How to Fix an Oil Filled Radiator

Written by paul vaughn
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Oil in the radiator is usually caused by a blown head gasket between the engine head and engine block. In this condition, the coolant ports and the oil ports are no longer separated allowing to to mix with engine coolant and coolant to mix with engine oil. In either case, before running the engine again both problems must be corrected. This article will cover the radiator flushing and refilling.

Skill level:
Moderately Challenging

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Things you need

  • 5-gallon drain pan
  • Pressure washer
  • OSHA approved coolant disposal container
  • Large-bladed flathead screwdriver
  • Safety glasses
  • Novax gloves

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  1. 1

    Place a drain pan under the drain valve at the bottom of the radiator. Make sure the engine is cool before beginning. Open the cap on the coolant overflow container and allow all the coolant mixed with oil to drain into the drain pan.

  2. 2

    Locate the clamps on the top and bottom radiator hoses.There are two 1-inch lines at the top and bottom of the radiator. The top one is the outlet to the engine and the bottom is the return from the engine. Loosen both clamps with a screwdriver by turning them counterclockwise.

  3. 3

    Allow gravity to drain the fluid from the radiator. You may need to remove a plastic cover that runs across the front of the engine compartment to get to the cap. Check the service manual for the specific procedures for removing the cover.

  4. 4

    Start the pressure washer and put the tip into the radiator pressure cap. Pull the trigger and allow the pressurised water to flush out the oil. Continue until the water runs clean out of the drain valve.

  5. 5

    Close the drain valve by turning it clockwise by hand until tight and refill the radiator with coolant to the full line on the overflow container. See the service manual for its location.

  6. 6

    Tighten the clamps with the screwdriver.

  7. 7

    Let the engine run with the heater on so the heater core will fill with coolant. The fluid level will drop in the overflow container. Add coolant as needed until the level no longer drops and the fluid level is steady on the full line.

Tips and warnings

  • Take your time when doing this procedure. It will take a while to get all the oil out. The radiator is full of small inlet and outlet valves that are easily plugged and take a while to clear.
  • Be careful what you touch when the engine is running. The coolant will quickly become hot enough to cause serious injury. You should wear gloves and safety glasses through this procedure.

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