How to Maintain radiator upkeep and levels

How to Maintain radiator upkeep and levels

The radiator is arguably the most important part under the hood of your vehicle. It is the part that provides the cooling to your engine so that it does not overheat. Proper care of a radiator can extend the life of your stock, or factory, radiator long past its initial lifespan as well as the engine. Improper care of your radiator and cooling system can become expensive, costing you hundreds of dollars in repairs to the radiator system, and thousands of dollars if neglect of the radiator system damages engine components.

Before beginning work on the cooling system, you should have the following tools with you for the job.

Ratchet set (Metric or Standard depending on your vehicle.)

A complete screwdriver set, to include flathead and Phillips head screwdrivers.

Trouble light (fluorescent recommended for better viewing.)

Coolant system gauge.

Antifreeze and water source.

Drain pan.

Grease rags.

It’s a good idea to lay out these specific tools ahead of time near where you’ll be working. This way you can run a checklist and see that you have all the tools needed to do the job.


You’ll first want to inspect the cooling system. Starting with the radiator hoses, examine them for “dry-rot”. That is, look for a flaking or brittleness in the rubber hosing. Grab the hoses on both top and bottom and firmly, but not overly firm, squeeze the radiator hoses. If you feel any wetness or if flakes of rubber come off on your hands, that means the hose or hoses need to be replaced. Consult your local parts store for replacement hoses. When obtaining new hoses, be sure to obtain new hose clamps.

While checking the hoses, look for water leaks around where the hose marries with the radiator. If there is little water leaking out, take a Phillips head or Flat head screw driver and tighten down the hose clamps as tight as possible. This will seal that end of the connection. Be sure to also check the connection on the other ends that connect to the engine itself and tighten as necessary.

Next, inspect the radiator itself for cracks, holes and dents. Use of a flourescent trouble light is especially helpful here as the bright light exposes the cracks better than a regular light bulb. If not obscured, look on the back of the radiator grill that faces the engine as well as the front. Get down on the ground and look underneath, especially around the draincock for any damage to working parts there. If any minor holes are found, you might want to consider taking your vehicle to a radiator shop where those smaller holes can be welded shut.

Radiator coolant levels:

The coolant level in your automobile is critical to maintaining a cool engine that doesn’t overheat. Normal coolant/water levels in a vehicle are 50%/50%. In extreme cold environments, where you want added freezing protection, the recommended level is 70%/30%. Before filling your radiator, it’s a good idea to flush the radiator. That is, to drain and clear out any contaminents in the radiator itself to ensure proper function and flow of the antifreeze and water through your system.

Flushing the radiator:

With the engine cool, remove the radiator cap. Check the spring on the cap and make sure it’s not rusted, bent or broken. Also, inspect the gasket on the radiator cap for dry rot, cuts or missing parts of the gasket. If any of these things occur, you will need a new radiator cap. Next, locate the draincock on your radiator. This is located near the front and underneath the vehicle. Place a drain pan underneath the draincock and then open the draincock until the water starts flowing out at a steady stream.

Once the water and coolant has drained, close the draincock. Pour an entire bottle of radiator flush into the radiator, fill the rest of the radiator up with water, and then put the radiator cap back on securely. Next, start the engine and turn on the heater to high and let the car idle for 15-20 minutes. During this time, be sure to monitor your temperature gauge on your instrument display inside the car. The needle should stay between the H and C marks. If the needle moves into the red during this time, shut-off the vehicle immediately.

After the required 15-20 minutes have passed, turn off the ignition and let the engine cool for approximately 5 minutes. Then with a thick rag, remove the radiator cap and then open the draincock. Observe the water coming out of the radiator. If the color of the water is a very faint red color, then things are normal. If the color of the water is a heavy shade of red, you may need to flush the radiator again, as this is a sign that rust has set in. If several flushes do not get rid of the red in the water, you must replace the radiator. Once completely drained, close the draincock and then fill up the radiator completely with water, replace cap, and turn on ignition and let run for another 15-20 minutes.

Once time has passed, open the cap, drain the radiator of the water, and close the draincock. For refilling the radiator, auto parts stores today come with premixed antifreeze and water to refill your radiator on your vehicle. This is recommended, especially for novice D.I.Y. efforts. Pour in as many bottles as it takes to fill the radiator up to the brim of the fill hole. If you have an overfill reservoir, be sure to fill that to the proper level by noting the tick marks on the side of the reservoir. Replace the cap on the radiator, turn on ignition and let the vehicle run for at least one half hour.

If the temperature gauge stays between the H + C marks, then you are finished with the flush and refill. If the needle inches towards the hot zone, then add more 50/50 mix antifreeze until the needle settles steadily between the hot and cold zones. To measure the protection level, take one coolant system gauge, stick inside the fill hole, and squeeze the bulb. The number of balls floating at a single time, along with the temperature marks on the vial, will tell you how much protection, in both cold weather and hot weather, you have. This concludes the flush and refills instructions for your radiator.

Word of Caution! In maintaining your radiator between flushes, do not mix different brands of radiator mix. Different makers of coolant formulate their products differently than others, and mixing two different kinds can alter the protection level of your radiator, and may lead to mechanical breakdown of the cooling system. Always use the same brand and type of coolant in your vehicle every time you flush or fill.

Word of Caution!

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