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How to Check and Change Your Own Engine Coolant

Like the oil, your car’s coolant needs to be changed regularly. Your owner’s manual will provide a general guideline for scheduling coolant changes. Some automotive technicians believe engine coolant should be changed every 30-50 thousand miles.

Coolant Explained

Have you ever seen an old movie where someone pours water into the radiator of their overheating flivver? Modern coolant is a 1:1 mixture of antifreeze and water. The antifreeze lowers the freezing point of the water to -28° F while raising its boiling point to 275° F. Antifreeze doubles as a lubricant and mitigates the corrosive properties of water.

Important Safety Note

Before removing the radiator cap to check your coolant make sure the top of the radiator and the radiator hose are cool to the touch. Removing the cap on a hot or warm radiator can result in being scalded by a spray of hot liquid.

Testing Engine Coolant

You can, of course, have your coolant tested at a repair shop. For do-it-your-self types, there are a variety of coolant testers on the market ranging from less than $13.00 to a few hundred dollars. The lower-priced testers consist of a plastic housing with a hose on one end and a bulb on the other. You insert the hose in the radiator, squeeze the bulb to draw coolant into the housing where a group of check balls indicates the lowest freezing point for your coolant. A coolant hydrometer uses needles rather than check balls to indicate the lowest temperature your coolant can withstand on one side and the highest temperature it can withstand on the other side.

Check Coolant Color And Acidity

If upon visual inspection coolant appears a whitish-grey or has bits of rust in it the coolant needs changing. Obviously, acid circulating through your engine is not a desirable thing. The acidity of your coolant can be checked using a cup, litmus paper which is available at auto parts stores, and a turkey baster. Use the baster to transfer some coolant from the radiator to the cup then insert the litmus paper. For modern coolant, the ideal pH level is 8.3. Anything over 8.3 the engine coolant needs to be replaced.

Changing Your Own Coolant

You will need a jack, jack stands, a drain pan, slip-joint or hose clamp pliers, a clean pail, a jug of the coolant prescribed by your owner’s manual, and distilled water.

  1. Secure the vehicle on jack stands
  2. Place the drain pan under the radiator
  3. Remove the radiator cap or coolant tank pressure cap
  4. Remove the drain cock and lower radiator hose clamps
  5. Remove the radiator hose

After the coolant has drained into the pan replace the drain cock, radiator hose, and hose clamps. In the pail mix the ratio of distilled (not tap) water to coolant listed on the coolant container. Gradually add coolant until the level is an inch below the top of the radiator or several inches below the coolant reservoir ‘s full mark. Let the engine warm-up and when the coolant level drops top off the radiator or fills the coolant reservoir to the “hot” mark. Be sure to check for leaks.

Important Notes

If upon inspection your coolant shows evidence of corrosion or the coolant change is way overdue take your vehicle to a mechanic to have your cooling system flushed. Check the owner’s manual to see if your cooling system needs bleeding which requires the purchase of a special tool that costs around $80.00.