This procedure covers the removal and replacement of the coolant reservoir (overflow tank) on a 2012-2018 Jeep Wrangler JK with the 3.6L Pentastar V6 engine.

Warnings

Tools required

Parts

• Coolant reservoir tank × 1 — Mopar 68143543AB or equivalent
• Coolant reservoir cap (if damaged) × 1 — Use OEM specification

Fluids

• Mopar OAT Coolant (Purple) — 2 qt

Preparation

1. Ensure the engine is completely cold before beginning work
2. Park the vehicle on level ground and engage the parking brake
3. Place drain pan beneath the work area to catch coolant spillage
4. Locate the coolant reservoir on the passenger side of the engine bay, mounted to the inner fender well

Procedure

1. 1

   Release cooling system pressure
   Slowly rotate the coolant reservoir cap counterclockwise to release any residual pressure. Remove the cap completely and set aside. Even when cold, some pressure may be present.
2. 2

   Drain coolant from reservoir
   Position the drain pan directly under the coolant reservoir. Using needle-nose pliers, squeeze the hose clamp on the lower hose (connects reservoir to radiator) and slide it down the hose away from the reservoir nipple. Pull the lower hose off the reservoir and allow coolant to drain into the pan. The reservoir will not completely drain; some coolant will remain.
3. 3

   Disconnect upper hose
   Using needle-nose pliers, squeeze the hose clamp on the upper hose (connects to thermostat housing or overflow connection) and slide it down the hose. Pull the upper hose off the reservoir nipple. Additional coolant may drain out.
4. 4

   Remove reservoir mounting
   Locate the mounting tab at the bottom of the reservoir that inserts into a bracket on the inner fender. Lift the reservoir upward to disengage it from the lower mounting bracket. The reservoir may also have a push-pin or clip at the top; if present, use a flathead screwdriver to pry it out gently. Remove the reservoir from the engine bay.
5. 5

   Inspect hoses and connections
   Examine both hoses for cracks, splits, or deterioration. Check the reservoir nipples on the new reservoir for debris or damage. Inspect hose clamps for proper spring tension; replace if weak or corroded. Clean the hose ends with a shop towel if dirty.
6. 6

   Install new reservoir
   Position the new coolant reservoir into the engine bay. Align the lower mounting tab with the bracket on the inner fender and press down firmly to seat it. If equipped with a top mounting pin, press it into the fender hole until it clicks into place. Ensure the reservoir is secure and does not move when pulled.
7. 7

   Connect upper hose
   Push the upper hose firmly onto the reservoir nipple until it is fully seated (approximately 1 inch of engagement). Slide the hose clamp up to the reservoir neck and position it approximately 1/4 inch from the end of the nipple. Squeeze the clamp to ensure it is tight on the hose.
   Torque spec

   Hose Clamps4 Nm (3 lb-ft)
8. 8

   Connect lower hose
   Push the lower hose firmly onto the reservoir nipple until fully seated. Slide the hose clamp up to the reservoir neck and position it approximately 1/4 inch from the end of the nipple. Verify both hose connections are secure by attempting to pull them off with moderate force.
   Torque spec

   Hose Clamps4 Nm (3 lb-ft)
9. 9

   Refill cooling system
   Fill the coolant reservoir to the MAX or FULL COLD line with Mopar OAT Purple coolant. Do not overfill. Install the reservoir cap and tighten until it clicks or seats firmly. Start the engine and allow it to reach normal operating temperature (approximately 10 minutes). Monitor the temperature gauge to ensure it stays in the normal range.
10. 10

    Check for leaks and top off
    With the engine at operating temperature, visually inspect both hose connections at the reservoir for coolant leaks. Check around the reservoir mounting area for drips. Shut off the engine and allow it to cool for 15 minutes. Recheck the coolant level in the reservoir and add coolant if needed to reach the MAX line. Reinstall the cap.

Reassembly

1. Ensure both hose clamps are properly positioned and secure
2. Verify the reservoir cap is fully tightened and seated correctly
3. Wipe down the reservoir and surrounding area to remove any coolant residue
4. Double-check that the reservoir is firmly mounted and does not rattle or move

Verification

• Confirm coolant level is at the MAX (FULL COLD) line when the engine is cold
• Start the engine and verify no coolant leaks appear at either hose connection during warm-up
• Monitor the temperature gauge during a test drive to ensure normal operating temperature is maintained
• After the first drive cycle, recheck coolant level when cold and top off if necessary
• Inspect the ground under the vehicle after overnight parking for any coolant drips

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