Coolant Reservoir

This procedure covers the removal and replacement of the coolant reservoir on a 2007 Ram 3500 with the 5.9L Cummins diesel engine.

Warnings

Tools required

Parts

• Coolant reservoir tank × 1 — Use OEM specification
• Coolant reservoir cap (if damaged) × 1 — Use OEM specification

Fluids

• HOAT coolant 50/50 — 2 qt

Preparation

1. Ensure engine is completely cool to the touch
2. Park vehicle on level ground and engage parking brake
3. Open hood and prop securely
4. Place drain pan beneath the passenger side of the engine bay to catch coolant spillage

Procedure

1. 1

   Release cooling system pressure
   Slowly turn the pressurized coolant reservoir cap counterclockwise to the first stop to release residual system pressure. Listen for hissing and wait until all pressure is released, then press down and continue turning counterclockwise to remove the cap completely and set aside. Listen for hissing and wait until all pressure is released before fully removing the cap. Remove the cap completely and set aside.
2. 2

   Drain coolant from reservoir
   Position the drain pan directly under the coolant reservoir. Using a flathead screwdriver or hose clamp pliers, loosen the hose clamp on the coolant supply/return hose at the bottom of the reservoir. Carefully pull the hose off the reservoir nipple and allow coolant to drain into the pan. Carefully pull the hose off the reservoir nipple and allow coolant to drain into the pan. You may need to tilt or squeeze the reservoir to fully drain it.
3. 3

   Disconnect upper overflow hose
   Locate the small overflow hose connected to the upper portion of the reservoir (typically runs to the radiator). Loosen the hose clamp and disconnect the hose from the reservoir. Be prepared for a small amount of coolant to spill.
4. 4

   Remove reservoir mounting fasteners
   The reservoir is secured to the inner fender with either two or three plastic push-pin fasteners or bolts. Identify the fastener type. For push-pins, use a flathead screwdriver to pry up the center pin, then remove the entire fastener. For bolts, remove them completely. Support the reservoir with your other hand as you remove the final fastener.
5. 5

   Remove coolant reservoir
   Carefully lift the coolant reservoir up and out of the engine bay. Tilt it as needed to clear surrounding components. Be careful not to spill remaining coolant on engine components or belts. Empty any remaining coolant into your drain pan.
6. 6

   Clean mounting area and inspect hoses
   Wipe down the mounting area on the inner fender with a shop rag. Inspect both coolant hoses for cracks, swelling, or damage. Replace any questionable hoses. Check that hose clamps are in good condition and not rusted or stripped.
7. 7

   Install new coolant reservoir
   Position the new reservoir into the mounting location on the inner fender. Align the mounting holes and install the mounting fasteners. For push-pins, press the body in first, then push the center pin down until flush. Ensure the reservoir is secure and does not move excessively.
8. 8

   Reconnect coolant hoses
   Attach the lower radiator hose to the bottom nipple of the reservoir and secure with the hose clamp. Connect the upper overflow hose and secure its clamp. Ensure both hoses are pushed fully onto the nipples and clamps are positioned properly over the hose beads.
9. 9

   Refill cooling system
   Fill the coolant reservoir with fresh Mopar HOAT (G-05) 50/50 coolant mixture to the FULL COLD mark on the reservoir. Do not overfill. Install the reservoir cap and turn clockwise until it clicks or stops firmly.
10. 10

    Bleed cooling system and check for leaks
    Start the engine and allow it to reach normal operating temperature with the heater on full hot. Monitor the coolant level and add coolant as needed as air purges from the system. Watch for leaks around both hose connections. After reaching operating temperature, shut off engine and allow to cool. Recheck coolant level when cold and top off to FULL COLD mark if needed.

Reassembly

1. Ensure all hose clamps are tight and properly positioned
2. Verify reservoir cap is installed securely
3. Clean up any spilled coolant from engine bay and undercarriage

Verification

• Check that coolant level is at FULL COLD mark when engine is cold
• Verify no coolant leaks are present at either hose connection
• Confirm reservoir is securely mounted and does not move or rattle
• Test reservoir cap for proper seal by gently pulling up on it after installation
• After first drive cycle, recheck coolant level and inspect for leaks

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