Coolant Flush

This procedure drains, flushes, and refills the cooling system on a 2007 Ram 3500 with the 5.9L Cummins diesel engine to maintain proper engine temperature and prevent corrosion.

Warnings

Tools required

Parts

• Radiator drain petcock or plug (if damaged) × 1 — Inspect during procedure
• Radiator cap (if damaged or worn) × 1 — Inspect during procedure

Fluids

• HOAT coolant 50/50 — 28 qt

Preparation

1. Ensure engine is completely cold to the touch
2. Park vehicle on level surface and engage parking brake
3. Position drain pan under radiator drain location on passenger side lower tank
4. Have approximately 28 quarts of HOAT 50/50 coolant available

Procedure

1. 1

   Remove radiator cap
   Slowly turn the radiator cap counterclockwise to the first stop to release any residual pressure. Wait for any hissing to stop, then press down and continue turning to remove the cap completely.
2. 2

   Drain radiator
   Locate the radiator drain petcock on the lower passenger side of the radiator. Turn the petcock counterclockwise to open and drain coolant into the drain pan. If equipped with a drain plug instead of petcock, remove the plug with appropriate socket.
3. 3

   Drain engine block
   Locate the engine block coolant drain plug on the block. Its exact position varies; consult the factory service manual as access can be obstructed by the starter, turbo, or exhaust components. Remove the drain plug and allow coolant to drain completely. On some configurations, there may be two block drain plugs (passenger and driver side).
   ℹ️Block drain location can be difficult to access. Use a socket with extension if needed.
4. 4

   Remove lower radiator hose (optional flush step)
   If performing a thorough flush, use pliers to move the hose clamp back on the lower radiator hose at the radiator connection. Remove the hose to allow complete drainage and flushing access. If only performing a drain and fill, skip to step 6.
5. 5

   Flush cooling system
   Insert garden hose into the radiator filler neck or upper radiator hose connection. Run water through the system until it runs clear from the lower radiator connection and block drain. This removes sediment and old coolant residue.
   ⚠Do not run the engine with plain water in the system. This is a static flush only.
6. 6

   Reinstall drain plugs and hoses
   Reinstall the engine block drain plug(s) securely. Close the radiator drain petcock by turning clockwise, or reinstall the radiator drain plug if equipped. If lower radiator hose was removed, reinstall it and position the hose clamp properly.
7. 7

   Fill cooling system
   Using a funnel, slowly pour HOAT 50/50 coolant into the radiator filler neck. Fill until coolant reaches the bottom of the filler neck. Pause periodically to allow air bubbles to escape. The radiator will only accept a portion of the total system capacity during initial fill; the remainder is added during burping. Verify total system capacity against the factory service manual for your specific configuration.
   ℹ️Fill slowly to minimize air pockets in the system. The 5.9L Cummins does not have a self-bleeding system.
8. 8

   Fill coolant recovery tank
   Fill the coolant recovery tank to the FULL COLD mark with HOAT 50/50 coolant.
9. 9

   Burp cooling system
   With the radiator cap still off, start the engine and allow it to idle. Watch the coolant level in the radiator and add coolant as needed as the thermostat opens and air purges from the system. Run until the engine reaches normal operating temperature and the upper radiator hose becomes hot.
   ⚠Monitor temperature gauge closely. If engine begins to overheat, shut off immediately and allow to cool before continuing.
10. 10

    Install radiator cap and final check
    With engine at operating temperature, shut off the engine. Allow to cool for 10 minutes, then top off the radiator to the bottom of the filler neck if needed. Install the radiator cap securely. Check the recovery tank level and adjust to FULL COLD mark.

Reassembly

1. Verify radiator cap is installed securely with proper seal
2. Ensure all drain plugs and hose connections are tight with no leaks
3. Wipe down any coolant spills on engine or frame components

Verification

• Start engine and verify no coolant leaks from radiator, hoses, or drain plugs
• Confirm coolant recovery tank is at FULL COLD mark with cold engine
• Monitor temperature gauge during test drive to ensure normal operating temperature
• After first heat cycle, recheck coolant level in radiator and recovery tank when cold
• Check coolant concentration with refractometer to verify proper 50/50 mix (freeze protection to approximately -34°F)

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