prepare cooling system for fill
   Locate the coolant bottle bleed screw on top of the coolant reservoir. Open the bleed screw by turning counterclockwise approximately 2-3 turns. This screw must remain open during the entire filling process to allow air to escape.
   ℹ️The bleed screw is critical for proper air purge - do not skip this step
6. 6

   Fill cooling system at radiator
   Using a funnel, slowly pour Mopar OAT purple coolant (50/50 premix or properly mixed concentrate) into the radiator fill neck. Fill slowly to allow air to escape through the reservoir bleed screw. Continue filling until coolant reaches the base of the radiator fill neck and coolant flows from the reservoir bleed screw.
7. 7

   Fill coolant reservoir
   Continue adding coolant to the coolant reservoir until the level reaches the MAX cold fill line. Watch for coolant flow from the bleed screw, which indicates air is being purged from the system.
8. 8

   Close bleed screw
   Once coolant flows steadily from the bleed screw without air bubbles, close the bleed screw by turning clockwise and tighten to specification using torque wrench.
   Torque spec

   Bleed Screw8 Nm (6 lb-ft)
9. 9

   Install radiator cap and initial burp
   Install the radiator cap hand tight. Start the engine and allow it to idle with heater set to maximum temperature and fan speed. Monitor engine temperature gauge. Run engine until cooling fans cycle on and off at least twice (approximately 15-20 minutes).
   ⚠Monitor temperature gauge constantly - if gauge approaches red zone, shut off engine immediately and allow to cool
10. 10

    Final air purge
    With engine still running at operating temperature, carefully remove radiator cap (use shop towel for protection). Coolant level should have dropped. Add additional coolant to bring level back to base of fill neck. Rev engine to 2500 RPM several times to help purge remaining air. Reinstall radiator cap.
    ⚠️Use extreme caution when removing cap from hot system - use shop towel and turn slowly to first detent to release pressure before fully removing
11. 11

    Verify coolant level after cool down
    Allow engine to cool completely (minimum 2 hours). Check coolant reservoir level when cold - it should be at the MAX cold fill line. Top off if necessary. Check radiator level by removing cap - coolant should be at base of fill neck.

Reassembly

1. Ensure radiator cap is properly installed and seated
2. Verify all drain points are closed and torqued properly
3. Wipe down any coolant spills on engine or frame components
4. Dispose of old coolant properly at approved recycling facility

Verification

• Check for coolant leaks around drain petcock, block drain plug, and all hose connections
• Verify coolant reservoir is at MAX cold fill line when engine is cold
• Start engine and verify heater produces hot air at idle
• Monitor for proper engine operating temperature (approximately 195-220°F) during test drive
• Recheck coolant level after first drive cycle and top off if necessary
• Inspect ground under vehicle after overnight parking for any coolant leaks

More procedures for this vehicle